Low Temperature Stress Research Articles

Genome-wide identification and expression analysis of two-component system genes in switchgrass (Panicum virgatum L.)

The two-component system (TCS) consists of histidine kinase (HK), histidine phosphate transfer protein (HP), and response regulatory factor (RR). It is one of the most crucial components of signal transduction in plants, playing a significant role in regulating plant growth, development, and responses to various abiotic stresses. Although TCS genes have been extensively identified in a variety of plants, the genome-wide recognition and examination of TCS in switchgrass remain unreported. Accordingly, this study identified a total of 87 TCS members in the genome of switchgrass, comprising 20 HK(L)s, 10 HPs, and 57 RRs. Detailed analyses were also conducted on their gene structures, conserved domains, and phylogenetic relationships. Moreover, this study analysed the gene expression profiles across diverse organs and investigated their response patterns to adverse environmental stresses. Results revealed that 87 TCS genes were distributed across 18 chromosomes, with uneven distribution. Expansion of these genes in switchgrass was achieved through both fragment and tandem duplication. PvTCS members are relatively conservative in the evolutionary process, but the gene structure varies significantly. Various cis-acting elements, varying in types and amounts, are present in the promoter region of PvTCSs, all related to plant growth, development, and abiotic stress, due to the TCS gene structure. Protein-protein interaction and microRNA prediction suggest complex interactions and transcriptional regulation among TCS members. Additionally, most TCS members are expressed in roots and stems, with some genes showing organ-specific expression at different stages of leaf and inflorescence development. Under conditions of abiotic stress such as drought, low temperature, high temperature, and salt stress, as well as exogenous abscisic acid (ABA), the expression of most TCS genes is either stimulated or inhibited. Our systematic analysis could offer insight into the characterization of the TCS genes, and further the growth of functional studies in switchgrass.

Improving Process-Based Modelling to Simulate the Effects of Low-Temperature Stress During Pre-Anthesis on the Quality Characteristics of Wheat Grains.

Low temperatures in late spring pose a potential threat to the maintenance of grain yield and quality. Despite the importance of protein and starch in wheat quality, they are often overlooked in models addressing climate change effects. In this study, we conducted multiyear environment-controlled phytotron experiments and observed adverse effects resulting from low-temperature stress (LTS) on plant carbon and nitrogen dynamics, grain protein and starch formation, and sink capacity. We quantified the relationships between low temperature during the jointing and booting stages and plant nitrogen uptake, grain nitrogen accumulation, grain starch accumulation, grain setting, and potential grain weight using source-sink relationship-based methods. The LTS factor was introduced to account for the cultivar-specific to LTS at different growth stages. Compared with the original model, the improved model produced fewer errors when simulating aboveground nitrogen accumulation, grain protein concentration, grain starch concentration, grain starch yield, grain number, and grain weight under LTS, with reductions of 60%, 71%, 73%, 58%, 50% and 65%, respectively. The improvements in the model enhance its mechanism and applicability in assessing short-term successive frost effects on wheat grain quality. Furthermore, when using the improved model, special attention should be given to the low-temperature sensitivity parameters.

Spraying KH2PO4 Alleviates the Damage of Spring Low-Temperature Stress by Improving the Physiological Characteristics of Wheat Flag Leaves

The low-temperature stress (LTS) in spring results in tremendous yield loss in wheat production, and the application of potassium dihydrogen phosphate (KH2PO4) can alleviate stress-induced damage. However, the underlying effect of spraying KH2PO4 on the physiological characteristics of wheat flag leaves under spring LTS remains unclear. In this study, we investigated the effect of spraying KH2PO4 on flag leaf physiological traits and yield under spring LTS, including treatments at 15 °C and spraying H2O (CK), treatment at −4 °C and spraying H2O (LT1), and treatment at −4 °C and spraying KH2PO4 (LT2). The results showed that spraying KH2PO4 significantly increased the activities of the superoxide dismutase (SOD), the peroxidase (POD), and the catalase (CAT), and reduced malondialdehyde (MDA) content in the flag leaves. Compared to LT1, the SOD, POD, and CAT activities in the flag leaves of the Yangnong19 (YN19) and Xinmai26 (XM26) via LT2 increased by 5.5%, 10.9%, and 3.9%, and 5.4%, 9.2%, and 4.4%, respectively, and the MDA content of the YN19 and XM26 decreased by 10.5% and 9.1%, respectively, at 0–12 d after low temperature treatment (DALTT). Spraying KH2PO4 appreciably alleviated damage to the leaf cell morphology and tissue integrity, and increased the accumulation of proline and soluble protein, the chlorophyll content, and the activities of Ribulose–1,5–bisphosphate carboxylase and phosphoenolpyruvate carboxykinase. The net photosynthetic rate in the flag leaves of the YN19 and XM26 via LT2 increased by 37.9% and 35.9%, respectively, at 0–12 DALTT, compared to LT1. Moreover, spraying KH2PO4 reduced the yield loss rate of the YN19 and XM26 by 13.06% and 16.72%, respectively. The present study demonstrates that spraying KH2PO4 can enhance wheat resistance to spring LTS and maintain the photosynthetic capacity of flag leaves, alleviating the negative effects of LTS on grain yield.

Enhancing cold tolerance in tobacco through endophytic symbiosis with Piriformospora indica

Tobacco, a warm-season crop originating from the Americas, is highly susceptible to cold stress. The utilization of symbiotic fungi as a means to bolster crops’ resilience against abiotic stresses has been proven to be a potent strategy. In this study, we investigated the effect of endophytic fungus Piriformospora indica on the cold resistance of tobacco. When exposed to cold stress, the colonization of P.indica in tobacco roots effectively stimulates the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). This, in turn, reduces the accumulation of reactive oxygen species (ROS), thereby mitigating oxidative damage. Additionally, P. indica elevates the levels of osmolytes, such as soluble sugars, proline, and soluble proteins, thus facilitating the restoration of osmotic balance. Under cold stress conditions, P. indica also induces the expression of cold-responsive genes. Furthermore, this fungus not only enhances photosynthesis in tobacco by stimulating the synthesis of photosynthetic pigments, strengthening Rubisco activity, and elevating PSII efficiency, but also fortifies tobacco’s nitrogen assimilation by inducing the expression of nitrate transporter gene and activating enzymes related to nitrogen assimilation. Consequently, this synergistic optimization of nitrogen and carbon assimilation provides a solid material and energetic foundation for tobacco plants to withstand cold stress. Our study demonstrates that a mycorrhizal association between P. indica and tobacco seedlings provides multifaceted protection to tobacco plants against low-temperature stress and offers a valuable insight into how P. indica enhances the cold tolerance of tobacco.

Optimized Phosphorus Application Enhances Wheat Stem Lodging Resistance Under Spring Low-Temperature Stress

Spring low-temperature stress (LTS) has become a major limiting factor for the development of high yield, quality and efficiency in wheat production. It not only affects the function of wheat leaves and the development of spikes but also impacts stem lodging resistance, and may experience elevated risk of stem lodging. This study conducted a field pot experiment to assess the effect of phosphorus fertilizer application mode on wheat stem lodging resistance under spring LTS. Two wheat varieties, Yannong19 (YN19, cold-tolerant variety) and Xinmai26 (XM26, cold-sensitive variety) used as the experiment material. Two phosphorus fertilizer application models including traditional phosphorus application (TPA) and optimized phosphorus application (OPA) were employed. Temperature treatment was conducted at 15 °C (CK) and −4 °C (LT) in a controlled phytotron. Our results showed that spring LTS decreased the stem wall thickness and internode fullness, and altered stem anatomical structure and chemical composition, resulting in a decrease in wheat stem mechanical strength and lodging resistant index. Compared with TPA, the OPA increased the stem wall thickness and internode fullness. The thickness of the stem mechanic tissue layer and parenchymatous tissue, and the area of the large vascular bundle and small vascular bundle were increased by the OPA, which alleviated the damage to stem cell walls caused by spring LTS. At the same time, the OPA also increased the contents of lignin, cellulose, and soluble sugar, improving the C/N ratio in wheat stem. Due to the improved stem morphological characteristics, anatomical structure, and chemical compositions, the wheat stem exhibited enhanced lodging resistance, which increased the lodging resistant index of the 2nd and 3rd internodes of YN19 and XM26 by 27.27%, 11.63% and 14.15%, 15.73% at the dough stage compared with TPA under spring LTS. Meanwhile, OPA could not only alleviate the yield loss caused by spring LTS, but also increase the grain yield without spring LTS. This study indicated that OPA enhances wheat stem lodging resistance under spring LTS, and would be meaningful and practical for improving wheat resistance to low-temperature stress.

Identification of AP2/ERF Transcription Factors and Characterization of AP2/ERF Genes Related to Low-Temperature Stress Response and Fruit Development in Luffa

Plant-specific APETALA2/Ethylene-Responsive Factor (AP2/ERF) transcription factors are involved in the regulation of genes associated with the growth and developmental processes of numerous plants. Although AP2/ERF proteins from other species have been intensively studied, no studies have been reported on the AP2/ERF family of Luffa cylindrica, an important vegetable of the cucurbit family, and one of the most popular vegetables in the world. In this study, 133 genes (315–6696 bp) encoding LcAP2/ERF proteins with complete AP2/ERF domains were identified according to the luffa P93075 genome. These LcAP2/ERF genes were subsequently classified and analyzed for their gene structures, chromosomal distribution locations, promoter cis-acting elements, conserved structural domains of encoded proteins, and responses to abiotic stresses. The LcAP2/ERF genes were identified and divided into five phylogenetic groups (AP2, DREBs, ERFs, RAV, and soloists). These genes were unevenly distributed across 13 chromosomes. An analysis of gene structures indicated the LcAP2/ERF genes contained 0–11 introns (average of 4.4). Additionally, 16 motifs were identified in the LcAP2/ERF proteins that were conserved across different phylogenetic groups. Moreover, 11 cis-acting elements associated with response to the environment were analyzed in a 2000 bp region upstream of the LcAP2/ERF gene promoters. A transcriptome analysis involving RNA-seq data revealed tissue-specific LcAP2/ERF expression profiles and the diversity in LcAP2/ERF expression. The effects of low-temperature stress on LcAP2/ERF expression were determined. Furthermore, fruit-development-related and low-temperature-induced expressional changes were verified by RT-qPCR analyses of 14 differentially expressed LcAP2/ERF genes in luffa. Our findings will help clarify the evolution of the luffa AP2/ERF family, while also providing valuable insights for future studies on AP2/ERF functions.

Identification of quinoa B3 gene family and its expression pattern in response to low temperature stress

Identification of quinoa B3 gene family and its expression pattern in response to low temperature stress

Response of Different Exogenous Phytohormones to Rice Yield Under Low-Temperature Stress at the Filling Stage

This paper aims to clarify the effects of different exogenous phytohormones on the physiological traits of rice (Oryza sativa L.) at the early stage of irrigation under low-temperature stress. In this study, two types of rice varieties with different temperature sensitivities screened out previously, namely, a cold-tolerant variety (Nan Jing 9108) and a low-temperature-sensitive variety (Hui Liang You 898), were used in pots to simulate the process of low-temperature stress in rice at the early stage of grouting (6–9 days after anthesis) with artificial low-temperature treatments. The experimental treatments were 450 mg L−1 Methyl jasmine acid (MJ), 46 mg L−1 Melatonin (MT), 69 mg L−1 Salicylate (SA), 40 mg L−1 Erythromycin (GA3), 25 mg L−1 Zeatin (Z), 145 mg L−1 Spermidine (SPD), and 5 mg L−1 Abscisic acid (ABA) sprayed on rice before low-temperature stress, while low-temperature treatment without spraying (DK) and conventional planting without spraying (CK) were added as the control. The results showed that compared with the room temperature control (CK, sprayed with deionized water), the low-temperature control (DK, low-temperature treatment, and sprayed with deionized water) all significantly reduced the rice grain yield. Different exogenous hormones sprayed before low-temperature stress could increase rice yield, among which, Z and SPD spraying treatments had a better effect on the yield of Hui Liang You 898, while different exogenous hormone treatments increased the yield of Nan Jing 9108 in an average manner. The Z and SPD treatments increased the yield of Hui Liang You 898 by 24.87% and 26.16% and that of Nan Jing 9108 by 15.87% and 17.80%, respectively. This was mainly attributed to the significant increase in thousand-grain weight and fruiting rate, while there was no significant difference in the number of spikes and number of grains. The different exogenous hormone treatments were able to delay leaf senescence, enhance the photosynthetic production capacity of plants by increasing leaf chlorophyll content, and thus increase the accumulation of photosynthetic assimilation products and population growth rate after flowering. Among them, both Z and SPD treatments resulted in a population growth rate of more than 30% from spike flushing to maturity, which led to a higher dry matter accumulation of the plant at maturity. In addition, in the dry matter distribution of the plant at maturity, the seeds occupied a higher accumulation amount and proportion compared with the respective DK; the SPD treatment resulted in the maximum distribution rate of seeds at maturity of Hui Liang You 898, with an increase of 8.27%, and the Z treatment resulted in the maximum distribution rate of seeds at maturity of Nan Jing 9108, with an increase of 7.34%. At the same time, the Z treatment significantly increased the activities of adenosine diphosphate glucose phosphorylated enzyme (AGP) and starch branching enzyme (SBE) in the grains of both varieties, which resulted in the accumulation of more starch and ultimately increased the rice grain yield. The results verified that different exogenous phytohormones could be used to regulate the insufficiency of grouting caused by low-temperature stress during the grouting and fruiting stages of rice and enriched their agronomic and physiological traits in response at the same time.

Genome-Wide Identification of the Cyclic Nucleotide-Gated Ion Channel Gene Family and Expression Profiles Under Low-Temperature Stress in Luffa cylindrica L.

Cyclic nucleotide-gated ion channels (CNGCs) are cell membrane channel proteins for calcium ions. They have been reported to play important roles in survival and in the responses to environmental factors in various plants. However, little is known about the CNGC family and its functions in luffa (Luffa cylindrica L.). In this study, a bioinformatics-based method was used to identify members of the CNGC gene family in L. cylindrica. In total, 20 LcCNGCs were detected, and they were grouped into five subfamilies (I, II, Ⅲ, IV-a, and IV-b) in a phylogenetic analysis with CNGCs from Arabidopsis thaliana (20 AtCNGCs) and Momordica charantia (17 McCNGCs). The 20 LcCNGC genes were unevenly distributed on 11 of the 13 chromosomes in luffa, with none on Chromosomes 1 and 5. The members of each subfamily encoded proteins with highly conserved functional domains. An evolutionary analysis of CNGCs in luffa revealed three gene losses and a motif deletion. An examination of gene replication events during evolution indicated that two tandemly duplicated gene pairs were the primary driving force behind the evolution of the LcCNGC gene family. PlantCARE analyses of the LcCNGC promoter regions revealed various cis-regulatory elements, including those responsive to plant hormones (abscisic acid, methyl jasmonate, and salicylic acid) and abiotic stresses (light, drought, and low temperature). The presence of these cis-acting elements suggested that the encoded CNGC proteins may be involved in stress responses, as well as growth and development. Transcriptome sequencing (RNA-seq) analyses revealed tissue-specific expression patterns of LcCNGCs in various plant parts (roots, stems, leaves, flowers, and fruit) and the upregulation of some LcCNGCs under low-temperature stress. To confirm the accuracy of the RNA-seq data, 10 cold-responsive LcCNGC genes were selected for verification by quantitative real-time polymerase chain reaction (RT-qPCR) analysis. Under cold conditions, LcCNGC4 was highly upregulated (>50-fold increase in its transcript levels), and LcCNGC3, LcCNGC6, and LcCNGC13 were upregulated approximately 10-fold. Our findings provide new information about the evolution of the CNGC family in L. cylindrica and provide insights into the functions of the encoded CNGC proteins.

Exploring Functional Gene XsPDAT1’s Involvement in Xanthoceras sorbifolium Oil Synthesis and Its Acclimation to Cold Stress

Phospholipid: diacylglycerol acyltransferase (PDAT) is crucial in triacylglycerol (TAG) synthesis as it represents the final rate-limiting step of the acyl-CoA-independent acylation reaction. PDAT not only regulates lipid synthesis in plants, but also plays an important function in improving stress tolerance. In this study, the full-length coding sequence (CDS) of XsPDAT1, totaling 2022 base pairs and encoding 673 amino acids, was cloned from Xanthoceras sorbifolium. The relative expression of XsPDAT1 was significantly and positively correlated with oil accumulation during seed kernel development; there were some differences in the expression patterns under different abiotic stresses. Transgenic Arabidopsis thaliana plants overexpressing XsPDAT1 were obtained using the Agrobacterium-mediated method. Under low-temperature stress, the transgenic plants exhibited a smaller decrease in chlorophyll content, a smaller increase in relative conductivity, and a larger increase in POD enzyme activity and proline content in the leaves compared with the wild type. Additionally, lipid composition analysis revealed a significant increase in unsaturated fatty acids, such as oleic (C18:1) and linoleic (C18:2), in the seeds of transgenic plants compared to the wild type. These results suggest that XsPDAT1 plays a dual role in regulating the ratio of fatty acid composition and low-temperature stress in plants.

Genome-wide identification of Aux/IAA gene family members in grape and functional analysis of VaIAA3 in response to cold stress.

Twenty-five VvIAA genes and eighteen VaIAA genes were identified from Pinot Noir and Shanputao, respectively. The overexpression of VaIAA3 in transgenic Arabidopsis increased cold tolerance by regulating auxin, ABA and ethylene signaling. Aux/IAA genes are key genes involved in regulating auxin signal transduction in plants. Although IAA genes have been characterized in various plant species, the role of IAA genes in grape cold resistance is unclear. To further explore the members of the Aux/IAA gene family in grape and their functions, in this study, using genomic data for Pinot Noir (Vitis vinifera cv. 'Pinot Noir') and Shanputao (Vitis amurensis), 25 VvIAA genes and 18 VaIAA genes were identified. The VaIAA genes presented different expression patterns at five different temperatures (28 ± 1 °C, 5 ± 1 °C, 0 ± 1 °C, -5 ± 1 °C, and -10 ± 1 °C) according to qRT‑PCR results. VaIAA3 was selected as a candidate gene for further functional analysis because of its high expression level under low-temperature stress. Subcellular localization experiments revealed that VaIAA3 was localized in the nucleus. Additionally, under 4 °C treatment for 24 h, relative expression level of VaIAA3, antioxidant enzyme activity, survival rate, and cold-responsive gene expression in three transgenic lines (OE-1, OE-2, OE-3) were greater, whereas relative electrolytic conductivity (REC), malondialdehyde (MDA) content and hydrogen peroxide (H2O2) content were lower than those of the wild type (WT). Transcriptome sequencing analysis revealed that VaIAA3 regulated cold stress resistance in Arabidopsis thaliana (Arabidopsis) through pathways involving auxin, ABA, JA, or ethylene. Importantly, heterologous overexpression of VaIAA3 increased the resistance of Arabidopsis to cold stress, which provides a theoretical basis for the further use of VaIAA3 to improve cold resistance in grape.

Genome-wide identification, expression analysis of the R2R3-MYB gene family and their potential roles under cold stress in Prunus sibirica

BackgroundThe R2R3-MYB transcription factors in plants participate in various physiological and biochemical processes and responds to various external stimuli. Prunus sibirica (known as Siberian apricot) is a drupe tree species that produces extremely high nutritional value kernels. However, it is susceptiblility to frost damage during the flowering period, results in a marked reduction in kernel yield.ResultsIn this study, the MYB gene family of P. sibirica (PsMYB) was systematically analyzed, and 116 R2R3-MYB genes that were distributed unevenly over eight chromosomes were ultimately screened. Phylogenetic analysis divided these 116 genes into 30 subgroups. We discovered that 37 PsMYBs had cold stress-responsive promoters, and six PsMYBs were annotated to be associated with cold response. Intraspecific homology analysis identified segmental duplication as the primary gene amplification mechanism, and homology analysis of the PsMYB genes with those of five other species revealed phylogenetic relationships with Rosaceae species. Protein interaction studies revealed collaborative regulation of the PsMYB proteins with Arabidopsis protein, and transcriptome analysis identified PsMYB genes that were highly expressed at low temperatures. Additionally, the expression levels of 22 PsMYBs in different tissue parts of P. sibirica and under different low-temperature stress conditions were evaluated using quantitative real-time PCR, with the results verifying that PsMYBs are specifically expressed in different plant parts and may be involved in the growth and development of P. sibirica species. Genes upregulated after exposure to low-temperature stress and likely involved in cold response were identified.ConclusionThis study lays a foundation for understanding the molecular biology of PsMYBs in P. sibirica and provides a theoretical basis for the future study of transgenic lines with cold resistance during the flowering period of this tree.

Effects of Pollen Germination and Pollen Tube Growth under Different Temperature Stresses in Mango (Mangifera indica L.) by Metabolome.

The dramatic temperature fluctuations spurred by global warming and the accompanying extreme weather events inhibit mango growth and threaten mango productivity. Particularly, mango flowering is highly sensitive to temperature changes. The mango fruit setting rate was significantly positively correlated with pollen activity, and pollen activity was regulated by different metabolites. In this study, the in vitro pollen of two mango varieties ('Renong No.1' and 'Jinhuang'), in which sensitivity to temperature differed significantly, were subjected to different temperature stresses (15 °C, 25 °C and 35 °C), and their metabolomics were analyzed. The present results showed that 775 differential metabolites were screened by liquid chromatography-mass spectrometry and divided into 12 categories. The two varieties had significant differences in metabolite expression under different temperature stresses and the effect of low temperature on 'Renong No.1' mainly focused on amino acid metabolism, while the effect on 'Jinhuang' was mainly related to glycolysis. However, under the 35 °C temperature stress, 'Renong No.1' responded by redistributing riboflavin and betaine in vivo and the most obvious metabolic pathway of 'Jinhuang' enrichment was pyrimidine metabolism, which had undergone complex main body formation and extensive regulatory processes. The changes of metabolites of different varieties under low temperature and high temperature stress were different. Among them, flavonoids or flavonoid derivatives were included in class A (216 metabolites), C (163 metabolites) and D (233 metabolites) metabolites, indicating that flavonoid metabolites had an obvious regulatory effect on mango pollen metabolism under different temperature stress. The present results provide valuable information for reproductive biology studies and breeding in mango, in particular, the selection and breeding of the most suitable varieties for different production areas.

Effects of temperature and drought stress on the seed germination of a peatland lily (Lilium concolor var. megalanthum).

Sexual reproduction through seeds is an effective way to renew plant populations and increase their genetic diversity, but seed germination process is complicated and relatively difficult due to the restriction of environmental conditions. Wetland plants that reproduce sexually through seeds may be affected by changes in moisture and temperature. This study aims to explore the ecological adaptation strategies of seed germination of Lilium concolor var. megalanthum under different hydrothermal conditions. Controlled experiments were conducted to investigate the germination performance of L. concolor var. megalanthum seeds at different temperatures (10°C, 15°C, 20°C, 25°C, and 30°C) and simulated drought stress conditions using PEG-6000 solutions (0%, 5%, 10%, 15%, and 20%). The results showed that temperature, drought stress, and their interaction significantly affected the days to first germination, germination percentage, coefficient of germination rate, germination energy, germination index, and vigor index of seeds (p<0.01). The germination percentage, germination index, and vigor index of seed were significantly higher at 25°C compared to other temperatures (p<0.01). The interaction between low temperature and drought stress significantly delayed the days to first germination. The inhibition of drought stress on seed germination was enhanced by PEG-6000 solution under high temperature. Under the conditions of 25°C and 5% PEG-6000 solution concentration, seeds of L. concolor var. megalanthum exhibited optimal germination parameters. At 10°C and 15°C, the seeds exhibited the highest tolerance to PEG-6000-simulated drought stress. Rehydration germination results showed that extreme temperatures and drought stress conditions inhibit seed germination of L. concolor var. megalanthum without damaging seed structure. The germination pattern of seeds under variable temperature and drought stress conditions reflects their adaptive strategies developed over long-term evolution to cope with the environmental conditions.

Effects of exogenous calcium and calcium inhibitor on physiological characteristics of winter turnip rape (Brassica rapa) under low temperature stress

Low temperature is one of the environmental factors that restrict the growth and geographical distribution of Brassica. To investigate the effects of exogenous calcium and calcium inhibitor on the ability of winter turnip rapeseed (Brassica rapa L.) to withstand low temperatures (4℃), we used a strong cold-resistant variety Longyou 7 (L7) and a weak cold-resistant variety Longyou 99 (L99) as the materials. The seedlings were treated with CaCl2 (20 mmol·L-1) and calcium inhibitor LaCl3 (10 mmol·L-1) at 0 h (CK), 6 h, 12 h, 24 h and 48 h after 4℃ treatments. Physiological characteristics, Ca2+ flux and Ca2+ concentration in roots after treatments were analyzed. Results illustrated that under 4℃ treatment, activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased by both CK and exogenous CaCl2 treatments. Contents of soluble protein (SP) and proline (Pro) increased, while contents of malondialdehyde (MDA) decreased, resulting in reduced membrane lipid peroxidation. But enzyme activity decreased and MDA content increased following treatment with exogenous LaCl3. The rate of Ca2+ flow showed a higher uptake in L7 roots compared with L99. L99 showed Ca2+ efflux with a rate of 30.21 pmol‧cm-2‧s-1, whereas L7 showed short efflux then returned to influx. Calcium ion content in roots decreased in both cultivars after CaCl2 treatment. Results of RNA-seq revealed that genes were differentially expressed in response to low temperatures, hormones, photosystem II, chloroplasts, DNA replication, ribosomal RNA processing, and translation. This study found significant expression genes related to cellular signal transduction (MAPK signaling pathway) and material metabolism (nitrogen metabolism, glycerol ester metabolism).It was also analyzed by WGCNA that two modules had the strongest correlation with physiological indicators. Eight candidate genes were identified among MAPK signaling pathway and the two modules.

Genomic Analysis and Expression Dynamics of GH3 Genes Under Abiotic Stresses in Brassica rapa

ABSTRACTIn silico characterization of the Gretchen Hagen3 (GH3) gene family is required for understanding phytohormone regulation and stress responses in Brassica rapa to develop the improved stress‐tolerant cultivars. The main objective of this research was to identify the key BrGH3 genes under different abiotic stresses. Using bioinformatics tools, a total of 27 BrGH3 genes were identified in B. rapa for which phylogenetic relationship, syntenic pairing, conserved motifs, miRNA regulation, and cis‐regulatory elements of BrGH3s were also studied. BrGH3 gene expression has been examined in numerous tissues and under various abiotic and phytohormone stressors. Phylogenetic studies separated BrGH3 genes into three major classes and nine subclasses based on gene functional evolution. Collinearity analysis demonstrated that all BrGH3 genes had syntenic linkage with AtGH3, BnaGH3, and BolGH3, indicating that genome duplication mechanisms were crucial to BrGH3 gene evolution. The expression dynamics of BrGH3 under diverse phytohormonal stresses methyl jasmonate (MeJA), auxin (IAA), abscisic acid (ABA), gibberellic acid (GA), and salicylic acid (SA) at different time intervals suggest that BrGH3‐5.1 has a consistently greater expression than other BrGH3 genes. Under salt, drought, and low temperature stress, BrGH3‐1 and BrGH3‐4 genes expressed comparatively higher. The findings suggest that five genes (BrGH3‐5.1, BrGH3‐5.2, BrGH3‐15, BrGH3‐17.2, and BrGH3‐19) have a key role in inducing broad stress resilience. These results can be beneficial in developing stress‐tolerant varieties of Chinese cabbage.

Genome-wide analysis of the WRKY gene family and their response to low-temperature stress in elephant grass.

Elephant grass (Cenchrus purpureus) is a perennial forage grass characterized by tall plants, high biomass and wide adaptability. Low-temperature stress severely limits elephant grass biomass and geographic distribution. WRKY is one of the largest families of plant-specific transcription factors and plays important roles in plant resistance to low-temperature. However, the understanding of the WRKY family in grasses is limited. In this study, we conducted a genome-wide characterization of WRKY proteins in elephant grass, including gene structure, phylogeny, expression, conserved motif organization, and functional annotation, to identify key CpWRKY candidates involved in cold tolerance. In this study, a total of 176 WRKY genes were identified in elephant grass. It was found that 172 were unevenly distributed across its 14 chromosomes, while the remaining 4 genes were not anchored to any chromosome. The genes were classified into three groups based on their WRKY conserved domains and zinc finger motifs. There were 12, 8, 19, 27, 12, 18 and 80 CpWRKYs belonging to group I, group IIa, group IIb, group IIc, group IId, group IIe and group III, respectively. We hypothesized that the ancient subgroup IIc WRKY gene is the ancestor of all WRKY genes in elephant grass. Most CpWRKYs in the same group have similar structure and motif composition. A total of 169 duplicate gene pairs were identified, suggesting that segmental duplication might have contributed to the expansion of the CpWRKY gene family. Ka/Ks analysis revealed that most of the CpWRKYs were subjected to purifying selection during the evolution. It was also found that six genes (CpWRKY51, CpWRKY81, CpWRKY100, CpWRKY101, CpWRKY140 and CpWRKY143) exhibited higher expression in roots compare to leaves, and were significantly induced by low temperature stress. Among them, CpWRKY81 had the highest expression under low-temperature stress, and its over-expression significantly enhanced the cold tolerance in yeast. In this study, we characterized WRKY genes in elephant grass and further investigated their physicochemical properties, evolution, and expression patterns under low-temperature stress. This research provides valuable resources for identifying key CpWRKY genes that contribute to cold tolerance in elephant grass.

Genome-Wide Identification and Characterization of Diterpenoid Pathway CYPs in Andrographis paniculata and Analysis of Their Expression Patterns under Low Temperature Stress

Andrographis paniculata is known for its diterpenoid medicinal compounds with antibacterial and anti-inflammatory properties. However, it faces production and cultivation challenges due to low temperatures (LTs). Cytochrome P450 monooxygenases (CYPs) are key enzymes in diterpenoid accumulation. Nevertheless, the functions and LT-related expression patterns of diterpenoid pathway CYPs in Andrographis paniculata remain poorly understood. In this study, 346 CYPs were discovered in Andrographis paniculata. Among them, 328 CYPs belonged to 42 known subfamilies. The remaining 17 CYPs might have represented novel subfamilies unique to this species. A total of 65 candidate CYPs associated with diterpenoid modification were identified. Of these, 50 were transmembrane proteins, and 57 were localized to chloroplasts. The CYP71 subfamily was the most abundant and had the highest motif diversity. Promoters of all candidate CYPs commonly contained elements responsive to gibberellins (GAs), methyl jasmonate (MeJA), and abiotic stresses. Notably, the XP_051152769 protein, corresponding to a CYP gene over 40,000 bp in length, featured an extraordinarily long intron (40,751 nts). Functional elements within this intron were related to LT, GAs, and dehydration pathways. Based on the promoter element arrangement and subfamily classification, 10 representative candidate CYPs were selected. Under LT stress, significant expression changes were observed in three representative CYPs: CYP71D, ent-kaurenoic acid oxidase (KAO), and ent-kaurene oxidase (KO). KAO and KO were significantly upregulated during early LT stress. KAO and KO interacted with each other and jointly interacted with GA20OX2-like. CYP71D acted as a negative response factor to LT stress. Among the 37 proteins interacting with CYP71D, 95% were CYPs. This study provides a critical preliminary foundation for investigating the functions of diterpenoid pathway CYPs in Andrographis paniculata, thereby facilitating the development of LT-tolerant cultivars.

Evolution and functional divergence of glycosyltransferase genes shaped the quality and cold tolerance of tea plants.

Plant glycosyltransferases (UGTs) play a key role in plant growth and metabolism. Here, we examined the evolutionary landscape among UGTs in 28 fully sequenced species from early algae to angiosperms. Our findings revealed a distinctive expansion and contraction of UGTs in the G and H groups in tea (Camellia sinensis), respectively. Whole-genome duplication and tandem duplication events jointly drove the massive expansion of UGTs, and the interplay of natural and artificial selection has resulted in marked functional divergence within the G group of the sinensis-type tea population. In Cluster II of group G, differences in substrate selection (e.g., Abscisic Acid) of the enzymes encoded by UGT genes led to their functional diversification, and these genes influence tolerance to abiotic stresses such as low temperature and drought via different modes of positive and negative regulation, respectively. UGTs in Cluster III of the G group have diverse aroma substrate preferences, which contributes a diverse aroma spectrum of the sinensis-type tea population. All Cluster III genes respond to low-temperature stress, whereas UGTs within Cluster III-1, shaped by artificial selection, are unresponsive to drought. This suggests that artificial selection of tea plants focused on improving quality and cold tolerance as primary targets.

Potential Regulatory Effects of Arbuscular Mycorrhizal Fungi on Lipid Metabolism of Maize in Response to Low-Temperature Stress.

The specific mechanisms underlying membrane lipid remodeling and changes in gene expression induced by arbuscular mycorrhizal fungi (AMF) in low-temperature-stressed plants are still unclear. In this study, physiological, transcriptomic, and lipidomic analyses were used to elucidate the physiological mechanisms by which AMF can enhance the adaptation of maize plants to low-temperature stress. The results showed that the relative electrical conductivity and malondialdehyde content of maize leaves were decreased after the inoculation with AMF, indicating that AMF reduced the peroxidation of membrane lipids and maintained the fluidity of the cell membrane. Transcriptomic analysis showed the presence of 702 differentially expressed genes induced by AMF in maize plants exposed to low-temperature stress. Furthermore, lipidomic analysis revealed changes in 10 lipid classes in AMF-inoculated maize plants compared with their noninoculated counterparts under low-temperature stress conditions. Lipid remodeling is an important strategy that arbuscular mycorrhizal plants adopt to cope with low-temperature stress.