Chlorophyll Synthesis Research Articles

Comparative transcriptome and metabolomic analysis reveal key genes and mechanisms responsible for the dark-green leaf color of a strawberry mutant

Photosynthesis is a source of energy for various types of plant life activities and is essential for plant growth and development. Consequently, the study of photosynthetic mechanisms has been a hot spot. Leaf color mutants has always been ideal materials for exploring the mechanisms of chlorophyll metabolism and photosynthesis. In this study, we identified a leaf color mutant of ‘Benihoppe’ strawberry in the field, which exhibited a darker green leaf color compared with the wild type. The content of total chlorophyll and carotenoid in the mutant leaves was elevated by 7.44–20.23% and 8.9–21.92%, respectively, compared with that of the wild type. Additionally, net photosynthetic rate in the mutant increased by 20.13%. Further transcriptome analysis showed that significant upregulation of genes such as GLK1, PPR, and MORF9 in the mutant leaves, which promoted chloroplast development. The expression levels of UROD, PPOC, PORA, CHLG, and CPOX were significantly upregulated during chlorophyll synthesis, while the expression levels of HCAR and CYP89A9 were significantly downregulated during chlorophyll degradation, thus leading to the accumulation of chlorophyll in mutant leaves. The upregulation of gene expression levels such as PetM, AtpD, PGK, and RPI4 during photosynthesis promoted multiple stages of light and dark reaction, thereby enhancing the photosynthetic capacity of the mutant. And the changes in metabolites such as monogalactosyl monoacylglycerol (MGMG), glucuronosyldiacylglycerol (GlcADG), raffinose, etc. also indicate that the mutant has metabolic differences in chloroplast composition and photosynthesis compared to ‘Benihoppe’. The above results not only deepen our understanding of the mechanism behind the dark-green leaf color in strawberry mutants but also provide potential genetic resources for cultivating strawberry varieties with enhanced photosynthetic capacity.

LcASR enhances tolerance to abiotic stress in Leymus chinensis and Arabidopsis thaliana by improving photosynthetic performance

SUMMARYAs a crucial forage grass, Leymus chinensis plays significant roles in soil and water conservation owing to its robust stress resistance. However, the underlying molecular mechanisms of its stress tolerance remain unclear. In this study, a novel gene, designated as LcASR (Abiotic Stress Resistance in Leymus chinensis), imparting resilience to both high light and drought, was identified. Under normal growth conditions, heterologous overexpression of LcASR in Arabidopsis (HO lines) showed no significant difference in appearance compared to wild‐type. Nevertheless, HO lines accumulate significantly higher chlorophyll content during the dark‐to‐light transition compared to the wild‐type, indicating that the LcASR protein participates in chlorophyll synthesis during chloroplast development. Meanwhile, transgenic Arabidopsis and L. chinensis plants exhibited resistance to abiotic stresses such as high light and drought. Photosystem complexes analysis revealed that LHCII proteins remained stable within their respective complexes during high light stress. We hypothesize that LcASR may play a role in fine tuning of chlorophyll synthesis to enable plant adaptation to diverse stress conditions. Moreover, overexpression of LcASR in L. chinensis led to agronomically valuable traits such as deeper green color, higher biomass accumulation, prolonged withering period, and extended grazing durations. This study uncovers a novel gene in L. chinensis that enhances forage yield and provides valuable genetic resources for sheepgrass breeding.

Integrative application of biochar and bacteria for mitigating antimony toxicity and bio-accessibility in sorghum.

Antimony (Sb) toxicity is a serious concern due to its harmful effects on humans and plants. Biochar (BC) has become a popular amendment for remediating soils polluted with metals and metalloids. However, the exact interaction mechanism between BC, microbes, and the remediation of Sb-polluted soils remains unclear. To address this, a study was performed to determine the impacts of maize straw BC and a bacterial strain (Pseudomonas frederiksbergensis: PF) in mitigating the harmful effects of Sb toxicity on sorghum productivity. A pot experiment was set up with the following treatments: control, soil contaminated with Sb (1000 mg kg-1), Sb-contaminated soil + BC (2 %), Sb-contaminated soil + PF, and Sb-contaminated soil + BC (2 %) + PF. Antimony toxicity significantly reduced sorghum biomass and grain yield while increasing hydrogen peroxide (H2O2: 32.63 %), malondialdehyde (MDA: 68.96 %) reducing chlorophyll a (95.65 %) and chlorophyll b synthesis (92 %), increasing Sb accumulation plant parts and decreasing NPK (24.48 %, 8.01 % and 19.24 %) and magnesium availability, soil organic carbon (SOC: 16.36 %), microbial biomass carbon (MBC: 10.80 %) and soil urease (76.31 %) and catalase (130.52 %) activity. The combined application of BC and bacteria enhanced the promoted sorghum biomass and grain production by improving chlorophyll synthesis, antioxidant activity, osmolyte production, nutrient availability, SOC, MBC, soil enzymatic activities and reducing both H2O2 and MDA production. Co-application of BC and bacteria decreased soil Sb concentration by 38.84 % while they decreased Sb concentration in sorghum root, stem, leaves and grains by 54.58 %, 34.15 %, 30.96 % and 54.58 % respectively. The decrease of Sb concentration in soil and plant parts with BC and bacteria application could be attributed to increase in soil pH, SOC, MBC, enzymes activities. Additionally, BC in combination with bacteria also reduced bio-accessible Sb concentration by 83.82 %, and bio-accessibility of Sb by 36.45 % indicating their appreciable potential to produce safer sorghum production in highly polluted Sb soil Therefore, BC and PF can be used together to improve sorghum production and develop environmentally friendly approaches in Sb-contaminated soils.

The Impacts of Volcanic Activity on Microbial Growth-A Simulation Experiment in the Qiliao Section in Shizhu County, Chongqing, China.

The impact of volcanic activity on microorganisms has always been a hot topic of discussion during geological history. Further studies are needed on the effects of volcanic activity on microbial growth in shale and the differences in nutrients provided by volcanic ash and other weathered rocks. This study's results indicated that TOC contents at the bottom of the shale layer are 1.93-4.44% and 3.0% on average. The TOC contents at the top of the layer are 3.38-5.13% and 4.0% on average. It indicated that TOC contents at the bottom of the shale layer are smaller than the TOC contents at the top of the layer, suggesting that volcanic activity posed a long-term effect on biological growth. Seven different leachate concentrations were set in this experiment as follows: 1/10, 1/100, 1/500, 1/1000, 1/1500, 1/2000, and 1/2500. The results showed that the growth status of Pseudourostyla crassipes was affected by the addition of leachates with different concentrations compared to the control group. Additionally, the synthesis of chlorophyll a by Anabaena pseudoichthyoides was the most efficient with the 1/10 volcanic ash leachate. Through the analysis of major and trace elements in the solution before labeland after cultivation, the main elemental content of Ca2+, Mg2+, Na+, and K+ decreased by 3.8~87.24%, 75.96~92.70%, 86.56~95.67%, and 5.42~20.52% in the solution after microbial growth respectively. The trace elements B, Ba, Zn, and Fe decreased by 27.54~94.39%, 20~82.03%, 70.45~98.29%, and 99%. It was found that the B, Ba, Fe, and Zn elements decreased significantly. The nutrients from volcanic ash are the main factor promoting microbial growth. It can be indicated that the volcanic ash soaking solution has a higher content of nutrients when compared to the solubility of nutrients in volcanic ash compared to that of granite. A higher content of nutrients promotes microbial growth. The calculation results indicate that a volcanic eruption with a quantity of several 1010 m3 has a significant impact on microorganisms, lasting from tens of thousands to hundreds of thousands of years.

SWATH-MS based proteomics reveals the role of photosynthesis related proteins and secondary metabolic pathways in the colored leaves of sweet olive (Osmanthus fragrans)

Colored leaves, a notable horticultural trait, have high research and ornamental value. The evergreen sweet olive (Osmanthus fragrans), one of the top ten traditional flowers in China, has been cultivated for more than two thousand years. However, in recent years, an increasing number of O. fragrans cultivars with colored leaves have been cultivated for their ornamental value. To study the molecular mechanism underlying the observed changes in leaf color, we selected O. fragrans ‘Yinbi Shuanghui’ (Y), which has yellow-white leaves, and O. fragrans ‘Sijigui’ (S), which has green leaves, as materials. Pigment content measurement showed that the chlorophyll, carotenoid and anthocyanin contents in Y were lower than in S. According to the SWATH-MS sequencing results, a total of 3,959 proteins were quantitatively identified, 1,300 of which were differentially expressed proteins (DEPs), including 782 up-regulated and 518 down-regulated proteins in Y compared to S. Functional enrichment analysis of DEPs revealed that down-regulated expression of photosynthesis related proteins may lead to the inhibition of chlorophyll synthesis in Y, this may be the main cause of leaf color change. Moreover, a protein interaction prediction model also showed that proteins such as PetC, PsbO, PsbP, and PsbQ were key proteins in the interaction network, and the up-regulated proteins participating in the anthocyanin and carotenoid pathways may be related to the formation of yellow-white leaves. Taken together, our findings represent the first SWATH-MS-based proteomic report on colored leaf O. fragrans and reveal that chlorophyll synthesis and secondary metabolism pathways contribute to the changes in leaf color.

Genome-wide identification of the eggplant jasmonate ZIM-domain (JAZ) gene family and functional characterization of SmJAZ10 in modulating chlorophyll synthesis in leaves.

The jasmonate ZIM-domain (JAZ) plays a crucial role in regulating several economic traits in crops. Despite its importance, the characterization of the SmJAZ gene family in eggplant (Solanum melongena L.) has not been documented. In this study, we identified 13 SmJAZ distributed across 9 chromosomes, which were categorized into 5 subgroups based on phylogenetic analysis. Both of them possess TIFY-motif and CCT_2 domains with varying degrees of variation. Promoter cis-element analysis predicted 42 distributed cis-elements that respond to diverse signals. Gene expression analysis demonstrated that SmJAZ exhibited responsiveness to JA, ABA, NaCl, PEG, 4 °C, blue light, and UV-B treatments. Moreover, microRNA interaction predictions identified 150 potential miRNAs, among which ath-miR5021 was found to target 8 SmJAZ mRNAs. Yeast two-hybrid assays demonstrated that most of the SmJAZs were able to interact with SmMYC2 and SmNINJA and could form JAZ-JAZ complexes. Subcellular localization analysis unveiled a diverse array of intranuclear and extranuclear localization signals for SmJAZs. Overexpressing of SmJAZ10 could decrease the chlorophyll content of seedling leaves, and the transcriptome showed that genes related to chlorophyll synthesis, such as SmCHLH, SmPORA, and SmGLK2, underwent down-regulated expression. Overall, these findings serve as a valuable resource for leveraging JA signaling to enhance eggplant quality.

Roles of Exogenous 5-Aminolevulinic Acid and Dihydroporphyrin Iron in Chlorophyll Precursor Synthesis and Chlorophyll-Related Enzyme Activities in Wheat Under Different Light Intensities

Aminolevulinic acid (5-ALA) and dihydroporphyrin iron chelates (DHFe) play roles in plant growth regulation under normal and stressful conditions. However, definitive data on their roles in regulating chlorophyll synthesis in wheat are lacking. In this study, the optimal concentrations for foliar-spray application of 5-ALA and DHFe to promote wheat seedling growth and leaf chlorophyll content were assessed. The optimal concentrations of 5-ALA or DHFe (50 mg/L and 0.01 mg/L, respectively) were applied as foliar sprays to seedlings of wheat ‘Bainong 4199’ (high light efficient) and ‘Zhoumai No. 18’ (average light efficient) under different light intensities. Chlorophyll precursor contents and activities of three chlorophyll synthesis-related enzymes were altered, and the combined application of 5-ALA and DHFe more strongly increased the leaf chlorophyll content. 5-ALA significantly increased the contents of the chlorophyll precursors porphobilinogen, uroporphyrinogen III, protoporphyrin IX, and magnesium-protoporphyrin IX, and the activities of 5-amino-ketovalerate dehydratase and uroporphyrinogen III synthase. DHFe resulted in an increase in chlorophyll content but a significant decrease in chlorophyllase activity and protochlorophyllide content. 5-ALA promoted the synthesis of chlorophyll precursors by regulating the activities of 5-amino-ketovalerate dehydratase and uroporphyrinogen III synthase. DHFe decreased chlorophyllase activity, thereby slowing chlorophyll degradation and increasing the chlorophyll content.

De-etiolation is Almost Colour Blind: the Study of Photosynthesis Awakening Under Blue and Red Light.

The synthesis and assembly of functioning photosynthetic complexes in chloroplasts developing from etioplasts during the de-etiolation of angiosperm seedlings are imperative for the plant's autotrophic lifestyle. This study compared de-etiolation process under monochromatic red or blue light of equal photon flux density during a 24-hour illumination period of etiolated Arabidopsis seedlings. The aim was to elucidate the impact of these light wavelength on the etioplast-to-chloroplast transformation and the initiation of light-dependent photosynthetic reactions. Both treatments lead to the formation of functional young chloroplasts; however, the etioplast-to-chloroplast transition and the assembly of photosynthetic complexes occurred unevenly, with individual steps tuned by red or blue light. Ultrastructural analysis suggested faster prolamellar bodies disassembly under blue light, while low temperature fluorescence studies indicated a slower transformation of protochlorophyllide to chlorophyllide, and chlorophyll a, under these conditions. Red light further promoted the synthesis of chlorophyll b and LHCII antenna proteins. However, the efficiency of antennae in dissipating excess absorbed energy was higher for seedlings de-etiolated under blue light; the maximum quantum yield of the photosystem II reached 0.81 after 24-hour de-etiolation, equivalent to mature plants. Blue light seemed to enhance the development of well-functioning photosystems (I and II) and antennae. These findings are important for gaining a deeper understanding of photoreceptor regulation of de-etiolation and for utilizing selected light regimes to improve crop yield.

Citrus yellow vein clearing virus infection triggers phloem remobilization of iron- and zinc-nicotianamine in citrus.

Citrus yellow vein clearing virus (CYVCV) is a worldwide and highly destructive disease of citrus, but the mechanisms involved in CYVCV-inhibited plant growth are not well understood. This study examined nutrient levels and their cellular distribution in different organs of healthy and CYVCV-affected citrus (Citrus reticulata 'Kanpei') plants. We found that CYVCV-infected plants exhibit characteristic symptoms, including a significant reduction in iron (Fe) and other elemental nutrients in the shoots. Our data suggest that CYVCV-induced chlorosis in citrus leaf veins is primarily due to iron deficiency, leading to reduced chlorophyll synthesis. Further analysis revealed a marked decrease in iron concentration within the pith and xylem of citrus petioles post-CYVCV infection, contrasting with increased Fe and zinc (Zn) concentrations in the phloem. Moreover, a substantial accumulation of starch granules was observed in the pith, xylem, and phloem vessels of infected plants, with vessel blockage due to starch accumulation reaching up to 81%, thus significantly obstructing Fe transport in the xylem. Additionally, our study detected an upregulation of genes associated with nicotinamide metabolism and Fe and Zn transport following CYVCV infection, leading to increased levels of nicotinamide metabolites. This suggests that CYVCV-infected citrus plants may induce nicotinamide synthesis in response to Fe deficiency stress, facilitating the transport of Fe and Zn in the phloem as nicotinamide-bound complexes. Overall, our findings provide insight into the mechanisms of long-distance Fe and Zn transport in citrus plants in response to CYVCV infection and highlight the role of nutritional management in mitigating the adverse effects of CYVCV, offering potential strategies for cultivating CYVCV-resistant citrus varieties.

Overexpression of the persimmon ABA receptor DkPYL3 gene alters fruit development and ripening in transgenic tomato

Abscisic acid (ABA) is a crucial plant hormone that regulates various aspects of plant development. However, the specific function of the ABA receptor PYL in fruit development has not been fully understood. In this study, we focused on DkPYL3, a member of the ABA receptor subfamily Ⅰ in persimmon, which exhibited high expression levels in fruit, particularly during the young fruit and turning stages. Through yeast two-hybrid (Y2H), firefly luciferase complementation imaging (LCI), protein inhibition assays, and RNA-seq techniques, we identified and characterized the DkPYL3 protein, which was found to inhibit the activity of protein phosphatase type 2 C (PP2C). By heterologous overexpressing (OE) persimmon DkPYL3 in tomatoes, we investigated the impact of the DkPYL3 gene on fruit development and ripening. DkPYL3-OE upregulated the expression of genes related to chlorophyll synthesis and development, leading to a significant increase in chlorophyll content in young fruit. Several fruit quality parameters were also affected by DkPYL3 expression, including sugar content, single fruit weight, and photosynthesis rate. Additionally, fruits overexpressing DkPYL3 exhibited earlier ripening and higher levels of carotenoids and flavonoids compared to wild-type fruits. These results demonstrate the pivotal role of DkPYL3 in ABA-mediated young fruit development, ripening onset, and fruit quality in transgenic tomatoes.

Hydrogen peroxide participates in leaf senescence by inhibiting CHLI1 activity.

Hydrogen peroxide promoted leaf senescence by sulfenylating the magnesium chelating protease I subunit (CHLI1) in the chlorophyll synthesis pathway, and inhibited its activity to reduce chlorophyll synthesis. Leaf senescence is the final and crucial stage of plant growth and development, during which chlorophyll experiences varying degrees of destruction. It is well-known that the higher ROS accumulation is a key factor for leaf senescence, but whether and how ROS regulates chlorophyll synthesis in the process are unknown. Here, we report that H2O2 inhibits chlorophyll synthesis during leaf senescence via the I subunit of magnesium-chelatase (CHLI1). During leaf senescence, the decrease of chlorophyll content is accompanied by the increase of H2O2 accumulation, as well as the inhibition of catalase (CAT) genes expression. The mutant cat2-1, with increased H2O2 shows an accelerated senescence phenotype and decreased CHLI1 activity compared with the wild type. H2O2 inhibits CHLI1 activity by sulfenylating CHLI1 during leaf senescence. Consistent with this, the chli1 knockout mutant displays the same premature leaf senescence symptom as cat2-1, while overexpression of CHLI1 in cat2-1 can partially restore its early senescence phenotype. Taken together, these results illustrate that CAT2-mediated H2O2 accumulation during leaf senescence represses chlorophyll synthesis through sulfenylating CHLI1, and thus inhibits its activity, providing a new insight into the pivotal role of chlorophyll synthesis as a participant in orchestrating the leaf senescence.

Hormonal signaling regulates photosynthetic function of alfalfa (Medicago sativa L.) under NaHCO3 stress

The physiological and molecular mechanisms underlying salt-alkali tolerance in Medicago sativa are of significant importance for the development of animal husbandry on salt-alkali lands and the restoration of vegetation in such areas. This study utilized salt-alkali tolerance Medicago sativa 'Zhaodong' (ZD) and salt-alkali sensitive variety M. sativa 'Zhongmu No.1′ (ZM) as materials. Physiological analyses, transcriptomic sequencing, and hormone-targeted metabolomics techniques were employed to investigate the differential responses of the two alfalfa varieties to NaHCO3 stress in terms of morphology, photosynthetic functionality, and oxidative damage indicators. Additionally, weighted gene co-expression network analysis (WGCNA) was utilized to elucidate key mechanisms underlying salt-alkali tolerance in alfalfa. The results indicate that NaHCO3 stress leads to photosynthetic inhibition and oxidative damage in alfalfa leaves. Under NaHCO3 stress, PSI in alfalfa leaves exhibits higher stability compared to PSII. The salt-alkali tolerance alfalfa variety ZD demonstrates stronger tolerance compared to the salt-alkali sensitive variety ZM. Furthermore, differentially expressed genes (DEGs) between the two varieties under NaHCO3 stress are primarily enriched in KEGG pathways such as chlorophyll synthesis, photosynthesis, carbon fixation, and plant hormone synthesis and signaling. Weighted gene co-expression network analysis (WGCNA) was conducted based on physiological and transcriptomic data. Most differentially expressed genes (DEGs) in the top two modules with the highest correlation to physiological indicators such as photosynthesis are enriched in hormone synthesis and signal transduction pathways. Additionally, key transcription factors involved in hormone signal transduction were identified within these modules, such as MYC2 and ABI5, which regulate jasmonic acid (JA) and abscisic acid (ABA) signaling, respectively. These findings suggest that plant hormone signaling may play a critical role in regulating salt-alkali tolerance in alfalfa. Further analysis was conducted on plant hormone levels and gene expression involved in biosynthesis and signal transduction processes. The results indicate that NaHCO3 stress leads to significant accumulation of ABA and JA content in alfalfa leaves. The biosynthesis and signal transduction pathways of ABA and JA are activated under NaHCO3 stress. Additionally, the salt-alkali tolerance alfalfa variety ZD exhibits a more sensitive response to ABA and JA signals compared to ZM. Salicylic acid (SA) shows a positive response to NaHCO3 stress only in the ZD variety, which may be one of the key reasons for its stronger salt-alkali tolerance. Under NaHCO3 stress, overall growth-promoting hormones (IAA, GA, CK) are downregulated in ZD but upregulated in ZM, indicating that the salt-alkali tolerance alfalfa variety ZD mainly regulates the balance between growth and resistance by modulating the ratio of growth-promoting and stress-related hormones in response to NaHCO3 stress. This study reveals that hormone signaling plays a key role in regulating the photosynthetic function of alfalfa in response to salt-alkali stress, which provides theoretical basis and clues for the molecular breeding of alfalfa for salt-alkali tolerance.

Effect of Partial Knockout of the Plastid Starch Phosphorylase Gene NtPHO1-L1 on the Metabolism of Carbohydrates and Carotenoids in Nicotiana tabacum L. Leaves

Starch metabolism is regulated by a complex catalytic network, one of the key enzymes of which is the plastid starch phosphorylase PHO1. In this study, using the CRISPR-Cas9 system, we obtained tobacco (Nicotiana tabacum L.) plants with a partial knockout of the NtPHO1-L1 gene due to deletion variants of the catalytic domain of the NtPHO1-L1 protein, leading to the formation of nonfunctional forms of the enzyme. The edited lines differed from wild-type plants by increased starch accumulation and decreased content of sugars, chlorophylls, and carotenoids in the leaves. It was shown that, compared to the control, the edited plants were characterized by differential expression of starch (NtPHO1-L1, NtGWD, NtBAM1, NtBAM9, NtAI) and carotenoid (NtPSY2, NtPDS, NtZDS, NtCRTISO, NtVDE) metabolism genes, as well as genes encoding MADS-domain transcription factors (NtFUL1, NtSEP1, NtSEP2, NtSEP3), which are presumably involved in the regulation of transcription of the studied metabolic genes. These data suggest that partial knockout of NtPHO1-L1 alters the functional activity of tobacco starch phosphorylase. This, in turn, may influence the coordinated activity of starch catabolism enzymes, as well as chlorophyll and carotenoid synthesis enzymes, possibly through differential expression of MADS-box genes. The results highlight the critical regulatory role of plastid starch phosphorylase in transient starch metabolism and in stimulating plant photosynthesis.

Performance of the edible halophyte Cakile maritima under critical magnesium and potassium thresholds

In their natural biotope, plants are challenged with low nutrient availability which is one of the most important limiting factors for plant production. Nutrient limitation causes disruption in several metabolic pathways resulting in a decrease in plant growth and establishment. Such responses were mostly studied in glycophytes while in halophytes the data remained scare. In the present investigation, using Cakile maritima as a plant model for halophytes, we attempt to elucidate the behavior of this species under critical magnesium and potassium thresholds. Our data showed that low K or Mg supply (0.01 mM) reduced leaf number and biomass production in leaves, stems and roots while both parameters were improved at 0.05 mM Mg and K concentration before reaching an optimum at 0.25 mM Mg and 1 mM K, respectively. Several indices of K and Mg stress tolerance were reduced upon deficiency in both elements and were significantly improved by moderate K and Mg supply. Photosynthetic pigment content was reduced upon both deficiencies with the highest reductions recorded in plants suffering from severe Mg and K starvation. Increasing Mg and K supply resulted in better chlorophyll synthesis as reflected by the increase in chlorophyll stability index parameter (CSI). Furthermore, both deficiencies triggered oxidative damages as malondialdehyde content (MDA) and electrolyte leakage (EL) increased while membrane stability index (MSI) decreased under both deficiencies. Such results suggested that the cell redox homeostasis was altered when Mg and K were omitted from the nutrient solution. Interestingly, moderate and high Mg and K concentrations promoted C. maritima growth and reduced the oxidative damage caused by the lack of both elements in the external medium. Overall, C. maritima exhibited a typical halophytic behaviour, requiring less macroelements to express its growth performance when cultivated under critical magnesium and potassium thresholds.

Genome-Wide Identification of the Auxin Response Factor Gene Family in Maple (Acer truncatum) and Transcriptional Expression Analysis at Different Coloration Stages of Leaves

Auxin response factors (ARFs) are involved in the mechanism of plant leaf color regulation, inhibiting chlorophyll synthesis while promoting anthocyanin production. However, it is not clear whether the ARF gene family is involved in autumn leaf color changes in maple. The differentially expressed genes for autumn leaf discoloration were obtained by transcriptome sequencing, and the AtARF family was constructed by homologous gene search. The results show that the AtARFs consist of 21 members distributed on 11 chromosomes and can be divided into three subfamilies, which are mainly distributed in the nucleus. The promoter regions of the AtARFs contain light-responsive elements, abiotic stress-responsive elements, and hormone-responsive elements. The analyses presented in this paper provide comprehensive information on ARFs and help to elucidate their functional roles in leaf color change in Acer truncatum.

Transcriptome Analysis Revealed the Anabolic Regulation of Chlorophyll and Carotenoids in Curcuma alismatifolia Bracts.

Curcuma alismatifolia is an attractive ornamental plant in the ginger family. Its bracts come in a variety of colors and are commonly used as cut flowers, potted plants, and landscaping. To investigate the regulation of bract pigmentation in C. alismatifolia, we examined the pigment levels of chlorophyll and carotenoids in the pure color part (PC) and variegated part (VA) of three C. alismatifolia varieties, i.e., "Siam TM Sitrone," "Chiang Mai Pink," and "Snow White." To mine the color mechanisms of the pure color and variegated parts of the bract, we conducted RNA-seq analysis on C. alismatifolia. We identified a total of 89,975 unigenes, and there were 3584 differentially expressed genes identified post-screening. Furthermore, 1858 DEGs were annotated in the GO database and 681 in the KEGG database. We pinpointed key genes responsible for the diverse bract colors in C. alismatifolia, including ZEP for carotenoid synthesis and GAGA2 in the chlorophyll synthesis pathway. This study provides valuable insights into understanding the pigmentation mechanism of bracts in C. alismatifolia and the breeding process.

The combined effects of copper and zinc on Arabidopsis involve differential regulation of chlorophyll synthesis and photosystem function

Copper (Cu) and zinc (Zn) are both oxidation-reducing metal elements that are necessary for plant growth, and their effect often depends on their concentration. However, there are few studies that have investigated how plants are stressed and affected when the two ions are present simultaneously, especially when one ion is beneficial due to a low concentration and the other is detrimental due to a high concentration. To address this question, we treated Arabidopsis plants with either high or/and low concentrations of the two ions and investigated their mutual effects and the underlying molecular mechanism, focusing on photosynthetic function. The results showed that the photosynthetic pigment content and the performance of photosynthetic systems were most affected when both metal ions were present at detrimental concentrations (60 μM Cu for Cu60 and 350 μM Zn for Zn350). These include the effective openness of the photoreaction center, the electron transport rate and efficiency of photosystem II (PSII), the NPQ-dependent energy dissipation and the activity of photosystem I (PSI). However, when the harmful concentration of one of the two metals is combined with the beneficial concentration of the other metal (Cu5+Zn350 or Zn50+Cu60), these photosynthetic indicators are compensated to different degrees but the negative effects of copper ions at high dose are more difficult to eliminate than zinc ions. These results were also confirmed by gene expression analysis, which provides a clue to understanding the interaction between heavy metal ions, reducing metal toxicity and improving the tolerance of plants to heavy metals in practice.

The transcription factor RppA regulates chlorophyll and carotenoid biosynthesis to improve photoprotection in cyanobacteria.

Chlorophyll is an essential photosynthetic pigment but also a strong photosensitizer. Excessive free chlorophyll and its precursors can cause oxidative damage to photosynthetic organisms. Cyanobacteria are the oldest oxygenic photosynthetic organisms and the ancestors of the chloroplast. Owing to their complex habitats, cyanobacteria require precise regulation of chlorophyll synthesis to respond to environmental factors, especially changes in light. Chlorophyll synthase, encoded by chlG, is the enzyme catalyzing the final step of chlorophyll biosynthesis, which is closely related to photosynthesis biogenesis. However, the transcriptional regulation on chlG remains unclear. Here, the transcription factor, regulator of photosynthesis and photopigment-related gene expression A (RppA) was identified to bind to the chlG promoter by screening a yeast one-hybrid library in the cyanobacterium Synechocystis sp. PCC 6803. The rppA knock-out mutant showed a phenotype of slow growth and severe oxidative damage under dark-light transition conditions. The up-regulated transcriptional expression of chlG was significantly higher and more chlorophyll and its precursors accumulated in the rppA knock-out mutant than those in the wild-type strain during the transition from darkness to light, indicating RppA represses the expression of chlG in Synechocystis. Meanwhile, RppA could synchronously promote the transcription of carotenoids biosynthesis-related genes to enhance carotenoids synthesis during the dark-light transition. These results reveal synergistic regulation of chlorophyll and carotenoids biosynthesis in cyanobacteria in response to frequent dark-light transitions, which slows down chlorophyll biosynthesis while promoting carotenoids biosynthesis to avoid oxidative damage caused by excessive reactive oxygen species accumulation.

Biosynthesis and Extraction of Chlorophyll, Carotenoids, Anthocyanins, and Betalaine In Vivo and In Vitro.

As natural bioactive compounds, plant pigments play crucial roles not only in plant phenotype, growth, development, and adaptation to stress but also hold unique value in biotechnology, healthcare, and industrial applications. There is growing interest in the biosynthesis and acquisition of plant pigments. Thus, this paper explores emerging extraction methods of natural pigments and elucidates the biosynthesis pathways of four key plant pigments, chlorophylls, carotenoids, anthocyanins, and betalaine in vivo and in vitro. We comprehensively discuss the application of solvent, supercritical fluid [extraction], ultrasonic, and microwave-assisted extraction techniques, as well as introducing key enzymes, precursors, and synthetic pathways involved in pigment synthesis. δ-Aminolevulinic acid represents a pivotal initiating enzyme for chlorophyll synthesis, whereas isopentenylpyrophosphate, (IPP) and dimethylallyl pyrophosphate, (DMAPP) are closely associated with carotenoid biosynthesis. Phenylalanine and tyrosine are critical substances for anthocyanin and betalaine synthesis, respectively. Hence, crucial genes such as chlI, crtB, PGT8, CYP76AD1, and BvDODA can be employed for heterologous biosynthesis in vitro to meet the demand for increased plant pigment amount. As a pivotal determinant of plant coloration, an in-depth exploration into the high-quality acquisition of plant pigments can provide a basis for developing superior pigments and offer new insights into increasing pigment yield.

Effects of LED polarized and vortex light on growth and photosynthetic characteristics of pepper (Capsicum annuum L.)

Most studies currently focus on traditional illuminant regulating plant growth, while less attention has been given to the LED internal luminescence. This study examined how polarized and vortex light affect the growth and photosynthetic traits of pepper plants, with LED light used as the control. The findings indicated that circular polarized light significantly increased the aboveground biomass of pepper. Additionally, both polarized and vortex light treatment significantly influenced the root development of pepper. In comparison to the control group, the chlorophyll content was highest under circular polarized light, while the Pn, Sc, Tr, and Ci values were highest under linear polarized light, and the enzyme activity of Rubisco was increased. Circular polarized light notably increased the activities of POD, CAT, and SOD, the activity of SOD reached its peak under the left vortex light. Moreover, the content of MDA was observed to be the lowest under linear and right vortex light treatments. The expressions of key genes for chlorophyll synthesis (CaHEMA1 and CaCAO) and antioxidant enzyme synthesis (CaPOD, CaSOD, and CaMDHAR) were significantly altered under varying polarized light conditions, The latter genes, which play crucial roles in antioxidant enzyme activity, also showed significant variations in response to different polarized light treatments. In conclusion, polarized light significantly impacts the growth of pepper and is anticipated to be utilized for plant growth, setting the stage for future research in this area.