The Plant Journal最新文献

Flavonoids, as vital secondary metabolites, improve grape (Vitis vinifera L.) berry quality and shape wine flavor. Characterized by intense ultraviolet radiation and large diurnal temperature shifts, the high-altitude regions of Southwest China are well-suited for growing late-ripening grapes like Cabernet Sauvignon. However, how altitude influences flavonoid composition and the molecular mechanisms governing these changes remains poorly understood. In this study, we combined transcriptomic analysis with flavonoid profiling to monitor grape berry skins at four key developmental stages (from green berry to harvest) under two typical altitude gradients. Of the genes related to flavonoids, VvbHLH88 was identified as a candidate transcription factor related to the biosynthesis of anthocyanins (a class of flavonoids) by comparing skins from grapes grown at high and low altitudes. Determination of the anthocyanin content in wounded tissues of VvbHLH88-overexpressing and -silenced grape revealed that VvbHLH88 was a positive regulator of anthocyanin biosynthesis. Transcriptome analysis of VvbHLH88-overexpressing healing tissues showed that the expression of anthocyanin synthesis branching enzyme genes was upregulated. In addition, VvbHLH88 directly bound to the promoter of the UDP-glucoflavone-3-O-glucosyltransferase (VvUFGT) gene and activated its transcriptional regulation of anthocyanin synthesis. Consequently, these results uncover specific molecular pathways and transcriptional networks through which high-altitude ecological factors modulate flavonoid metabolism in grape berries, advancing our theoretical understanding of how environmental cues influence metabolic regulation and fruit quality.

Mitochondrial protein import is indispensable for organelle biogenesis and function, and is powered by the evolutionarily conserved presequence translocase-associated motor (PAM) complex. In Arabidopsis thaliana, three paralogs: PAM18-1, PAM18-2, and PAM18-3 encode J-domain proteins homologous to yeast PAM18, which stimulates the ATPase activity of mitochondrial HSP70 (mtHSP70) during protein translocation. Here, we identify PAM18-3 as the most highly and ubiquitously expressed paralog and demonstrate its critical role in mitochondrial function and plant development. Genetic disruption of PAM18-3 caused severe vegetative and reproductive defects, including reduced root length, smaller rosette size with fewer leaves, decreased plant height, shorter siliques, reduced seed set, and increased seed abortion. These phenotypes were fully rescued in complemented lines expressing PAM18-3. Ultrastructural analyses revealed profound mitochondrial abnormalities in mutants, whereas chloroplast architecture remained unaffected. Functional assays showed reduced mitochondrial membrane potential and altered respiratory flux with a compensatory induction of the alternative oxidase (AOX) pathway. Transcript profiling revealed upregulation of AOX genes and multiple components of the mitochondrial TIM23 import apparatus and associated chaperones. Import assays demonstrated reduced mitochondrial accumulation of canonical TIM23 substrates, including IDH, ATPβ, and SHMT1, confirming a defect in matrix protein translocation. Consistently, pam18-3 mutants accumulated elevated reactive oxygen species (ROS) and exhibited strong induction of mitochondrial dysfunction stimulon (MDS) genes, including key transcription factors mediating retrograde signaling. Together, our findings establish PAM18-3 as a central component of the mitochondrial protein import machinery, supporting plant growth and development in A. thaliana.

Pattern-triggered immunity (PTI) is the first layer of the plant immune system, which relies on the perception of pathogen-associated molecular patterns. Recently, it has been found that double-stranded RNA (dsRNA), a hallmark of viral invasion, triggers typical PTI responses; however, the underlying signaling pathways are not yet elucidated. Here, we identify a plant-specific, leucine-rich repeat family protein, AtCERES, involved in dsRNA-triggered activation of defense-related genes, MPK3/6 phosphorylation and seedling growth inhibition. AtCERES directly binds the mitochondrial glycoprotein AtXIAN, which also positively regulates dsRNA-triggered immune responses. Upon dsRNA perception, AtXIAN and AtCERES affect the level of mitochondrial reactive oxygen species (mROS), which is independent of respiratory burst oxygenase homologs D. Importantly, the generation of mROS is required for immune responses triggered by dsRNA. Together, our results uncover the function of AtCERES and AtXIAN as components of the dsRNA-triggered immune pathway, and suggest a link between mROS and antiviral immunity in plants.

Coumarins are structurally diverse phenylpropanoid derivatives with ecological and pharmacological significance, yet the biosynthetic logic underlying their diversification remains incompletely understood in non-model medicinal plants. Angelica pubescens (Apiaceae), widely used in traditional Chinese medicine, accumulates a rich repertoire of furanocoumarins and dihydrofuranocoumarins, making it an ideal system to investigate this metabolic complexity. Here, we combined chromosome-level genome assembly, transcriptome and metabolite profiling, phylogenetics, and heterologous expression assays to dissect coumarin biosynthesis in A. pubescens. We identified two functionally specialized O-methyltransferases, ApOMT1 and ApOMT2, which catalyze regioselective methylation of xanthotoxol and bergaptol to yield the furanocoumarins xanthotoxin and bergapten. We also characterized ApCYP736A121, a cytochrome P450 enzyme that converts osthenol to the dihydrofuranocoumarin columbianetin via a previously unknown mechanism. Gene expression and metabolite accumulation patterns across tissues and developmental stages revealed functional partitioning among pathway branches. Phylogenetic and syntenic analyses indicated that ApOMT1 and ApOMT2 arose through subfunctionalization following gene duplication, whereas ApCYP736A121 evolved via neofunctionalization from a distantly related CYP736 ancestor. Together, our findings uncover dual biosynthetic routes to structurally distinct coumarins in A. pubescens and provide insights into the evolutionary mechanisms contributing to metabolic innovation in Apiaceae. This work lays a foundation for future efforts to engineer coumarin pathways and understand their ecological functions in medicinal plants.

Cytokinins regulate diverse aspects of plant development. They are perceived by membrane-localised receptors that transmit a signal to nuclear-localised response regulators via the Histidine Phosphotransfer proteins (HPts). These HPts can be divided into two classes: authentic HPts (AHPs), which positively regulate cytokinin signalling, and pseudo HPts (PHPs), which inhibit it. Whilst four of the five Arabidopsis AHPs form a well-conserved monophyletic clade, AHP4 evolved separately and is more closely related to the monocot PHPs than to the dicot AHPs. AHP4's role in cytokinin signalling has been ambiguous; in some cases, it has been shown to act as a positive regulator, whilst in others, it acts negatively. Here, we propose that AHP4 act like a dimmer switch to dampen cytokinin output. Under optimal growth conditions, AHP4 is expressed at a low level in the phloem companion cells and has little effect on either cytokinin signalling or plant development. However, AHP4 expression is induced under osmotic stress, and under this condition, we show a novel role for AHP4 in reducing cytokinin signalling in the phloem and maintaining primary root growth. We propose that AHP4 fine-tunes responses to the osmotic environment by attenuating cytokinin signalling.

Drought poses a significant threat to global rice production, and a comparative study between rice and wheat serves as an essential approach to unravel the mechanisms relating to drought tolerance. This study examined the differential responses of gas exchange, leaf hydraulic conductance, and leaf morpho-anatomical traits in Shanyou 63 (Oryza sativa) and Yannong 19 (Triticum aestivum). Our findings revealed that rice photosynthesis was more sensitive to drought than wheat, primarily due to greater reductions in stomatal conductance (g_s) and mesophyll conductance (g_m). The larger reduction of g_s in rice was related to a more substantial decrease in leaf hydraulic conductance, which was driven by more severe downsizing of leaf xylem conduits and the thickened mestome cell walls. The more severe depression of g_m in rice under drought was associated with the decreased chloroplast surface area exposed to intercellular airspaces and cell wall porosity (φ/τ) as well as the thickened mesophyll cell walls (T_cw-mes). The thicker T_cw-mes and the decreased φ/τ may be related to the biosynthesis and deposition of cellulose and hemicellulose. This study provides evidence that the regulation of cell wall components and the retention of leaf morphological and anatomical structures play a critical role in maintaining a high photosynthetic capacity under drought stress.

High molecular weight glutenin subunits (HMW-GSs) are critical grain storage proteins in wheat, which govern its unique processing quality. A HMW-GS 1Dy10 allele variant (1Dy10-m619SN), carrying a serine-to-asparagine substitution at the 619th residue, undergoes partial posttranslational cleavage. This modification leads to improved cookie-making quality. However, the enzymes mediating this cleavage remain unknown. In this study, we identified vacuolar processing enzymes (VPEs) as candidates for 1Dy10-m619SN processing using TurboID-based proximity labeling and RNA-seq analysis. In vitro cleavage assays confirmed that VPEs catalyzed 1Dy10-m619SN cleavage. Phylogenic analysis revealed that there are two seed-type VPEs in wheat, TaVPEI and TaVPEII, with TaVPEI being further subdivided into TaVPEI-1, TaVPEI-2, and TaVPEI-3. Despite sharing conserved catalytic domains, these isoforms display distinct temporal expression patterns, with TaVPEI-1 expression showing the strongest correlation with the posttranslational cleavage of 1Dy10-m619SN. TaVPEI-1 protein is localized to the vacuole, the well-known deposition site for HMW-GSs. Overexpression of TaVPEI-1 in wheat enhances the 1Dy10-m619SN cleavage. Collectively, these findings demonstrate that the seed-type VPEs in wheat are responsible for the posttranslational cleavage of 1Dy10-m619SN, which provides new insights into the molecular basis of wheat's unique processing quality.

Bread wheat (Triticum aestivum L.) is an allohexaploid (AABBDD) whose three ancestral subgenomes generate complex patterns of gene regulation. Most genes exist as homoeologous triads, and the relative expression balance among copies, homoeolog expression bias, is central to polyploid evolution and adaptation. Recent high-quality assemblies, long-read transcriptomics, and pan-transcriptome resources have uncovered extensive cultivar-specific transcriptional diversity. Because transposable elements (TEs) compose over 80% of the wheat genome, they are prime candidates for shaping subgenome asymmetry. We synthesize recent pan-genomic and transcriptomic evidence, including genome-wide associations between TE insertions and genome-specific expression, and propose a unifying framework in which TEs modulate homoeolog expression by donating cis-regulatory sequences, altering chromatin states, producing small RNAs, and driving structural variation. We discuss experimental and computational challenges for establishing causality, and outline future functional and translational strategies to leverage TE-associated regulatory diversity in wheat breeding.