Abstract Resveratrol, a pharmaceutically significant stilbenoid accumulates in mulberry roots. To elucidate the molecular mechanism underlying this tissue-specific biosynthesis, we systematically analyzed the stilbene synthase (STS) gene family in mulberry. Our investigation revealed that nine out of ten MnSTS genes form tandem repeats in a single genomic cluster. Co-expression clustering and phylogenetic analysis implied that these genes undergo purifying selection, resulting in highly consistent co-expression patterns across tissues, with particularly specific high expression in roots and calli. Subsequent weighted gene co-expression network analysis (WGCNA) identified the transcription factor (TF) MnWRKY22 as a key regulatory candidate. Functional validation confirmed that MnWRKY22 is specifically expressed in roots and calli and directly binds to W-box elements in all MnSTS promoters, thereby activating their transcription. Suppression of MnWRKY22 expression significantly reduced both MnSTS transcript levels and resveratrol accumulation, while its overexpression enhanced MnSTS expression and resveratrol production. Notably, overexpression of MnWRKY22 in leaves ectopically activated otherwise silent MnSTSs, enabling de novo resveratrol synthesis. This study reveals the coordinated evolutionary characteristics of the MnSTS gene family and establishes MnWRKY22 as a unified regulator of tissue-specific resveratrol accumulation in mulberry. These findings provide a foundation for enhancing resveratrol production through metabolic engineering approaches.
Abstract DNA methylation is an important mechanism in plant development and environmental adaptation, yet how distinct methylation features contribute to transcriptional stability and regulatory flexibility in long-lived woody plants remains poorly understood. Here, we integrated DNA methylomes, transcriptomes, and chromatin accessibility profiles from two Camellia sinensis varieties to examine the regulatory characteristics and conservation of two specific methylation architectures: gene body methylation (gbM) and DNA methylation valleys (DMVs). We found that gbM genes showed distinctive gene structures, broad and relatively stable expression, and highly conserved methylation states between orthologs. gbM-gbM orthologs also showed evidence of stronger selective constraint in a sequence-length-dependent manner, consistent with a close relationship between gbM and stable transcription of housekeeping genes. In contrast, DMVs were highly hypomethylated regions associated with TE depletion and pronounced TF footprint signals, both of which were closely linked with methylation level, while DMV-associated genes were enriched for developmental and stress-responsive functions. Genome synteny analyses further revealed substantial conservation of DMV patterns and TF footprint profiles between tea varieties, indicating broad conservation of DMV-associated regulatory features across divergent genetic backgrounds. Together, these findings reveal two complementary epigenetic architectures in a woody perennial plant, with gbM preferentially associated with transcriptional robustness and DMVs with regulatory features linked to development and environmental responses.
Summary Apple anthracnose, caused by Colletotrichum gloeosporioides, severely threatens global apple production. Autotetraploid ‘Hanfu’ apples show stronger anthracnose resistance than diploids, but the underlying molecular mechanism remains unclear. This study identified a novel salicylic acid (SA)-regulated lignin biosynthesis signaling pathway that is closely associated with the enhanced resistance in autotetraploid ‘Hanfu’ apples. Autotetraploid apples accumulated higher endogenous SA levels, and the SA-responsive transcription factor MdTGA9 was markedly induced by both SA treatment and C. gloeosporioides infection. Mechanistically, MdTGA9 acts as a nuclear transcriptional activator to directly bind to the MdERF138 promoter and activate its expression. MdERF138 then transactivates the lignin biosynthetic gene MdHCT, thereby promoting lignin accumulation. Functional verification showed that MdTGA9 overexpression in apple calli, fruits and leaves significantly enhanced anthracnose resistance, and MdERF138 and MdHCT were confirmed as positive regulators of this resistance. Collectively, this study reveals a previously uncharacterized MdTGA9-MdERF138-MdHCT regulatory cascade that integrates SA signaling and lignin-based physical defense, which accounts for the enhanced disease resistance of autotetraploid apple. These findings provide valuable gene resources and a new molecular mechanism for disease-resistance breeding in apple.
Abstract Seasonal leaf coloration, driven by anthocyanin dynamics, is a crucial adaptive response to thermal environments, yet the underlying transcriptional mechanisms remain largely elusive. Here, we utilized the ornamental crabapple Malus ‘Fengwu’, which exhibits a striking red-to-green transition upon warming, to unravel the thermo-responsive regulatory network. Low temperature maintains red pigmentation and high antioxidant capacity, whereas warming leads to a rapid decline in anthocyanin content. We identified MfWRKY51 and MfLBD1 as crucial transcriptional repressors of anthocyanin biosynthesis, exhibiting elevated expression in green leaves and downregulation under low-temperature conditions. Genetic and biochemical analyses demonstrated that MfWRKY51 and MfLBD1 inhibit anthocyanin accumulation and reduce antioxidant capacity, whereas silencing either gene enhances anthocyanin accumulation and antioxidant capacity. Mechanistically, MfWRKY51 directly binds to the promoters of anthocyanin structural genes (MfDFR, MfANS, and MfUFGT), while MfLBD1 binds to the MfDFR promoter, collectively repressing their transcription. Furthermore, MfMYB1, strongly induced by low temperature and jasmonate (JA), acts as a central positive regulator that directly binds to the promoters of MfWRKY51 and MfLBD1 to repress their transcription. Reciprocally, MfWRKY51 directly suppresses MfMYB1 transcription, forming a mutual-repression feedback loop that functions as a temperature-sensitive switch. This regulatory module is functionally conserved between ornamental crabapple and cultivated apple, where low temperature promotes anthocyanin accumulation by repressing MdWRKY51 and MdLBD1 orthologues. Collectively, our findings reveal a conserved transcriptional network integrating temperature and JA signals to fine-tune anthocyanin metabolism, providing mechanistic insights into plant seasonal adaptation.
Drought-induced osmotic stress severely compromises crop yield productivity and threatens global food security. This study reports TabZIP12, a wheat bZIP transcription factor, in regulating osmotic stress tolerance. Under drought and abscisic acid (ABA) treatment, TabZIP12 expression was significantly upregulated with a dose- and time-dependent manner. Y-2H, BiFC, Co-IP, and In vitro pull-down assays confirmed a physical interaction between TabZIP12 and the kinase TaSnRK2.6. This kinase further interacted with the phosphatase TaPP2C50, which in turn interacted with the ABA receptor TaPYL1. These interactions suggest the TabZIP12-involved constitution of a synergistic signaling module (TaPYL1-TaPP2C50-TaSnRK2.6-TabZIP12). Transgene analyses revealed the essential functions of the signaling module members. Of which, TaPYL1, TaSnRK2.6, and TabZIP12 positively while TaPP2C50 negatively regulated drought tolerance, due to their roles in modulating key physiological processes associated with stomatal movement, osmolyte biosynthesis, root morphology, ABA biosynthesis, and reactive oxygen species (ROS) scavenging. TabZIP12 possessed an ability in binding with the promoters of critical stress-responsive genes, namely SLAC1 gene TaSLAC1-4, P5CS gene TaP5CS1, PIN-FORMed gene TaPIN3, NCED gene TaNCED3, and APX gene TaAPX6 and activated their activation. Transgenic validation confirmed these genes in positively modulating drought adaptation. Notably, in a wheat variety panel sharing contrasting drought response, the transcripts of TabZIP12 and its target genes correlated significantly with plant dry matter and yield under drought conditions. Haplotype analysis identified TabZIP12-Hap1 as a favorable allele associated with enhanced drought tolerance. Our findings elucidate novel mechanisms underlying the bZIP-mediated drought response and provide valuable genetic resources for breeding drought-resistant wheat varieties.
