Prunus mume is an ecologically and economically valuable plant with both medicinal and edible values. However, drought severely limits the promotion and cultivation of P. mume in the arid and semi-arid areas in northern China. In this study, we treated P. mume 'Meiren' with natural drought and then assessed photosynthetic and physiological indexes such as osmoregulatory substances, photosynthetic parameters, and antioxidant enzyme activities. Furthermore, we employed transcriptome sequencing to explore the internal regulatory mechanism of P. mume under drought stress. As the drought stress aggravated, the levels of chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll (a+b)[Chl(a+b)], and soluble protein (SP) in P. mume first elevated and then declined. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum photochemical efficiency (Fv/Fm), effective photochemical quantum yield [Y(Ⅱ)], photochemical quenching (qP), and relative electron transport rate (ETR) all kept decreasing, while the levels of malondialdehyde, superoxide dismutase (SOD), peroxidase (POD), and osmoregulatory substances rose. Transcriptome sequencing revealed a total of 24 853 high-quality genes. Gene ontology (GO) enrichment showed that differentially expressed genes (DEGs) were the most under severe drought. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed that the DEGs during the four drought periods were mainly involved in the biosynthesis of secondary metabolites, plant-pathogen interaction, plant hormone signal transduction, starch and sucrose metabolism, and mitogen-activated protein kinase signaling pathways. Furthermore, we identified 16 key genes associated with the drought tolerance of P. mume 'Meiren'. This study discovered that P. mume might up-regulate or down-regulate the expression of drought tolerance-related genes such as SUS, P5CS, LEA, SOD, POD, SOD1, TPPD, and TPPA via transcription factors like MYB, ERF, bHLH, NAC, and WRKY to promote the accumulation of osmoregulatory substances like sucrose and enhance the activities of antioxidant enzymes such as SOD and POD, thus reducing the harm of reactive oxygen species and protecting the structure and function of the membrane system under drought stress. The findings provide theoretical references for further exploration of candidate genes of P. mume in response to drought stress and breeding of drought-tolerant varieties.
Droughts ; Photosynthesis/physiology* ; Gene Expression Regulation, Plant ; Stress, Physiological/genetics* ; Prunus/genetics* ; Chlorophyll/metabolism* ; Plant Proteins/genetics*

Microalgae possess high photosynthetic efficiency, robust adaptability, and substantial biomass, serving as excellent biological resources for large-scale cultivation. Malic enzyme (ME), a ubiquitous metabolic enzyme in living organisms, catalyzes the decarboxylation of malate to produce pyruvate, CO₂, and NAD(P)H, playing a role in multiple metabolic pathways including energy metabolism, photosynthesis, respiration, and biosynthesis. In this study, we identified the Scenedesmus quadricauda malic enzyme gene (SqME) and its biological functions, aiming to provide excellent target genes for the genetic improvement of higher plants. Based on the RNA-seq data from S. quadricauda under the biofilm cultivation mode with high CO₂ and light energy transfer efficiency and small water use, a highly expressed gene (SqME) functionally annotated as ME was cloned. The physicochemical properties of the SqME-encoded protein were systematically analyzed by bioinformatics tools. The subcellular localization of SqME was determined via transient transformation in Nicotiana benthamiana leaves. The biological functions of SqME were identified via genetic transformation in Nicotiana tabacum, and the potential of SqME in the genetic improvement of higher plants was evaluated. The ORF of SqME was 1 770 bp, encoding 590 amino acid residues, and the encoded protein was located in chloroplasts. SqME was a NADP-ME, with the typical structural characteristics of ME. The ME activity in the transgenic N. tabacum plant was 1.8 folds of that in the wild-type control. Heterologous expression of SqME increased the content of chlorophyll a, chlorophyll b, and total chlorophyll by 20.9%, 26.9%, and 25.2%, respectively, compared with the control. The transgenic tobacco leaves showed an increase of 54.0% in the fluorescence parameter NPQ and a decrease of 30.1% in Fo compared with the control. Moreover, the biomass, total lipids, and soluble sugars in the transgenic tobacco leaves enhanced by 20.5%, 25.7%, and 9.5%, respectively. On the contrary, the starch and protein content in the transgenic tobacco leaves decreased by 22.4% and 12.2%, respectively. Collectively, the SqME-encoded protein exhibited a strong enzymatic activity. Heterologous expressing of SqME could significantly enhance photosynthetic protection, photosynthesis, and biomass accumulation in the host. Additionally, SqME can facilitate carbon metabolism remodeling in the host, driving more carbon flux towards lipid synthesis. Therefore, SqME can be applied in the genetic improvement of higher plants for enhancing photosynthetic carbon fixation and lipid accumulation. These findings provide scientific references for mining of functional genes from S. quadricauda and application of these genes in the genetic engineering of higher plants.
Nicotiana/genetics* ; Photosynthesis/physiology* ; Malate Dehydrogenase/biosynthesis* ; Plant Leaves/genetics* ; Scenedesmus/enzymology* ; Carbon Cycle/genetics* ; Lipid Metabolism/genetics* ; Plants, Genetically Modified/metabolism*

Photosynthesis in plants directly affects the synthesis and accumulation of organic matter, which directly influences crop yield. RNA-binding proteins (RBPs) are involved in the regulation of a variety of physiological functions in plants, while the functions of RBPs in photosynthesis have not been clearly elucidated. To investigate the effect of a glycine-rich RNA-binding protein (SlRBP1) in tomato on plant photosynthesis, a stably inherited SlRBP1 silenced plant in Alisa Craig was obtained by plant tissue culture using artificial small RNA interference. It turns out that the size of the tomato fruit was reduced and leaves significantly turned yellow. Chlorophyll(Chl) content measurement, Chl fluorescence imaging and chloroplast transmission electron microscopy revealed that the chloroplast morphology and structure of the leaves of tomato amiR-SlRBP1 silenced plants were disrupted, and the chlorophyll content was significantly reduced. Measurement of photosynthesis rate of wild-type and amiR-SlRBP1 silenced plants in the same period demonstrated that the photosynthetic rate of these plants was significantly reduced, and analysis of RNA-seq data indicated that silencing of SlRBP1 significantly reduced the expression of photosynthesis-related genes, such as PsaE, PsaL, and PsbY, and affected the yield of tomato fruits through photosynthesis.
RNA ; Solanum lycopersicum/genetics* ; Photosynthesis/genetics* ; Chlorophyll ; RNA-Binding Proteins/genetics*

Cyanobacteria are the only prokaryotes capable of oxygenic photosynthesis, which have potential to serve as "autotrophic cell factories". However, the synthesis of biofuels and chemicals using cyanobacteria as chassis are suffered from poor stress tolerance and low yield, resulting in low economic feasibility for industrial production. Thus, it's urgent to construct new cyanobacterial chassis by means of synthetic biology. In recent years, adaptive laboratory evolution (ALE) has made great achievements in chassis engineering, including optimizing growth rate, increasing tolerance, enhancing substrate utilization and increasing product yield. ALE has also made some progress in improving the tolerance of cyanobacteria to high light intensity, heavy metal ions, high concentrations of salt and organic solvents. However, the engineering efficiency of ALE strategy in cyanobacteria is generally low, and the molecular mechanisms underpinning the tolerance to various stresses have not been fully elucidated. To this end, this review summarizes the ALE-associated technical strategies and their applications in cyanobacteria chassis engineering, following by discussing how to construct larger ALE mutation library, increase mutation frequency of strains and shorten evolution time. Moreover, exploration of the construction principles and strategies for constructing multi-stress tolerant cyanobacteria, and efficient analysis the mutant libraries of evolved strains as well as construction of strains with high yield and strong robustness are discussed, with the aim to facilitate the engineering of cyanobacteria chassis and the application of engineered cyanobacteria in the future.
Technology ; Photosynthesis/genetics* ; Cyanobacteria/genetics* ; Light ; Biofuels

In order to investigate the molecular mechanism of silk/threonine protein kinase (STK)-mediated blue light response in the algal Chlamydomonas reinhardtii, phenotype identification and transcriptome analysis were conducted for C. reinhardtii STK mutant strain crstk11 (with an AphvIII box reverse insertion in stk11 gene coding region) under blue light stress. Phenotypic examination showed that under normal light (white light), there was a slight difference in growth and pigment contents between the wild-type strain CC5325 and the mutant strain crstk11. Blue light inhibited the growth and chlorophyll synthesis in crstk11 cells, but significantly promoted the accumulation of carotenoids in crstk11. Transcriptome analysis showed that 860 differential expression genes (DEG) (559 up-regulated and 301 down-regulated) were detected in mutant (STK4) vs. wild type (WT4) upon treatment under high intensity blue light for 4 days. After being treated under high intensity blue light for 8 days, a total of 1 088 DEGs (468 upregulated and 620 downregulated) were obtained in STK8 vs. WT8. KEGG enrichment analysis revealed that compared to CC5325, the crstk11 blue light responsive genes were mainly involved in catalytic activity of intracellular photosynthesis, carbon metabolism, and pigment synthesis. Among them, upregulated genes included psaA, psaB, and psaC, psbA, psbB, psbC, psbD, psbH, and L, petA, petB, and petD, as well as genes encoding ATP synthase α, β and c subunits. Downregulated genes included petF and petJ. The present study uncovered that the protein kinase CrSTK11 of C. reinhardtii may participate in the blue light response of algal cells by mediating photosynthesis as well as pigment and carbon metabolism, providing new knowledge for in-depth analysis of the mechanism of light stress resistance in the algae.
Chlamydomonas reinhardtii/genetics* ; Photosynthesis/genetics* ; Plants/metabolism* ; Protein Kinases ; Threonine/metabolism* ; Carbon/metabolism* ; Serine/metabolism*

Pinellia ternata is an important medicinal plant, and its growth and development are easily threatened by high temperature. In this study, comprehensive research on physiological, cytological and transcriptional responses to different levels of heat stress were conducted on a typical phenotype of P. ternata. First, P. ternata exhibited tolerance to the increased temperature, which was supported by normal growing leaves, as well as decreased and sustained photosynthetic parameters. Severe stress aggravated the damages, and P. ternata displayed an obvious leaf senescence phenotype, with significantly increased SOD and POD activities (46% and 213%). In addition, mesophyll cells were seriously damaged, chloroplast thylakoid was fuzzy, grana lamellae and stroma lamellae were obviously broken, and grana thylakoids were stacked, resulting in a dramatically declined photosynthetic rate (74.6%). Moreover, a total of 16 808 genes were significantly differential expressed during this process, most of which were involved in photosynthesis, transmembrane transporter activity and plastid metabolism. The number of differentially expressed transcription factors in MYB and bHLH families was the largest, indicating that these genes might participate in heat stress response in P. ternata. These findings provide insight into the response to high temperature and facilitate the standardized cultivation of P. ternata.
Pinellia/genetics* ; Heat-Shock Response/genetics* ; Photosynthesis/genetics* ; Plants, Medicinal/genetics* ; Phenotype

GLKs (GOLDEN 2-LIKEs) are a group of plant-specific transcription factors regulating the chloroplast biogenesis, differentiation and function maintains by triggering the expression of the photosynthesis-associated nuclear genes (PhANGs). The GLKs also play important roles in nutrient's accumulation in fruits, leaf senescence, immunity and abiotic stress response. The expression of GLK genes were affected by multiple hormones or environmental factors. Therefore, GLKs were considered as the key nodes of regulatory network in plant cells, and potential candidates to improve the photosynthetic capacity of crops. Since numerous researches of GLKs have been reported in plants, the biological function, molecular mechanism of GLKs genes and its applications in breeding were summarized and a GLK-mediated signaling network model was developed. This review may facilitate future research and application of GLKs.
Chloroplasts/genetics* ; Gene Expression Regulation, Plant ; Photosynthesis/genetics* ; Plant Breeding ; Transcription Factors/metabolism*

Grape (Vitis vinifera L.) in production is frequently exposed to inadequate light, which significantly affects its agronomic traits via inhibiting their physiological, metabolic and developmental processes. To explore the mechanism how the grape plants respond to the weak light stress, we used 'Yinhong' grape and examined their physiology-biochemistry characteristics and transcriptional profile under different levels of weak light stress. The results showed that grape seedlings upon low intensity shading treatments were not significantly affected. As the shading stress intensity was strengthened, the epidermis cells, palisade tissue, and spongy tissue in the leaves were thinner, the intercellular space between the palisade tissue and spongy tissue was larger compared with that of the control, and the activities of superoxide dismutase, catalase and peroxidase were decreased gradually. Additionally, the soluble protein content increased and the free proline content decreased gradually. Compared with the control, significant changes in plant photosynthetic characteristics and physiology-biochemistry characteristics were observed under high intensity of shading (80%). RNA-seq data showed that the differentially expressed genes between CK and T2, CK and T4, T2 and T4 were 13 913, 13 293 and 14 943, respectively. Most of the enrichment pathways were closely related with the plant's response to stress. Several signaling pathways in response to stress-resistance, e.g. JA/MYC2 pathway and MAPK signal pathway, were activated under weak light stress. The expression level of a variety of genes related to antioxidation (such as polyphenol oxidase and thioredoxin), photosynthesis (such as phytochrome) was altered under weak light stress, indicating that 'Yinhong' grape may activate the antioxidation related pathways to cope with reactive oxygen species (ROS). In addition, it may activate the expression of photosynthetic pigment and light reaction structural protein to maintain the photosynthesis activity. This research may help better understand the relevant physiological response mechanism and facilitate cultivation of grape seedlings under weak light.
Vitis/metabolism* ; Gene Expression Regulation, Plant ; Photosynthesis/genetics* ; Plant Leaves ; Light ; Seedlings/metabolism*

Lactate is an important industrial chemical and widely used in various industries. In recent years, with the increasing demand for polylactic acid (PLA), the demand for lactate raw materials is also increasing. The contradiction between the high cost and the market demand caused by the heterotrophic production of lactate attracts researchers to seek other favorable solutions. The production of lactate from photosynthetic carbon fixation by cyanobacteria is a potential new raw material supply strategy. Based on the photosynthetic autotrophic cell factory, it can directly produce high optical purity lactate from carbon dioxide on a single platform driven by solar energy. The raw materials are cheap and easy to obtain, the process is simple and controllable, the products are clear and easy to separate, and the double effects of energy saving and emission reduction and production of high value-added products are achieved at the same time, which has important research and application value. This paper reviews the development history of cyanobacteria carbon sequestration to produce lactate, summarizes its research progress and encounters technical difficulties from the aspects of metabolic basis, metabolic engineering strategy, metabolic kinetics analysis and technical application, and prospects the future of this technology.
Carbon Cycle ; Carbon Dioxide ; Cyanobacteria/genetics* ; Lactic Acid ; Metabolic Engineering ; Photosynthesis

Rice leaf color mutants play a great role in research about the formation and development of chloroplasts and the genetic mechanism of the chlorophyll (Chl) metabolism pathway. pgl3 is a rice leaf color mutant derived from Xiushui11 (Oryza sativa L. spp. japonica), treated with ethyl methane sulfonate (EMS). The mutant exhibited a pale-green leaf (pgl) phenotype throughout the whole development as well as reduced grain quality. Map-based cloning of PGL3 revealed that it encodes the chloroplast signal recognition particle 43 kDa protein (cpSRP43). PGL3 affected the Chl synthesis by regulating the expression levels of the Chl synthesis-associated genes. Considerable reactive oxygen species were accumulated in the leaves of pgl3, and the transcription levels of its scavenging genes were down-regulated, indicating that pgl3 can accelerate senescence. In addition, high temperatures could inhibit the plant's growth and facilitate the process of senescence in pgl3.
Chlorophyll/metabolism* ; Chloroplasts/metabolism* ; Cloning, Molecular ; Gene Expression Regulation, Plant ; Genes, Plant ; Hot Temperature ; Mutation ; Oryza/physiology* ; Phenotype ; Photosynthesis ; Plant Leaves/metabolism* ; Plant Proteins/genetics* ; Reactive Oxygen Species/metabolism*