Photosynthesis-antenna Proteins Research Articles

Integrated Transcriptome and Proteome Analysis Revealed the Regulatory Mechanism of Hypocotyl Elongation in Pakchoi.

Hypocotyl length is a critical determinant for the efficiency of mechanical harvesting in pakchoi production, but the knowledge on the molecular regulation of hypocotyl growth is very limited. Here, we report a spontaneous mutant of pakchoi, lhy7.1, and identified its characteristics. We found that it has an elongated hypocotyl phenotype compared to the wild type caused by the longitudinal growth of hypocotyl cells. Different light quality treatments, transcriptome, and proteomic analyses were performed to reveal the molecular mechanisms of hypocotyl elongation. The data showed that the hypocotyl length of lhy7.1 was significantly longer than that of WT under red, blue, and white lights but there was no significant difference under dark conditions. Furthermore, we used transcriptome and label-free proteome analyses to investigate differences in gene and protein expression levels between lhy7.1 and WT. At the transcript level, 4568 differentially expressed genes (DEGs) were identified, which were mainly enriched in "plant hormone signal transduction", "photosynthesis", "photosynthesis-antenna proteins", and "carbon fixation in photosynthetic organisms" pathways. At the protein level, 1007 differentially expressed proteins (DEPs) were identified and were mainly enriched in photosynthesis-related pathways. The comprehensive transcriptome and proteome analyses revealed a regulatory network of hypocotyl elongation involving plant hormone signal transduction and photosynthesis-related pathways. The findings of this study help elucidate the regulatory mechanisms of hypocotyl elongation in lhy7.1.

Over-activation of cold tolerance in arabidopsis causes carbohydrate shortage compared with Chorispora bungeana

Many plants cope with cold stress by developing acquired freezing tolerance (AFT) through cold acclimation (CA), and some species have strong basal freezing tolerance (BFT) independent of CA. Although CA has been extensively studied, its potential in agricultural applications is still unclear. Here, carbohydrate metabolism and transcriptome in AFT plant Arabidopsis and BFT plant Chorispora bungeana were compared with each other. The results showed that, although both species were able to accumulate soluble sugars during CA, leaf starch accumulation in the daytime was almost blocked in Arabidopsis while it was greatly enhanced in C. bungeana, revealing that Arabidopsis experienced carbohydrate shortage during CA. Transcriptome and pathway enrichment analysis found that genes for photosynthesis antenna proteins were generally repressed by cold stress in both species. However, cold-up-regulated genes were enriched in protein translation in Arabidopsis, whilst they were enriched in carotenoid biosynthesis, flavonoid biosynthesis, and beta-amylases in C. bungeana. Furthermore, weighted gene co-expression network analysis (WGCNA) showed that the inhibition of starch accumulation was associated with down-regulation of genes for photosynthesis antenna proteins and up-regulation of genes for protein translation, DNA repair, and proteasome in Arabidopsis but not in C. bungeana. Taken together, our results revealed that over-activation of common tolerant mechanisms resulted in insufficient carbohydrate supplies in Arabidopsis during CA, and photoprotective mechanisms played important roles in cold adaptation of C. bungeana. These findings uncovered the drawback of CA in improving freezing tolerance and highlighted photoprotection as a possible solution for agricultural applications.

Gene co-expression networks unravel the molecular responses of freshwater hydrophytes to combined stress of salinity and cadmium

Salinization in freshwater lakes is becoming a serious global environmental problem, especially in lakes of plateaus such as south-western plateau of China. However, limited information is available about the molecular response of freshwater hydrophytes to salinity under multiple stress. In the present study, a weighted gene co-expression network (WGCNA) was used to identify the modules of co-expressed genes in the physiological and biochemical indicators of Pistia stratiotes to determine its molecular response to salinity (NaCl) alone and when combined with cadmium (Cd). The physiological and biochemical indicators showed that P. stratiotes improved its salt tolerance by enhancing photosynthetic abilities, reducing oxidative stress, and inducing osmoprotectant generation. Morever, addition of NaCl reduced the Cd accumulation in P. stratiotes. Transcriptome and WGCNA analysis revealed that the pathways of alpha-linolenic acid metabolism, ribosomal, flavonoid biosynthesis, and phenylpropanoid biosynthesis were significantly enriched in both treatments. Genes associated with photosynthesis-antenna proteins, nitrogen metabolism, and the acid cycle pathways were only expressed under salinity stress alone, while the proteasome pathway was only significantly enriched in the combined salinity and Cd treatment. Our findings provide novel insights into the effects of salinization on aquatic plants in freshwater ecosystems and the management of aquatic ecosystems under global change.

Physiological and molecular responses of Trollius chinensis seedlings to waterlogging stress and subsequent drainage

Waterlogging led by extreme rainfall events is one of the major natural disasters under the global climate change context, putting plants under water stress. However, systematical studies on the response mechanisms in leaves to waterlogging are limited. We explored major leaf characteristics of oxidative stress and scavenging, photosynthesis, and osmotic regulations of Trollius chinensis. Two levels of waterlogging serverities (moderate level, W1, and severe level, W2) were studied on the 1st (D1), 5th (D5), 10th (D10), and 15th day (D15) upon waterlogging and on the subsequent 10th day after drainage (R10). In addition, based on physiological indicators, the leaves in control and W2 on D10 were selected for RNA-Seq. We found that most of physiological characteristics presented the greatest differences between control and waterlogging groups on D10 such as O2.-, SOD, and proline, while some other characteristics such as H2O2, POD, and GR showed highest change from control on D15. Furthermore, on R10, most of the physiologcial characteristics recovered in different levels, which indicates that this species is relative waterlogging-tolerant. The results also showed that out of 1182 differentially expressed genes (307 up-regulated and 875 down-regulated) obtained in W2 vs control, ‘photosynthesis’, ‘plastid’, ‘chloroplast’, ‘thylakoid’, and ‘chlorophyll-binding’ were the Gene Ontology (GO) enrichment hotspots, and ‘photosynthesis’, ‘photosynthesis-antenna proteins’, and ‘carbon fixation in photosynthetic organisms’ were the most enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The expression of genes related to the photosynthesis, amylase, calcineurin interacting protein kinases (CIPKs), glutathione-S-transferase (GST), and ethylene response factor (ERF) decreased, while the expression of some genes related to antioxidation, osmoregulation, and transcription factors belonging to MYB (Myb proto-oncogene protein) and NAC ((NAM, ATAF1/2, and CUC2) families increased, implying that these genes play key roles in T. chinensis to cope with waterlogging stress. We conclude that T. chinensis is a waterlogging-tolerant species and 10 days of severe waterlogging has induced changes of antioxidant, photosynthesis, and osmoregulation in physiological and transcriptome level. The present study provides candidate genes that can be used for waterlogging-resistant breeding in T. chinensis.

Integrated transcriptomic and metabolomic analysis reveals the molecular basis of tissue-specific accumulation of bioactive steroidal alkaloids in Fritillaria unibracteata

Fritillaria unibracteata is an endangered medicinal plant whose bulb has been used as a Chinese herb to suppress cough, asthma and excessive phlegm for centuries. Steroidal alkaloids, which are synthesized via the steroid synthesis pathways, are their significant bioactive constituents. However, few studies on genes involved in steroidal alkaloid biosynthesis in F. unibracteata have been reported, mainly due to the lack of the F. unibracteata genome. In this paper, comparative transcriptomic and metabolomic analyses of four different tissues of F. unibracteata (leaves, flowers, stems, and bulbs) were performed. Imperialine, peiminine, and peimisine were among the significant bioactive compounds that were considerably abundant in bulb tissue, according to the metabolomic findings. Then, 83.60 Gb transcriptome sequencing of four different tissues was performed, of which one gene encoding phosphomevalonate kinase was directly functionally characterized to verify the accuracy of sequences obtained from the transcriptome. A total of 9217 differentially expressed unigenes (DEGs) were identified in four different tissues of F. unibracteata. GO and KEGG enrichments revealed that phenylpropanoid biosynthesis, MVA-mediated terpenoid backbone biosynthesis, and steroid biosynthesis were enriched in bulb tissue, whereas enrichment of MEP-mediated terpenoid backbone biosynthesis, photosynthesis, photosynthesis-antenna protein and carotenoid biosynthesis was observed in aerial tissues. Moreover, clustering analysis indicated that the downstream steroid biosynthesis pathway was more important in steroidal alkaloid biosynthesis compared to the upstream terpenoid backbone biosynthesis pathway. Hence, MVA-mediated biosynthesis of steroidal alkaloids was proposed, in which 15 bulb-clustered DEGs were positively correlated with a high accumulation of bioactive steroid alkaloids, further validating our proposal. In addition, 36 CYP450s showing a positive correlation with bioactive steroidal alkaloids provided candidate enzymes to catalyze the subsequent steps of steroidal alkaloid biosynthesis. In addition, the transcription factors and ABC transporters clustered in bulb tissue might be responsible for the regulation and transportation of steroidal alkaloid biosynthesis. Protein-protein interaction analysis implied a highly complex steroid alkaloid biosynthesis network in which delta (24)-sterol reductase might be one of the central catalysts. Based on the integrated transcriptome and metabolome, this current study is a first step in understanding the tissue-specific biosynthesis of steroidal alkaloids in F. unibracteata. Furthermore, key genes and regulators identified herein could facilitate metabolic engineering to improve steroidal alkaloids in F. unibracteata.

Physiological and transcriptomic analysis reveal the crucial factors in heat stress response of red raspberry 'Polka' seedlings.

With global climate warming, recurring extreme heat and high temperatures irreversibly damage plants. Raspberries, known for their nutritional and medicinal value, are in high demand worldwide. Thus, it is important to study how high-temperature stress (HTS) affects raspberries. The physiological and biochemical responses and molecular genetic mechanisms of raspberry leaves to different HTS treatments were investigated: mild high temperature at 35°C (HT35), severe high temperature at 40°C (HT40), and the control at room temperature of 25°C (CK). The physiological results suggested that leaves in both the 35°C and 40°C treatments showed maximum relative conductivity at 4d of stress, increasing by 28.54% and 43.36%, respectively, compared to CK. Throughout the stress period (0-4 d), malondialdehyde (MDA) and soluble protein contents of raspberry leaves increased under HT35 and HT40 treatments, while soluble sugar content first decreased and then increased. Catalase (CAT) activity increased, superoxide dismutase (SOD) activity first increased and then decreased, and peroxidase (POD) activity gradually decreased. Photosynthetic and fluorescence responses of raspberry leaves showed the most severe impairment after 4d of stress. Transcriptomics results revealed significant alterations in 42 HSP family genes, two SOD-related differentially expressed genes (DEGs), 25 POD-related DEGs, three CAT-related DEGs, and 38 photosynthesis-related DEGs under HTS. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that these DEGs were mainly enriched in photosynthesis-antenna proteins, pentose and glucuronide interconversion, phenylpropane biosynthesis, and indole alkaloid biosynthesis. HTS induced excessive ROS accumulation in raspberry leaves, causing oxidative damage in plant cells and subsequently reducing photosynthesis in raspberry leaves. This reduction in photosynthesis, in turn, affects photosynthetic carbon fixation and starch and sucrose metabolism, which, combined with phenol propane biosynthesis, mitigates the HTS-induced damage.

Transcriptome analysis reveals the mechanism of different fruit appearance between apricot (Armeniaca vulgaris Lam.) and its seedling.

Apricot fruit has great economic value. In the process of apricot breeding using traditional breeding methods, we obtained a larger seedling (named Us) from the original variety (named U). And Us fruit is larger than U, taste better. Therefore, revealing its mechanism is very important for Apricot breeding. In this study, de novo assembly and transcriptome sequencing (RNA-Seq) was used to screen the differently expressed genes (DEGs) between U and Us at three development stages, including young fruits stage, mid-ripening stage and mature fruit stage. The results showed that there were 6,753 DEGs at different sampling time. "Cellulose synthase (UDP-forming) activity" and "cellulose synthase activity" were the key GO terms enriched in GO, of which CESA and CSL family played a key role. "Photosynthesis-antenna proteins" and "Plant hormone signal transduction" were the candidate pathways and lhca, lhcb, Aux/IAA and SAUR were the main regulators. The auxin signaling pathway was active in Us, of which Aux/IAAs and SAUR were the key fruit size regulators. The low level of lhca and lhcb in Us could reveal the low demand for exogenous carbon, but they increased at mature stage, which might be due to the role of aux, who was keeping the fruit growing. Aux and photosynthesis maight be the main causes of appearance formation of Us fruits. Interestingly, the higher expression of CESA and CSL proved that Us entered the hardening process earlier than U. The advanced developmental progress might also be due to the role of Aux.

Transcriptomic, Physiological, and Metabolomic Response of an Alpine Plant, Rhododendron delavayi, to Waterlogging Stress and Post-Waterlogging Recovery.

Climate change has resulted in frequent heavy and prolonged rainfall events that exacerbate waterlogging stress, leading to the death of certain alpine Rhododendron trees. To shed light on the physiological and molecular mechanisms behind waterlogging stress in woody Rhododendron trees, we conducted a study of Rhododendron delavayi, a well-known alpine flower species. Specifically, we investigated the physiological and molecular changes that occurred in leaves of R. delavayi subjected to 30 days of waterlogging stress (WS30d), as well as subsequent post-waterlogging recovery period of 10 days (WS30d-R10d). Our findings reveal that waterlogging stress causes a significant reduction in CO2 assimilation rate, stomatal conductance, transpiration rate, and maximum photochemical efficiency of PSII (Fv/Fm) in the WS30d leaves, by 91.2%, 95.3%, 93.3%, and 8.4%, respectively, when compared to the control leaves. Furthermore, the chlorophyll a and total chlorophyll content in the WS30d leaves decreased by 13.5% and 16.6%, respectively. Both WS30d and WS30d-R10d leaves exhibited excessive H2O2 accumulation, with a corresponding decrease in lignin content in the WS30d-R10d leaves. At the molecular level, purine metabolism, glutathione metabolism, photosynthesis, and photosynthesis-antenna protein pathways were found to be primarily involved in WS30d leaves, whereas phenylpropanoid biosynthesis, fatty acid metabolism, fatty acid biosynthesis, fatty acid elongation, and cutin, suberin, and wax biosynthesis pathways were significantly enriched in WS30d-R10d leaves. Additionally, both WS30d and WS30d-R10d leaves displayed a build-up of sugars. Overall, our integrated transcriptomic, physiological, and metabolomic analysis demonstrated that R. delavayi is susceptible to waterlogging stress, which causes irreversible detrimental effects on both its physiological and molecular aspects, hence compromising the tree's ability to fully recover, even under normal growth conditions.

Integrated transcriptome and microRNA sequencing analyses reveal gene responses in poplar leaves infected by the novel pathogen bean common mosaic virus (BCMV).

Recently, a novel poplar mosaic disease caused by bean common mosaic virus (BCMV) was investigated in Populus alba var. pyramidalis in China. Symptom characteristics, physiological performance of the host, histopathology, genome sequences and vectors, and gene regulation at the transcriptional and posttranscriptional levels were analyzed and RT-qPCR (quantitative reverse transcription PCR) validation of expression was performed in our experiments. In this work, the mechanisms by which the BCMV pathogen impacts physiological performance and the molecular mechanisms of the poplar response to viral infection were reported. The results showed that BCMV infection decreased the chlorophyll content, inhibited the net photosynthesis rate (Pn) and stomatal conductance (Gs), and significantly changed chlorophyll fluorescence parameters in diseased leaves. Transcriptome analysis revealed that the expression of the majority of DEGs (differentially expressed genes) involved in the flavonoid biosynthesis pathway was promoted, but the expression of all or almost all DEGs associated with photosynthesis-antenna proteins and the photosynthesis pathway was inhibited in poplar leaves, suggesting that BCMV infection increased the accumulation of flavonoids but decreased photosynthesis in hosts. Gene set enrichment analysis (GSEA) illustrated that viral infection promoted the expression of genes involved in the defense response or plant-pathogen interaction. MicroRNA-seq analysis illustrated that 10 miRNA families were upregulated while 6 families were downregulated in diseased poplar leaves; moreover, miR156, the largest family with the most miRNA members and target genes, was only differentially upregulated in long-period disease (LD) poplar leaves. Integrated transcriptome and miRNA-seq analyses revealed 29 and 145 candidate miRNA-target gene pairs; however, only 17 and 76 pairs, accounting for 2.2% and 3.2% of all DEGs, were authentically negatively regulated in short-period disease (SD) and LD leaves, respectively. Interestingly, 4 miR156/SPL (squamosa promoter-binding-like protein) miRNA-target gene pairs were identified in LD leaves: the miR156 molecules were upregulated, but SPL genes were downregulated. In conclusion, BCMV infection significantly changed transcriptional and posttranscriptional gene expression in poplar leaves, inhibited photosynthesis, increased the accumulation of flavonoids, induced systematic mosaic symptoms, and decreased physiological performance in diseased poplar leaves. This study elucidated the fine-tuned regulation of poplar gene expression by BCMV; moreover, the results also suggested that miR156/SPL modules played important roles in the virus response and development of viral systematic symptoms in plant virus disease.

Improving photosynthesis and drought tolerance in Nicotiana tabacum L. by foliar application of salicylic acid

Drought causes a decrease in tobacco yield and quality as well as a reduction in net photosynthetic rate. Salicylic acid (SA) is involved in the regulation of many physiological processes and has been widely used to improve plant drought tolerance. The hydroponic experiment was carried out on flue-cured tobacco variety K326. SA solutions (0.3 mM) were sprayed on the leaves every day for three days, after which 15% PEG-6000 was used to simulate moderate drought. The results showed that drought stress reduced the photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr), while it enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), malondialdehyde (MDA), proline and protein content. Compared with PEG drought stress, SA improved the Pn, Gs and Tr by 45.74%, 26.82%, and 52.22% respectively. Besides, the activities of SOD, POD, CAT, protein and proline content increased by 44.27%, 50.18%, 25%, 34.69% and 24.88%, respectively, while the MDA content decreased by 23.89%. Furthermore, SA spraying increased the drought tolerance of tobacco by modulating the expression level of the genes associated with photosynthesis, carbon metabolism, and photosynthesis-antenna proteins. Hence, SA spraying reduced the inhibition of drought on photosynthesis and stimulated the antioxidant system, thus improving the drought resistance in tobacco.

Studying the effect of light intensity on the photosynthetic mechanism of pepper leaf yellowing mutants by proteomics and phosphoproteomics

The leaf is an important plant organ and is closely related to agricultural yield. Photosynthesis plays a critical role in promoting plant growth and development. Understanding the mechanism of leaf photosynthesis regulation will help improve crop yield. In this study, the pepper yellowing mutant was used as the experimental material, and the photosynthetic changes of pepper leaves (yl1 and 6421) under different light intensities were analyzed by chlorophyll fluorimeter and photosynthesis meter. Changes in proteins and enrichment of phosphopeptides in pepper leaves were determined. The results showed that different light intensities had significant effects on the chlorophyll fluorescence and photosynthetic parameters of pepper leaves. The differentially expressed proteins (DEPs) and differentially expressed phosphorylated proteins (DEPPs) were mainly involved in photosynthesis, photosynthesis-antenna proteins, and carbon fixation in photosynthetic organisms. In yl1 leaves, the phosphorylation levels of photosynthesis and photosynthesis-antenna proteins LHCA2, LHCA3, PsbC, PsbO, and PsbP were lower under low light treatment, but significantly higher under high light intensity compared with wild-type leaves. In addition, many proteins involved in the carbon assimilation pathway, including TKT, Rubisco, and PGK, were phosphorylated, and this modification level was significantly higher in yl1 than in the wild type under high light intensity. These results provide a new perspective for studying the photosynthesis mechanism of pepper under different light intensities.

Leaf Color Classification and Expression Analysis of Photosynthesis-Related Genes in Inbred Lines of Chinese Cabbage Displaying Minor Variations in Dark-Green Leaves.

The leaves of the Chinese cabbage which is most widely consumed come in a wide variety of colors. Leaves that are dark green can promote photosynthesis, effectively improving crop yield, and therefore hold important application and cultivation value. In this study, we selected nine inbred lines of Chinese cabbage displaying slight differences in leaf color, and graded the leaf color using the reflectance spectra. We clarified the differences in gene sequences and the protein structure of ferrochelatase 2 (BrFC2) among the nine inbred lines, and used qRT-PCR to analyze the expression differences of photosynthesis-related genes in inbred lines with minor variations in dark-green leaves. We found expression differences among the inbred lines of Chinese cabbage in photosynthesis-related genes involved in the porphyrin and chlorophyll metabolism, as well as in photosynthesis and photosynthesis-antenna protein pathway. Chlorophyll b content was significantly positively correlated with the expression of PsbQ, LHCA1_1 and LHCB6_1, while chlorophyll a content was significantly negatively correlated with the expression PsbQ, LHCA1_1 and LHCA1_2. Our results provide an empirical basis for the precise identification of candidate genes and a better understanding of the molecular mechanisms responsible for the production of dark-green leaves in Chinese cabbage.

Transcriptome-based analysis of the effects of compound microbial agents on gene expression in wheat roots and leaves under salt stress.

Salt stress inhibits the beneficial effects of most plant growth-promoting rhizobacteria. The synergistic relationship between beneficial rhizosphere microorganisms and plants helps achieve more stable growth-promoting effects. This study aimed 1) to elucidate changes in gene expression profiles in the roots and leaves of wheat after inoculation with compound microbial agents and 2) to determine the mechanisms by which plant growth-promoting rhizobacteria mediate plant responses to microorganisms. Following inoculation with compound bacteria, transcriptome characteristics of gene expression profiles of wheat, roots, and leaves at the flowering stage were investigated using Illumina high-throughput sequencing technology. Gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed on the genes that were significantly differentially expressed. The expression of 231 genes in the roots of bacterial preparations (BIO) -inoculated wheat changed significantly (including 35 upregulated and 196 downregulated genes) compared with that of non-inoculated wheat. The expression of 16,321 genes in leaves changed significantly, including 9651 upregulated genes and 6670 downregulated genes. The differentially expressed genes were involved in the metabolism of carbohydrates, amino acids, and secondary compounds as well as signal transduction pathways. The ethylene receptor 1 gene in wheat leaves was significantly downregulated, and genes related to ethylene-responsive transcription factor were significantly upregulated. GO enrichment analysis showed that metabolic and cellular processes were the main functions affected in the roots and leaves. The main molecular functions altered were binding and catalytic activities, among which the cellular oxidant detoxification enrichment rate was highly expressed in the roots. The expression of peroxisome size regulation was the highest in the leaves. KEGG enrichment analysis showed that linoleic acid metabolism expression was highest in the roots, and the expression of photosynthesis-antenna proteins was the highest in leaves. After inoculation with a complex biosynthesis agent, the phenylalanine ammonia lyase (PAL) gene of the phenylpropanoid biosynthesis pathway was upregulated in wheat leaf cells while 4CL, CCR, and CYP73A were downregulated. Additionally, CYP98A and REF1 genes involved in the flavonoid biosynthesis pathway were upregulated, while F5H, HCT, CCR, E2.1.1.104, and TOGT1-related genes were downregulated. Differentially expressed genes may play key roles in improving salt tolerance in wheat. Compound microbial inoculants promoted the growth of wheat under salt stress and improved disease resistance by regulating the expression of metabolism-related genes in wheat roots and leaves and activating immune pathway-related genes.

Heterologous expression of Zygophyllum xanthoxylon zinc finger protein gene (ZxZF) enhances the tolerance of poplar photosynthetic function to drought stress

The ZxZF transcription factor (TF) of Zygophyllum xanthoxylon (Bunge) Maxim, an extremely drought-resistant woody plant, is a C2H2 zinc finger protein. Studies have shown that C2H2 zinc finger proteins play important roles in activating stress-related genes and enhancing plant resistance. However, their function in regulating plant photosynthesis under drought stress is not well understood. Since poplar is an important greening and afforestation tree species, it is particularly important to cultivate excellent drought-tolerant varieties. The ZxZF transcription factor (TF) was heterogeneously expressed in Euroamerican poplar (Populus × euroameracana cl.'Bofengl’) by genetic transformation. Based on the mechanism and potential function of poplar photosynthesis regulated by ZxZF under drought stress, transcriptomic and physiological determinations were used to reveal the important role of this gene in improving the drought resistance of poplar. The results showed that the overexpression of ZxZF TF in transgenic poplars could improve the inhibition of Calvin cycle by regulating stomatal opening and increasing the concentration of intercellular CO2. The chlorophyll content, photosynthetic performance index, and photochemical efficiency of transgenic lines under drought stress were significantly higher than those of the wild type (WT). The overexpression of ZxZF TFs could alleviate the degree of photoinhibition of photosystems II and I under drought stress and maintain the efficiency of light energy capture and the photosynthetic electron transport chain. The transcriptomic data also showed that differentially expressed genes between the transgenic poplar and WT under drought stress were primarily enriched in metabolic pathways related to photosynthesis, such as photosynthesis, photosynthesis-antenna protein, porphyrin and chlorophyll metabolism, and photosynthetic carbon fixation, and the downregulation of genes related to chlorophyll synthesis, photosynthetic electron transport and Calvin cycle were alleviated. In addition, the overexpression of ZxZF TF can alleviate the inhibition of NADH dehydrogenase-like (NDH) cyclic electron flow of the poplar NDH pathway under drought stress, which plays an important role in reducing the excess pressure of electrons on the photosynthetic electron transport chain and maintaining the normal photosynthetic electron transport. In summary, the overexpression of ZxZF TFs can effectively alleviate the inhibition of drought on the assimilation of carbon in poplar and have a positive impact on light energy capture, the orderly transport of photosynthetic electron transport chain and the integrity of the photosystem, which is highly significant to acheivean in-depth understanding of the function of ZxZF TFs. This also provides an important basis for the breeding of new transgenic poplar varieties.

Transcriptomics Combined with Photosynthetic Physiology and Leaf Structure Analysis Revealed Increased Sugarcane Yield by Fenlong-Ridging

Fenlong-ridging (FL) is a new type of conservation tillage. In many crops, FL increases crop yield and quality; however, the cytology and molecular mechanisms of crops under FL is not completely understood. This study investigated soil physical and chemical properties under FL and conventional tillage (CK) during 2018–2019 (plant cane) and 2019–2022 (first stubble), and analyzed the agronomic trait, physiology, leaf anatomical structure, and gene expression related to photosynthesis between FL and CK of sugarcane (Guitang 42). Soil bulk density significantly increased, and soil porosity, water storage, and content of available nitrogen and phosphorus under FL were significantly higher than those under CK. Plant height, stem diameter, single stem weight, effective stem number and yield significantly increased under FL compared to under CK. Sugar content significantly increased in plant cane under FL. Chlorophyll content and the photosynthetic rate increased, with significantly higher activity of photosynthetic enzymes including NADP-malate dehydrogenase (NADP-MDH), phosphoenolpyruvate carboxylase (PEPC), and ribulose-1,5-bisphosphate carboxylase (RuBPC) under FL compared to CK. Fenlong-ridging cytology results showed that the mesophyll cells were large and arranged well, the Kranz anatomy was noticeable, and there were a high number of large chloroplasts in mesophyll cell and in the vascular bundle sheath. Furthermore, the bundle sheath in FL was larger than that in CK. Transcriptomics results showed that 19,357 differentially genes (DEGs) were up-regulated and 28,349 DEGs were down-regulated in sugarcane leaves under FL vs. CK. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that abundant DEGs were enriched in photosynthesis, photosynthesis-antenna protein, carotenoid biosynthesis, and other pathways associated with photosynthesis. Most expression was up-regulated, thus, facilitating photosynthesis regulation. Quantitative real-time polymerase chain reaction analysis revealed the up-regulation of genes related to photosynthesis (PsaH and PsbS) under FL. Overall, this study provides insights into the role of FL in increased sugarcane yield by integrating physiology, cytology, and proteomics analysis. These findings could be used to further improve its application and promotion.

Low nitrogen stress-induced transcriptome changes revealed the molecular response and tolerance characteristics in maintaining the C/N balance of sugar beet (Beta vulgaris L.).

Nitrogen (N) is an essential macronutrient for plants, acting as a common limiting factor for crop yield. The application of nitrogen fertilizer is related to the sustainable development of both crops and the environment. To further explore the molecular response of sugar beet under low nitrogen (LN) supply, transcriptome analysis was performed on the LN-tolerant germplasm '780016B/12 superior'. In total, 580 differentially expressed genes (DEGs) were identified in leaves, and 1,075 DEGs were identified in roots (log2 |FC| ≥ 1; q value < 0.05). Gene Ontology (GO), protein-protein interaction (PPI), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses clarified the role and relationship of DEGs under LN stress. Most of the downregulated DEGs were closely related to "photosynthesis" and the metabolism of "photosynthesis-antenna proteins", "carbon", "nitrogen", and "glutathione", while the upregulated DEGs were involved in flavonoid and phenylalanine biosynthesis. For example, GLUDB (glutamate dehydrogenase B) was identified as a key downregulated gene, linking carbon, nitrogen, and glutamate metabolism. Thus, low nitrogen-tolerant sugar beet reduced energy expenditure mainly by reducing the synthesis of energy-consuming amino acids, which in turn improved tolerance to low nitrogen stress. The glutathione metabolism biosynthesis pathway was promoted to quench reactive oxygen species (ROS) and protect cells from oxidative damage. The expression levels of nitrogen assimilation and amino acid transport genes, such as NRT2.5 (high-affinity nitrate transporter), NR (nitrate reductase [NADH]), NIR (ferredoxin-nitrite reductase), GS (glutamine synthetase leaf isozyme), GLUDB, GST (glutathione transferase) and GGT3 (glutathione hydrolase 3) at low nitrogen levels play a decisive role in nitrogen utilization and may affect the conversion of the carbon skeleton. DFRA (dihydroflavonol 4-reductase) in roots was negatively correlated with NIR in leaves (coefficient = -0.98, p < 0.05), suggesting that there may be corresponding remote regulation between "flavonoid biosynthesis" and "nitrogen metabolism" in roots and leaves. FBP (fructose 1,6-bisphosphatase) and PGK (phosphoglycerate kinase) were significantly positively correlated (p < 0.001) with Ci (intercellular CO2 concentration). The reliability and reproducibility of the RNA-seq data were further confirmed by real-time fluorescence quantitative PCR (qRT-PCR) validation of 22 genes (R2 = 0.98). This study reveals possible pivotal genes and metabolic pathways for sugar beet adaptation to nitrogen-deficient environments.

Proteomic, transcriptomic, biochemical, and physio-anatomical analyses provide insights into energy metabolism, light usage, and photosynthesis in cigar tobacco under different light intensities

Low light (LL) resulting in shading are among the detrimental abiotic stresses limiting plant growth and suppressing crop productivity. Shading is a key cultivation technique in cigar wrapper tobacco production but little is known about its impact on transcriptional and translational regulatory networks. Here, we integrate transcriptomic and proteomic profiling with physio-biochemical and anatomical analyses under different light intensities [T200 (200 μmol m−2 s−1), T100 (100 μmol m−2 s−1), and T50 (50 μmol m−2 s−1)] to uncover the underlying molecular response mechanisms of tobacco plants. We found that the leaf anatomical structure impacts photosynthetic capacity and that LL intensities (particularly T50) decrease leaf and palisade thickness (42%) and spongy tissues (16%), which leads to a lower photosynthetic rate (84%) compared with T200. Furthermore, we identified 3045 and 590 significantly differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) in the transcriptome and proteome of cigar tobacco, respectively. A total of 110 pairs were correlated which were upregulated in photosynthesis-antenna proteins, photosynthesis, and defense/detoxification-related pathways, according to integrated omics analyses, and downregulated in tyrosine metabolism, starch and sucrose metabolism, mitochondrial electron transport chain, and glycolysis pathways; and associated with decreased activities of glyceraldehyde-3-phosphate dehydrogenase (31%), starch phosphorylase (25%), and pyruvate kinase (24%) enzymes related to glycolysis. Our results show that cigar tobacco efficiently utilizes low light to reconfigure its energy metabolism, and offer profound insights into the response mechanisms at the physio-biochemical, anatomical, and molecular levels. This study thus represents a valuable resource of genes and proteins for future functional studies underlying LL response.

Integrative Analysis of Transcriptome, Proteome, and Phosphoproteome Reveals Potential Roles of Photosynthesis Antenna Proteins in Response to Brassinosteroids Signaling in Maize.

Brassinosteroids are a recently discovered group of substances that promote plant growth and productivity. Photosynthesis, which is vital for plant growth and high productivity, is strongly influenced by brassinosteroid signaling. However, the molecular mechanism underlying the photosynthetic response to brassinosteroid signaling in maize remains obscure. Here, we performed integrated transcriptome, proteome, and phosphoproteomic analyses to identify the key photosynthesis pathway that responds to brassinosteroid signaling. Transcriptome analysis suggested that photosynthesis antenna proteins and carotenoid biosynthesis, plant hormone signal transduction, and MAPK signaling in CK VS EBR and CK VS Brz were significantly enriched in the list of differentially expressed genes upon brassinosteroids treatment. Consistently, proteome and phosphoproteomic analyses indicated that photosynthesis antenna and photosynthesis proteins were significantly enriched in the list of differentially expressed proteins. Thus, transcriptome, proteome, and phosphoproteome analyses showed that major genes and proteins related to photosynthesis antenna proteins were upregulated by brassinosteroids treatment in a dose-dependent manner. Meanwhile, 42 and 186 transcription factor (TF) responses to brassinosteroid signals in maize leaves were identified in the CK VS EBR and CK VS Brz groups, respectively. Our study provides valuable information for a better understanding of the molecular mechanism underlying the photosynthetic response to brassinosteroid signaling in maize.

Silencing of Pepper CaFtsH1 or CaFtsH8 Genes Alters Normal Leaf Development.

Filamentation temperature-sensitive H (FtsH) is a proteolytic enzyme that plays an important role in plant photomorphogenesis and stress resistance. However, information regarding the FtsH family genes in pepper is limited. In our research, through genome-wide identification, 18 members of the pepper FtsH family (including five FtsHi members) were identified and renamed based on phylogenetic analysis. CaFtsH1 and CaFtsH8 were found to be essential for pepper chloroplast development and photosynthesis because FtsH5 and FtsH2 were lost in Solanaceae diploids. We found that the CaFtsH1 and CaFtsH8 proteins were located in the chloroplasts and specifically expressed in pepper green tissues. Meanwhile, CaFtsH1 and CaFtsH8-silenced plants created by virus-induced gene silencing exhibited albino leaf phenotypes. In addition, CaFtsH1-silenced plants were observed to contain very few dysplastic chloroplasts and lost the capacity for photoautotrophic growth. Transcriptome analysis revealed that the expression of chloroplast-related genes such as those coding the photosynthesis-antenna protein and structural proteins was downregulated in CaFtsH1-silenced plants, resulting in the inability to form normal chloroplasts. This study improves our understanding of pepper chloroplast formation and photosynthesis through the identification and functional study of CaFtsH genes.

Transcriptome sequencing analysis revealing the potential mechanism of seed germination in Pulsatilla chinensis (Bunge) Regel

AbstractPulsatilla chinensis (Bunge) Regel has been widely used in the pharmaceutical industry. With the deepening of clinical application, the research on its plant resources has attracted much attention. However, the underlying molecular mechanisms of distinct germination during Pulsatilla seed development are still mostly unknown. Therefore, in this study, four germination stages of P. chinensis seeds, with obvious differences in seed appearance traits, were used as materials. Transcriptome sequencing technology was used to analyse the molecular mechanisms of seed germination. A total of 27,601 differentially expressed genes (DEGs) (six different groups) were determined. KEGG enrichment analysis revealed that the up-regulated DEGs were enriched in phenylpropanoid biosynthesis, photosynthesis, photosynthesis–antenna proteins, plant hormone signal transduction, flavonoid biosynthesis and other pathways. A total of 87 DEGs was enriched in phytohormone signal transduction pathways, including auxin (25), abscisic acid (13), gibberellin (6), ethylene (9) and cytokinin (7). Furthermore, a protein–protein interaction network was constructed using these DEGs. Some DEGs were validated by qRT-PCR analysis. This comprehensive analysis provided basic information on the key genes of plant hormone signal transduction pathways involved in the seed germination process of P. chinensis (Bunge) Regel.