The CsHSFA-CsJAZ6 module-mediated high temperature regulates flavonoid metabolism in Camellia sinensis

Heat-induced modulation of flavonoid biosynthesis via a LhMYBC2-Mediated regulatory network in oriental hybrid lily

Global warming significantly threatens crop production, and adversely affects plant physiology due to rising temperatures. Oriental hybrid lily, an ornamental plant of economic importance, experiences flower color changes in response to elevated temperatures. Anthocyanins belong to a subgroup of flavonoids and are the primary pigments responsible for the coloration of oriental hybrid lily petals. However, the regulatory mechanisms governing flavonoid biosynthesis under high temperature conditions in lilies remain poorly understood. In this study, we revealed the altered metabolite profiles in flavonoid biosynthesis using quasi-targeted metabolomic and transcriptomic analyses. Isoflavonoids accumulate substantially under high temperature conditions, whereas the accumulation of anthocyanin decreases. The expression of the isoflavone reductase gene (LhIFR) and the transcription factor LhMYBC2 were upregulated in response to high temperatures. The LhMYBC2 protein, which belongs to Subgroup 4-AtMYB4, competes with the anthocyanin positive regulator LhMYBA1 for the LhTT8 partner, thereby repressing the formation of a positively regulated transcription complex. Heterologous overexpression of LhMYBC2 in tobacco led to reduced anthocyanin accumulation and increased isoflavonoid accumulation, corroborating its role in inhibiting anthocyanin biosynthesis. This study proposes a regulatory model wherein LhMYBC2 acts as a mediator of flavonoid biosynthesis, influencing the coloration of lily flowers under high-temperature stress. These findings deepen our understanding of the metabolic and transcriptional responses of lily to heat stress and underscore the potential role of LhMYBC2 in mitigating anthocyanin accumulation.

Comparative transcriptomic and metabolomic analyses provide insights into the responses to high temperature stress in Alfalfa (Medicago sativa L.)

High temperature stress is one of the most severe forms of abiotic stress in alfalfa. With the intensification of climate change, the frequency of high temperature stress will further increase in the future, which will bring challenges to the growth and development of alfalfa. Therefore, untargeted metabolomic and RNA-Seq profiling were implemented to unravel the possible alteration in alfalfa seedlings subjected to different temperature stress (25 ℃, 30 ℃, 35 ℃, 40 ℃) in this study. Results revealed that High temperature stress significantly altered some pivotal transcripts and metabolites. The number of differentially expressed genes (DEGs) markedly up and down-regulated was 1876 and 1524 in T30_vs_CK, 2, 815 and 2667 in T35_vs_CK, and 2115 and 2, 226 in T40_vs_CK, respectively. The number for significantly up-regulated and down-regulated differential metabolites was 173 and 73 in T30_vs_CK, 188 and 57 in T35_vs_CK, and 220 and 66 in T40_vs_CK, respectively. It is worth noting that metabolomics and transcriptomics co-analysis characterized enriched in plant hormone signal transduction (ko04705), glyoxylate and dicarboxylate metabolism (ko00630), from which some differentially expressed genes and differential metabolites participated. In particular, the content of hormone changed significantly under T40 stress, suggesting that maintaining normal hormone synthesis and metabolism may be an important way to improve the HTS tolerance of alfalfa. The qRT-PCR further showed that the expression pattern was similar to the expression abundance in the transcriptome. This study provides a practical and in-depth perspective from transcriptomics and metabolomics in investigating the effects conferred by temperature on plant growth and development, which provided the theoretical basis for breeding heat-resistant alfalfa.

CsPHRs-CsJAZ3 incorporates phosphate signaling and jasmonate pathway to regulate catechin biosynthesis in Camellia sinensis

Catechins constitute abundant metabolites in tea and have potential health benefits and high economic value. Intensive study has shown that the biosynthesis of tea catechins is regulated by environmental factors and hormonal signals. However, little is known about the coordination of phosphate (Pi) signaling and the jasmonic acid (JA) pathway on biosynthesis of tea catechins. We found that Pi deficiency caused changes in the content of catechins and modulated the expression levels of genes involved in catechin biosynthesis. Herein, we identified two transcription factors of phosphate signaling in tea, named CsPHR1 and CsPHR2, respectively. Both regulated catechin biosynthesis by activating the transcription of CsANR1 and CsMYB5c. We further demonstrated CsSPX1, a Pi pathway repressor, suppressing the activation by CsPHR1/2 of CsANR1 and CsMYB5c. JA, one of the endogenous plant hormones, has been reported to be involved in the regulation of secondary metabolism. Our work demonstrated that the JA signaling repressor CsJAZ3 negatively regulated catechin biosynthesis via physical interaction with CsPHR1 and CsPHR2. Thus, the CsPHRs-CsJAZ3 module bridges the nutrition and hormone signals, contributing to targeted cultivation of high-quality tea cultivars with high fertilizer efficiency.

Jasmonate enhances cold acclimation in jojoba by promoting flavonol synthesis

Jojoba is an industrial oil crop planted in tropical arid areas, and its low-temperature sensitivity prevents its introduction into temperate areas. Studying the molecular mechanisms associated with cold acclimation in jojoba is advantageous for developing breeds with enhanced cold tolerance. In this study, metabolomic analysis revealed that various flavonols accumulate in jojoba during cold acclimation. Time-course transcriptomic analysis and weighted correlation network analysis (WGCNA) demonstrated that flavonol biosynthesis and jasmonates (JAs) signaling pathways played crucial roles in cold acclimation. Combining the biochemical and genetic analyses showed that ScMYB12 directly activated flavonol synthase gene (ScFLS). The interaction between ScMYB12 and transparent testa 8 (ScTT8) promoted the expression of ScFLS, but the negative regulator ScJAZ13 in the JA signaling pathway interacted with ScTT8 to attenuate the transcriptional activity of the ScTT8 and ScMYB12 complex, leading to the downregulation of ScFLS. Cold acclimation stimulated the production of JA in jojoba leaves, promoted the degradation of ScJAZ13, and activated the transcriptional activity of ScTT8 and ScMYB12 complexes, leading to the accumulation of flavonols. Our findings reveal the molecular mechanism of JA-mediated flavonol biosynthesis during cold acclimation in jojoba and highlight the JA pathway as a promising means for enhancing cold tolerance in breeding efforts.

MaHsf24, a novel negative modulator, regulates cold tolerance in banana fruits by repressing the expression of HSPs and antioxidant enzyme genes

Transcriptional regulation mechanisms underlying chilling injury (CI) development have been widely investigated in model plants and cold-sensitive fruits, such as banana (Musa acuminata). However, unlike the well-known NAC and WRKY transcription factors (TFs), the function and deciphering mechanism of heat shock factors (HSFs) involving in cold response are still fragmented. Here, we showed that hot water treatment (HWT) alleviated CI in harvested banana fruits accomplishing with reduced reactive oxygen species (ROS) accumulation and increased antioxidant enzyme activities. A cold-inducible but HWT-inhibited HSF, MaHsf24, was identified. Using DNA affinity purification sequencing (DAP-seq) combined with RNA-seq analyses, we found three heat shock protein (HSP) genes (MaHSP23.6, MaHSP70-1.1 and MaHSP70-1.2) and three antioxidant enzyme genes (MaAPX1, MaMDAR4 and MaGSTZ1) were the potential targets of MaHsf24. Subsequent electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) and dual-luciferase reporter (DLR) analyses demonstrated that MaHsf24 repressed the transcription of these six targets via directly binding to their promoters. Moreover, stably overexpressing MaHsf24 in tomatoes increased cold sensitivity by suppressing the expressions of HSPs and antioxidant enzyme genes, while HWT could recover cold tolerance, maintaining higher levels of HSPs and antioxidant enzyme genes, and activities of antioxidant enzymes. In contrast, transiently silencing MaHsf24 by virus-induced gene silencing (VIGS) in banana peels conferred cold resistance with the upregulation of MaHSPs and antioxidant enzyme genes. Collectively, our findings support the negative role of MaHsf24 in cold tolerance, and unravel a novel regulatory network controlling bananas CI occurrence, concerning MaHsf24-exerted inhibition of MaHSPs and antioxidant enzyme genes.

Early signaling enhance heat tolerance in Arabidopsis through modulating jasmonic acid synthesis mediated by HSFA2

Given the detrimental impact of global warming on crop production, it is particularly important to understand how plants respond and adapt to higher temperatures. Using the non-invasive micro-test technique and laser confocal microscopy, we found that the cascade process of early signals (K+, H2O2, H+, and Ca2+) ultimately resulted in an increase in the cytoplasmic Ca2+ concentration when Arabidopsis was exposed to heat stress. Quantitative real-time PCR demonstrated that heat stress significantly up-regulated the expression of CAM1, CAM3 and HSFA2; however, after CAM1 and CAM3 mutation, the upregulation of HSFA2 was reduced. In addition, heat stress affected the expression of LOX3 and OPR3, which was not observed when HSFA2 was mutated. Luciferase reporter gene expression assay and electrophoretic mobility shift assay showed that HSFA2 regulated the expression of both genes. Determination of jasmonic acid (JA) content showed that JA synthesis was promoted by heat stress, but was damaged when HSFA2 and OPR3 were mutated. Finally, physiological experiments showed that JA reduced the relative electrical conductivity of leaves, enhanced chlorophyll content and relative water content, and improved the survival rate of Arabidopsis under heat stress. Together, our results reveal a new pathway for Arabidopsis to sense and transmit heat signals; HSFA2 is involved in the JA synthesis, which can act as a defensive compound improving Arabidopsis heat tolerance.

The OsBZR1-OsSPX1/2 module fine-tunes the growth-immunity trade-off in adaptation to phosphate availability in rice

The growth-promoting hormones brassinosteroids (BRs) and their key signaling component BZR1 play a vital role in balancing normal growth and defense reactions. Here, we discovered that BRs and OsBZR1 upregulated sakuranetin accumulation and conferred basal defense against Magnaporthe oryzae infection under normal conditions. Resource shortages, including phosphate (Pi) deficiency, potentially disrupt this growth-defense balance. OsSPX1 and OsSPX2 have been reported to sense Pi concentration and interact with the Pi signal mediator OsPHR2, thus regulating Pi starvation responses. In this study, we discovered that OsSPX1/2 interacts with OsBZR1 in both Pi-sufficient and Pi-deficient conditions, inhibiting BR-responsive genes. When Pi is sufficient, OsSPX1/2 is captured by OsPHR2, enabling most of OsBZR1 to promote plant growth and maintain basal resistance. In response to Pi starvation, more OsSPX1/2 is released from OsPHR2 to inhibit OsBZR1 activity, resulting in slower growth. Collectively, our study reveals that the OsBZR1-SPX1/2 module balances the plant growth-immunity trade-off in response to Pi availability.

Recent Progress Regarding Jasmonates in Tea Plants: Biosynthesis, Signaling, and Function in Stress Responses

Tea plants have to adapt to frequently challenging environments due to their sessile lifestyle and perennial evergreen nature. Jasmonates regulate not only tea plants' responses to biotic stresses, including herbivore attack and pathogen infection, but also tolerance to abiotic stresses, such as extreme weather conditions and osmotic stress. In this review, we summarize recent progress about jasmonaic acid (JA) biosynthesis and signaling pathways, as well as the underlying mechanisms mediated by jasmontes in tea plants in responses to biotic stresses and abiotic stresses. This review provides a reference for future research on the JA signaling pathway in terms of its regulation against various stresses of tea plants. Due to the lack of a genetic transformation system, the JA pathway of tea plants is still in the preliminary stages. It is necessary to perform further efforts to identify new components involved in the JA regulatory pathway through the combination of genetic and biochemical methods.

CsMYB67 participates in the flavonoid biosynthesis of summer tea leaves

Flavonoids are important compounds in tea leaves imparting bitter and astringent taste, which also play key roles in tea plants responding to environmental stress. Our previous study showed that the expression level of CsMYB67 was positively correlated with the accumulation of flavonoids in tea leaves as exposed to sunlight. Here, we newly reported the function of CsMYB67 in regulating flavonoid biosynthesis in tea leaves. CsMYB67 was localized in the nucleus and responded to temperature. The results of transient expression assays showed the co-transformation of CsMYB67 and CsTTG1 promoted the transcription of CsANS promoter in the tobacco system. CsTTG1 was bound to the promoter of CsANS based on the results of yeast one-hybrid (Y1H) and transient expression assays, while CsMYB67 enhanced the transcription of CsANS through protein interaction with CsTTG1 according to the results of yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC). Thus, CsMYB67-CsTTG1 module enhanced the anthocyanin biosynthesis through up-regulating the transcription of CsANS. Besides, CsMYB67 also enhanced the transcription of CsFLS and CsUFGT through forming transcription factor complexes. The function of CsMYB67 on flavonoid biosynthesis in tea leaves was validated by gene suppression assay. As CsMYB67 was suppressed, the transcriptional level of CsFLS was greatly reduced, leading to a significant increase in the contents of total catechins and total anthocyanidins. Hence, CsMYB67 plays an important role in regulating the downstream pathway of flavonoid biosynthesis in summer tea leaves.

Comprehensive Genomic Analysis of Trihelix Family in Tea Plant (Camellia sinensis) and Their Putative Roles in Osmotic Stress

In plants, Trihelix transcription factors are responsible for regulating growth, development, and reaction to various abiotic stresses. However, their functions in tea plants are not yet fully understood. This study identified a total of 40 complete Trihelix genes in the tea plant genome, which are classified into five clades: GT-1 (5 genes), GT-2 (8 genes), GTγ (2 genes), SH4 (7 genes), and SIP1 (18 genes). The same subfamily exhibits similar gene structures and functional domains. Chromosomal mapping analysis revealed that chromosome 2 has the most significant number of trihelix family members. Promoter analysis identified cis-acting elements in C. sinensis trihelix (CsTH), indicating their potential to respond to various phytohormones and stresses. The expression analysis of eight representative CsTH genes from four subfamilies showed that all CsTHs were expressed in more tissues, and three CsTHs were significantly induced under ABA, NaCl, and drought stress. This suggests that CsTHs plays an essential role in tea plant growth, development, and response to osmotic stress. Furthermore, yeast strains have preliminarily proven that CsTH28, CsTH36, and CsTH39 can confer salt and drought tolerance. Our study provides insights into the phylogenetic relationships and functions of the trihelix transcription factors in tea plants. It also presents new candidate genes for stress-tolerance breeding.

Artificial warming affects sugar signals and flavonoid accumulation to improve female willows' growth faster than males

Increasing global warming is severely affecting tree growth and development. However, research on the sex-specific responses of dioecious trees to warming is scarce. Here, male and female Salix paraplesia were selected for artificial warming (an increase of 4 °C relative to ambient temperature) to investigate the effects on morphological, physiological, biochemical and molecular responses. The results showed that warming significantly promoted the growth of female and male S. paraplesia, but females grew faster than males. Warming affected photosynthesis, chloroplast structures, peroxidase activity, proline, flavonoids, nonstructural carbohydrates (NSCs) and phenolic contents in both sexes. Interestingly, warming increased flavonoid accumulation in female roots and male leaves but inhibited it in female leaves and male roots. The transcriptome and proteome results indicated that differentially expressed genes and proteins were significantly enriched in sucrose and starch metabolism and flavonoid biosynthesis pathways. The integrative analysis of transcriptomic, proteomic, biochemical and physiological data revealed that warming changed the expression of SpAMY, SpBGL, SpEGLC and SpAGPase genes, resulting in the reduction of NSCs and starch and the activation of sugar signaling, particularly SpSnRK1s, in female roots and male leaves. These sugar signals subsequently altered the expression of SpHCTs, SpLAR and SpDFR in the flavonoid biosynthetic pathway, ultimately leading to the differential accumulation of flavonoids in female and male S. paraplesia. Therefore, warming causes sexually differential responses of S. paraplesia, with females performing better than males.

Exploring the Heat Shock Transcription Factor (HSF) Gene Family in Ginger: A Genome-Wide Investigation on Evolution, Expression Profiling, and Response to Developmental and Abiotic Stresses

Ginger is a valuable crop known for its nutritional, seasoning, and health benefits. However, abiotic stresses, such as high temperature and drought, can adversely affect its growth and development. Heat shock transcription factors (HSFs) have been recognized as crucial elements for enhancing heat and drought resistance in plants. Nevertheless, no previous study has investigated the HSF gene family in ginger. In this research, a total of 25 ZoHSF members were identified in the ginger genome, which were unevenly distributed across ten chromosomes. The ZoHSF members were divided into three groups (HSFA, HSFB, and HSFC) based on their gene structure, protein motifs, and phylogenetic relationships with Arabidopsis. Interestingly, we found more collinear gene pairs between ZoHSF and HSF genes from monocots, such as rice, wheat, and banana, than dicots like Arabidopsis thaliana. Additionally, we identified 12 ZoHSF genes that likely arose from duplication events. Promoter analysis revealed that the hormone response elements (MEJA-responsiveness and abscisic acid responsiveness) were dominant among the various cis-elements related to the abiotic stress response in ZoHSF promoters. Expression pattern analysis confirmed differential expression of ZoHSF members across different tissues, with most showing responsiveness to heat and drought stress. This study lays the foundation for further investigations into the functional role of ZoHSFs in regulating abiotic stress responses in ginger.

Application of Multi-Perspectives in Tea Breeding and the Main Directions

Tea plants are an economically important crop and conducting research on tea breeding contributes to enhancing the yield and quality of tea leaves as well as breeding traits that satisfy the requirements of the public. This study reviews the current status of tea plants germplasm resources and their utilization, which has provided genetic material for the application of multi-omics, including genomics and transcriptomics in breeding. Various molecular markers for breeding were designed based on multi-omics, and available approaches in the direction of high yield, quality and resistance in tea plants breeding are proposed. Additionally, future breeding of tea plants based on single-cellomics, pangenomics, plant-microbe interactions and epigenetics are proposed and provided as references. This study aims to provide inspiration and guidance for advancing the development of genetic breeding in tea plants, as well as providing implications for breeding research in other crops.