Rice copine genes OsBON1 and OsBON3 function as suppressors of broad-spectrum disease resistance

Antagonistic control of rice immunity against distinct pathogens by the two transcription modules via salicylic acid and jasmonic acid pathways

Although the antagonistic effects of host resistance against biotrophic and necrotrophic pathogens have been documented in various plants, the underlying mechanisms are unknown. Here, we investigated the antagonistic resistance mediated by the transcription factor ETHYLENE-INSENSITIVE3-LIKE 3 (OsEIL3) in rice. The Oseil3 mutant confers enhanced resistance to the necrotroph Rhizoctonia solani but greater susceptibility to the hemibiotroph Magnaporthe oryzae and biotroph Xanthomonas oryzae pv. oryzae. OsEIL3 directly activates OsERF040 transcription while repressing OsWRKY28 transcription. The infection of R. solani and M. oryzae or Xoo influences the extent of binding of OsEIL3 to OsWRKY28 and OsERF040 promoters, resulting in the repression or activation of both salicylic acid (SA)- and jasmonic acid (JA)-dependent pathways and enhanced susceptibility or resistance, respectively. These results demonstrate that the distinct effects of plant immunity to different pathogen types are determined by two transcription factor modules that control transcriptional reprogramming and the SA and JA pathways.

Copine proteins are required for brassinosteroid signaling in maize and Arabidopsis

Copine proteins are highly conserved and ubiquitously found in eukaryotes, and their indispensable roles in different species were proposed. However, their exact function remains unclear. The phytohormone brassinosteroids (BRs) play vital roles in plant growth, development and environmental responses. A key event in effective BR signaling is the formation of functional BRI1-SERK receptor complex and subsequent transphosphorylation upon ligand binding. Here, we demonstrate that BONZAI (BON) proteins, which are plasma membrane-associated copine proteins, are critical components of BR signaling in both the monocot maize and the dicot Arabidopsis. Biochemical and molecular analyses reveal that BON proteins directly interact with SERK kinases, thereby ensuring effective BRI1-SERK interaction and transphosphorylation. This study advances the knowledge on BR signaling and provides an important target for optimizing valuable agronomic traits, it also opens a way to study steroid hormone signaling and copine proteins of eukaryotes in a broader perspective.

How plants sense and respond to osmotic stress

Drought is one of the most serious abiotic stresses to land plants. Plants sense and respond to drought stress to survive under water deficiency. Scientists have studied how plants sense drought stress, or osmotic stress caused by drought, ever since Charles Darwin, and gradually obtained clues about osmotic stress sensing and signaling in plants. Osmotic stress is a physical stimulus that triggers many physiological changes at the cellular level, including changes in turgor, cell wall stiffness and integrity, membrane tension, and cell fluid volume, and plants may sense some of these stimuli and trigger downstream responses. In this review, we emphasized water potential and movements in organisms, compared putative signal inputs in cell wall-containing and cell wall-free organisms, prospected how plants sense changes in turgor, membrane tension, and cell fluid volume under osmotic stress according to advances in plants, animals, yeasts, and bacteria, summarized multilevel biochemical and physiological signal outputs, such as plasma membrane nanodomain formation, membrane water permeability, root hydrotropism, root halotropism, Casparian strip and suberin lamellae, and finally proposed a hypothesis that osmotic stress responses are likely to be a cocktail of signaling mediated by multiple osmosensors. We also discussed the core scientific questions, provided perspective about the future directions in this field, and highlighted the importance of robust and smart root systems and efficient source-sink allocations for generating future high-yield stress-resistant crops and plants.

OsJAZ4 Fine-Tunes Rice Blast Resistance and Yield Traits

JAZ proteins function as transcriptional regulators that form a jasmonic acid-isoleucine (JA-Ile) receptor complex with coronatine insensitive 1 (COI1) and regulate plant growth and development. These proteins also act as key mediators in signal transduction pathways that activate the defense-related genes. Herein, the role of OsJAZ4 in rice blast resistance, a severe disease, was examined. The mutation of OsJAZ4 revealed its significance in Magnaporthe oryzae (M. oryzae) resistance and the seed setting rate in rice. In addition, weaker M. oryzae-induced ROS production and expression of the defense genes OsO4g10010, OsWRKY45, OsNAC4, and OsPR3 was observed in osjaz4 compared to Nipponbare (NPB); also, the jasmonic acid (JA) and gibberellin4 (GA4) content was significantly lower in osjaz4 than in NPB. Moreover, osjaz4 exhibited a phenotype featuring a reduced seed setting rate. These observations highlight the involvement of OsJAZ4 in the regulation of JA and GA4 content, playing a positive role in regulating the rice blast resistance and seed setting rate.

The OsSGS3-tasiRNA-OsARF3 module orchestrates abiotic-biotic stress response trade-off in rice

Recurrent heat stress and pathogen invasion seriously threaten crop production, and abiotic stress often antagonizes biotic stress response against pathogens. However, the molecular mechanisms of trade-offs between thermotolerance and defense remain obscure. Here, we identify a rice thermo-sensitive mutant that displays a defect in floret development under high temperature with a mutation in SUPPRESSOR OF GENE SILENCING 3a (OsSGS3a). OsSGS3a interacts with its homolog OsSGS3b and modulates the biogenesis of trans-acting small interfering RNA (tasiRNA) targeting AUXIN RESPONSE FACTORS (ARFs). We find that OsSGS3a/b positively, while OsARF3a/b and OsARF3la/lb negatively modulate thermotolerance. Moreover, OsSGS3a negatively, while OsARF3a/b and OsARF3la/lb positively regulate disease resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) and the fungal pathogen Magnaporthe oryzae (M. oryzae). Taken together, our study uncovers a previously unknown trade-off mechanism that regulates distinct immunity and thermotolerance through the OsSGS3-tasiRNA-OsARF3 module, highlighting the regulation of abiotic-biotic stress response trade-off in plants.

An unusual tandem kinase fusion protein confers leaf rust resistance in wheat

The introgression of chromosome segments from wild relatives is an established strategy to enrich crop germplasm with disease-resistance genes¹. Here we use mutagenesis and transcriptome sequencing to clone the leaf rust resistance gene Lr9, which was introduced into bread wheat from the wild grass species Aegilops umbellulata². We established that Lr9 encodes an unusual tandem kinase fusion protein. Long-read sequencing of a wheat Lr9 introgression line and the putative Ae. umbellulata Lr9 donor enabled us to assemble the ~28.4-Mb Lr9 translocation and to identify the translocation breakpoint. We likewise cloned Lr58, which was reportedly introgressed from Aegilops triuncialis³, but has an identical coding sequence compared to Lr9. Cytogenetic and haplotype analyses corroborate that the two genes originate from the same translocation event. Our work sheds light on the emerging role of kinase fusion proteins in wheat disease resistance, expanding the repertoire of disease-resistance genes for breeding.

A natural allele of proteasome maturation factor improves rice resistance to multiple pathogens

Crops with broad-spectrum resistance loci are highly desirable in agricultural production because these loci often confer resistance to most races of a pathogen or multiple pathogen species. Here we discover a natural allele of proteasome maturation factor in rice, UMP1^R2115, that confers broad-spectrum resistance to Magnaporthe oryzae, Rhizoctonia solani, Ustilaginoidea virens and Xanthomonas oryzae pv. oryzae. Mechanistically, this allele increases proteasome abundance and activity to promote the degradation of reactive oxygen species-scavenging enzymes including peroxidase and catalase upon pathogen infection, leading to elevation of H₂O₂ accumulation for defence. In contrast, inhibition of proteasome function or overexpression of peroxidase/catalase-encoding genes compromises UMP1^R2115-mediated resistance. More importantly, introduction of UMP1^R2115 into a disease-susceptible rice variety does not penalize grain yield while promoting disease resistance. Our work thus uncovers a broad-spectrum resistance pathway integrating de-repression of plant immunity and provides a valuable genetic resource for breeding high-yield rice with multi-disease resistance.

Cytological observation and transcriptome analysis reveal dynamic changes of Rhizoctonia solani colonization on leaf sheath and different genes recruited between the resistant and susceptible genotypes in rice

Sheath blight, caused by Rhizoctonia solani, is a big threat to the global rice production. To characterize the early development of R. solani on rice leaf and leaf sheath, two genotypes, GD66 (a resistant genotype) and Lemont (a susceptible genotype), were observed using four cytological techniques: the whole-mount eosin B-staining confocal laser scanning microscopy (WE-CLSM), stereoscopy, fluorescence microscopy, and plastic semi-thin sectioning after in vitro inoculation. WE-CLSM observation showed that, at 12 h post-inoculation (hpi), the amount of hyphae increased dramatically on leaf and sheath surface, the infection cushions occurred and maintained at a huge number from about 18 to 36 hpi, and then the infection cushions disappeared gradually from about 42 to 72 hpi. Interestingly, R. solani could not only colonize on the abaxial surfaces of leaf sheath but also invade the paraxial side of the leaf sheath, which shows a different behavior from that of leaf. RNA sequencing detected 6,234 differentially expressed genes (DEGs) for Lemont and 7,784 DEGs for GD66 at 24 hpi, and 2,523 DEGs for Lemont and 2,719 DEGs for GD66 at 48 hpi, suggesting that GD66 is recruiting more genes in fighting against the pathogen. Among DEGs, resistant genes, such as OsRLCK5, Xa21, and Pid2, displayed higher expression in the resistant genotype than the susceptible genotype at both 24 and 48 hpi, which were validated by quantitative reverse transcription-PCR. Our results indicated that the resistance phenotype of GD66 was the consequence of recruiting a series of resistance genes involved in different regulatory pathways. WE-CLSM is a powerful technique for uncovering the mechanism of R. solani invading rice and for detecting rice sheath blight-resistant germplasm.

Evaluation of rice bacterial blight severity from lab to field with hyperspectral imaging technique

Hyperspectral imaging technique combined with machine learning is a powerful tool for the evaluation of disease phenotype in rice disease-resistant breeding. However, the current studies are almost carried out in the lab environment, which is difficult to apply to the field environment. In this paper, we used visible/near-infrared hyperspectral images to analysis the severity of rice bacterial blight (BB) and proposed a novel disease index construction strategy (NDSCI) for field application. A designed long short-term memory network with attention mechanism could evaluate the BB severity robustly, and the attention block could filter important wavelengths. Best results were obtained based on the fusion of important wavelengths and color features with an accuracy of 0.94. Then, NSDCI was constructed based on the important wavelength and color feature related to BB severity. The correlation coefficient of NDSCI extended to the field data reached -0.84, showing good scalability. This work overcomes the limitations of environmental conditions and sheds new light on the rapid measurement of phenotype in disease-resistant breeding.

Rice (Oryza sativa L.) cytochrome P450 protein 716A subfamily CYP716A16 regulates disease resistance

Background

The sustainable development of rice production is facing severe threats by a variety of pathogens, such as necrotrophic Rhizoctonia solani and hemibiotrophic Xanthomonas oryzae pv. oryzae (Xoo). Mining and applying resistance genes to increase the durable resistance of rice is an effective method that can be used to control these diseases.

Results

In this research, we isolated and characterized CYP716A16, which is a positive regulator of rice to R. solani AG1-IA and Xoo, and belongs to the cytochrome P450 (CYP450) protein 716A subfamily. Overexpression (OE) of CYP716A16 resulted in enhanced resistance to R. solani AG1-IA and Xoo, while RNA interference (RNAi) of CYP716A16 resulted in increased susceptibility compared with wild-type (WT) plants. Additionally, jasmonic acid (JA)-dependent defense responses and reactive oxygen species (ROS) were activated in the CYP716A16-OE lines after R. solani AG1-IA inoculation. The comparative transcriptomic and metabolomics analysis of CYP716A16-OE and the WT lines showed that OE of CYP716A16 activated the biosynthesis of flavonoids and increased the amounts of narcissoside, methylophiopogonanone A, oroxin A, and amentoflavone in plants.

Conclusion

Based on these results, we suggest that JA-dependent response, ROS level, multiple resistance-related proteins, and flavonoid contents play an important role in CYP716A16-regulated R. solani AG1-IA and Xoo resistance. Our results broaden our knowledge regarding the function of a P450 protein 716A subfamily in disease resistance and provide new insight into the molecular mechanism of rice immune response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08568-8.

Engineering of rice varieties with enhanced resistances to both blast and bacterial blight diseases via CRISPR/Cas9

Rice blast and bacterial blight represent two of major diseases having devastating impact on the yield of rice in most rice-growing countries. Developments of resistant cultivars are the most economic and effective strategy to control these diseases. Here, we used CRISPR/Cas9-mediated gene editing to rapidly install mutations in three known broad-spectrum blast-resistant genes, Bsr-d1, Pi21 and ERF922, in an indica thermosensitive genic male sterile (TGMS) rice line Longke638S (LK638S). We obtained transgene-free homozygous single or triple mutants in T₁ generations. While all single and triple mutants showed increased resistance to rice blast compared with wild type, the erf922 mutants displayed the strongest blast resistance similar with triple mutants. Surprisingly, we found that Pi21 or ERF922 single mutants conferred enhanced resistance to most of tested bacterial blight. Both resistances in mutants were attribute to the up-regulation of SA- and JA-pathway associated genes. Moreover, phenotypic analysis of these single mutants in paddy fields revealed that there were no trade-offs between resistances and main agricultural traits. Together, our study provides a rapid and effective way to generate rice varieties with resistance to both rice blast and bacterial blight.

OsTGAL1 suppresses the resistance of rice to bacterial blight disease by regulating the expression of salicylic acid glucosyltransferase OsSGT1

Many TGA transcription factors participate in immune responses in the SA-mediated signaling pathway in Arabidopsis. This study identified a transcription factor OsTGAL1, which is induced upon infection by Xoo. Overexpression of OsTGAL1 increased the susceptibility of rice to Xoo. Plants overexpressing OsTGAL1 could affect the expression of many SA signaling-related genes. OsTGAL1 was able to interact with the promoter of OsSGT1, which encodes a key enzyme for SA metabolism. The transcript of OsSGT1 was induced by Xoo and this responsive expression was further increased in plants overexpressing OsTGAL1. OsSGT1 knockout lines had enhanced resistance to Xoo, and knocking out OsSGT1 in plants overexpressing OsTGAL1 blocked the susceptibility caused by OsTGAL1. Altered expression levels of several OsPRs in all the transgenic plants demonstrated that SA-mediated signaling had been affected. Furthermore, we identified an oxidoreductase of CC-type glutaredoxin, OsGRX17, which interacted with OsTGAL1. OsGRX17 reduced the regulation of OsTGAL1 on OsSGT1, and this may be due to its redox modulation. Thus, our results demonstrate that OsTGAL1 negatively regulates resistance to Xoo by its effects on SA metabolism via the activation of OsSGT1, which provides valuable targets for plant breeders in developing new cultivars that are resistant to Xoo.

An MKP-MAPK protein phosphorylation cascade controls vascular immunity in plants

Global crop production is greatly reduced by vascular diseases. These diseases include bacterial blight of rice and crucifer black rot caused by Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas campestris pv. campestris (Xcc). The molecular mechanisms that activate vascular defense against such pathogens remains underexplored. Here, we show that an Arabidopsis MAPK phosphatase 1 (MKP1) mutant has increased host susceptibility to the adapted pathogen Xcc and is compromised in nonhost resistance to the rice pathogen Xoo. MKP1 regulates MAPK-mediated phosphorylation of the transcription factor MYB4 that negatively regulates vascular lignification through inhibiting lignin biosynthesis. Induction of lignin biosynthesis is, therefore, an important part of vascular-specific immunity. The role of MKP-MAPK-MYB signaling in lignin biosynthesis and vascular resistance to Xoo is conserved in rice, indicating that these factors form a tissue-specific defense regulatory network. Our study likely reveals a major vascular immune mechanism that underlies tissue-specific disease resistance against bacterial pathogens in plants.

SDR7-6, a short-chain alcohol dehydrogenase/reductase family protein, regulates light-dependent cell death and defence responses in rice

Lesion mimic mutants resembling the hypersensitive response without pathogen attack are an ideal material to understand programmed cell death, the defence response, and the cross-talk between defence response and development in plants. In this study, mic, a lesion mimic mutant from cultivar Yunyin treated with ethyl methanesulphonate (EMS), was screened. By map-based cloning, a short-chain alcohol dehydrogenase/reductase with an atypical active site HxxxK was isolated and designated as SDR7-6. It functions as a homomultimer in rice and is localized at the endoplasmic reticulum. The lesion mimic phenotype of the mutant is light-dependent. The mutant displayed an increased resistance response to bacterial blight, but reduced resistance to rice blast disease. The mutant and knockout lines showed increased reactive oxygen species, jasmonic acid content, antioxidant enzyme activity, and expression of pathogenicity-related genes, while chlorophyll content was significantly reduced. The knockout lines showed significant reduction in grain size, seed setting rate, 1000-grain weight, grain weight per plant, panicle length, and plant height. SDR7-6 is a new lesion mimic gene that encodes a short-chain alcohol dehydrogenase with atypical catalytic site. Disruption of SDR7-6 led to cell death and had adverse effects on multiple agricultural characters. SDR7-6 may act at the interface of the two defence pathways of bacterial blight and rice blast disease in rice.

Recent Progress in Rice Broad-Spectrum Disease Resistance

Rice is one of the most important food crops in the world. However, stable rice production is constrained by various diseases, in particular rice blast, sheath blight, bacterial blight, and virus diseases. Breeding and cultivation of resistant rice varieties is the most effective method to control the infection of pathogens. Exploitation and utilization of the genetic determinants of broad-spectrum resistance represent a desired way to improve the resistance of susceptible rice varieties. Recently, researchers have focused on the identification of rice broad-spectrum disease resistance genes, which include R genes, defense-regulator genes, and quantitative trait loci (QTL) against two or more pathogen species or many isolates of the same pathogen species. The cloning of broad-spectrum disease resistance genes and understanding their underlying mechanisms not only provide new genetic resources for breeding broad-spectrum rice varieties, but also promote the development of new disease resistance breeding strategies, such as editing susceptibility and executor R genes. In this review, the most recent advances in the identification of broad-spectrum disease resistance genes in rice and their application in crop improvement through biotechnology approaches during the past 10 years are summarized.

Ca2+ sensor-mediated ROS scavenging suppresses rice immunity and is exploited by a fungal effector

Plant immunity is activated upon pathogen perception and often affects growth and yield when it is constitutively active. How plants fine-tune immune homeostasis in their natural habitats remains elusive. Here, we discover a conserved immune suppression network in cereals that orchestrates immune homeostasis, centering on a Ca²⁺-sensor, RESISTANCE OF RICE TO DISEASES1 (ROD1). ROD1 promotes reactive oxygen species (ROS) scavenging by stimulating catalase activity, and its protein stability is regulated by ubiquitination. ROD1 disruption confers resistance to multiple pathogens, whereas a natural ROD1 allele prevalent in indica rice with agroecology-specific distribution enhances resistance without yield penalty. The fungal effector AvrPiz-t structurally mimics ROD1 and activates the same ROS-scavenging cascade to suppress host immunity and promote virulence. We thus reveal a molecular framework adopted by both host and pathogen that integrates Ca²⁺ sensing and ROS homeostasis to suppress plant immunity, suggesting a principle for breeding disease-resistant, high-yield crops.

Comparative transcriptomic analysis highlights contrasting levels of resistance of Vitis vinifera and Vitis amurensis to Botrytis cinerea

Botrytis cinerea is a major grapevine (Vitis spp.) pathogen, but some genotypes differ in their degree of resistance. For example, the Vitis vinifera cultivar Red Globe (RG) is highly susceptible, but V. amurensis Rupr Shuangyou (SY) is highly resistant. Here, we used RNA sequencing analysis to characterize the transcriptome responses of these two genotypes to B. cinerea inoculation at an early infection stage. Approximately a quarter of the genes in RG presented significant changes in transcript levels during infection, the number of which was greater than that in the SY leaves. The genes differentially expressed between infected leaves of SY and RG included those associated with cell surface structure, oxidation, cell death and C/N metabolism. We found evidence that an imbalance in the levels of reactive oxygen species (ROS) and redox homeostasis probably contributed to the susceptibility of RG to B. cinerea. SY leaves had strong antioxidant capacities and improved ROS homeostasis following infection. Regulatory network prediction suggested that WRKY and MYB transcription factors are associated with the abscisic acid pathway. Weighted gene correlation network analysis highlighted preinfection features of SY that might contribute to its increased resistance. Moreover, overexpression of VaWRKY10 in Arabidopsis thaliana and V. vinifera Thompson Seedless enhanced resistance to B. cinerea. Collectively, our study provides a high-resolution view of the transcriptional changes of grapevine in response to B. cinerea infection and novel insights into the underlying resistance mechanisms.

Strategies to Manage Rice Sheath Blight: Lessons from Interactions between Rice and Rhizoctonia solani

Rhizoctonia solani is an important phytopathogenic fungus with a wide host range and worldwide distribution. The anastomosis group AG1 IA of R. solani has been identified as the predominant causal agent of rice sheath blight, one of the most devastating diseases of crop plants. As a necrotrophic pathogen, R. solani exhibits many characteristics different from biotrophic and hemi-biotrophic pathogens during co-evolutionary interaction with host plants. Various types of secondary metabolites, carbohydrate-active enzymes, secreted proteins and effectors have been revealed to be essential pathogenicity factors in R. solani. Meanwhile, reactive oxygen species, phytohormone signaling, transcription factors and many other defense-associated genes have been identified to contribute to sheath blight resistance in rice. Here, we summarize the recent advances in studies on molecular interactions between rice and R. solani. Based on knowledge of rice-R. solani interactions and sheath blight resistance QTLs, multiple effective strategies have been developed to generate rice cultivars with enhanced sheath blight resistance.

BONZAI Proteins Control Global Osmotic Stress Responses in Plants

Hyperosmotic stress caused by drought and salinity is a significant environmental threat that limits plant growth and agricultural productivity. Osmotic stress induces diverse responses in plants including Ca²⁺ signaling, accumulation of the stress hormone abscisic acid (ABA), reprogramming of gene expression, and altering of growth. Despite intensive investigation, no global regulators of all of these responses have been identified. Here, we show that the Ca²⁺-responsive phospholipid-binding BONZAI (BON) proteins are critical for all of these osmotic stress responses. A Ca²⁺-imaging-based forward genetic screen identified a loss-of-function bon1 mutant with a reduced cytosolic Ca²⁺ signal in response to hyperosmotic stress. The loss-of-function mutants of the BON1 gene family, bon1bon2bon3, are impaired in the induction of gene expression and ABA accumulation in response to osmotic stress. In addition, the bon mutants are hypersensitive to osmotic stress in growth inhibition. BON genes have been shown to negatively regulate plant immune responses mediated by intracellular immune receptor NLR genes including SNC1. We found that the defects of the bon mutants in osmotic stress responses were suppressed by mutations in the NLR gene SNC1 or the immunity regulator PAD4. Our findings indicate that NLR signaling represses osmotic stress responses and that BON proteins suppress NLR signaling to enable global osmotic stress responses in plants.

Molecular Basis of Disease Resistance and Perspectives on Breeding Strategies for Resistance Improvement in Crops

Crop diseases are major factors responsible for substantial yield losses worldwide, which affects global food security. The use of resistance (R) genes is an effective and sustainable approach to controlling crop diseases. Here, we review recent advances on R gene studies in the major crops and related wild species. Current understanding of the molecular mechanisms underlying R gene activation and signaling, and susceptibility (S) gene-mediated resistance in crops are summarized and discussed. Furthermore, we propose some new strategies for R gene discovery, how to balance resistance and yield, and how to generate crops with broad-spectrum disease resistance. With the rapid development of new genome-editing technologies and the availability of increasing crop genome sequences, the goal of breeding next-generation crops with durable resistance to pathogens is achievable, and will be a key step toward increasing crop production in a sustainable way.

The crystal structure of Arabidopsis BON1 provides insights into the copine protein family

The Arabidopsis thaliana BON1 gene product is a member of the evolutionary conserved eukaryotic calcium-dependent membrane-binding protein family. The copine protein is composed of two C2 domains (C2A and C2B) followed by a vWA domain. The BON1 protein is localized on the plasma membrane, and is known to suppress the expression of immune receptor genes and to positively regulate stomatal closure. The first structure of this protein family has been determined to 2.5-Å resolution and shows the structural features of the three conserved domains C2A, C2B and vWA. The structure reveals the third Ca²⁺ -binding region in C2A domain is longer than classical C2 domains and a novel Ca²⁺ binding site in the vWA domain. The structure of BON1 bound to Mn²⁺ is also presented. The binding of the C2 domains to phospholipid (PSF) has been modeled and provides an insight into the lipid-binding mechanism of the copine proteins. Furthermore, the selectivity of the separate C2A and C2B domains and intact BON1 to bind to different phospholipids has been investigated, and we demonstrated that BON1 could mediate aggregation of liposomes in response to Ca²⁺ . These studies have formed the basis of further investigations into the important role that the copine proteins play in vivo.

The VvBAP1 gene is identified as a potential inhibitor of cell death in grape berries

Cell death (CD) in Vitis vinifera L grape berries, exemplified in Shiraz, occurs late in ripening influencing yield, berry and wine quality. Here we isolated and functionally characterised a BON1-associated gene, VvBAP1 from Shiraz berries, encoding a small protein with a C2 domain. VvBAP1 transcript increased during fruit development from veraison to harvest, and was significantly inhibited by drought stress 92 days after flowering when CD normally begins. This was correlated with high CD in Shiraz berries. The agrobacterium-mediated transient expression of VvBAP1 in tobacco leaves led to a decrease in electrolyte leakage and downregulated a marker gene (Hsr203J) for cell death. Expressing VvBAP1 in yeast (Saccharomyces cerevisiae) also alleviated cell death induced by hydrogen peroxide (H2O2). Overexpression of VvBAP1 in Arabidopsis increased resistance to H2O2 and reduced CD due to higher expression of genes involved in anti-oxidative responses. Arabidopsis overexpressing VvBAP1 displayed higher tolerance to drought accompanied by upregulation of antioxidant-related gene expression. VvBAP1 complemented an Arabidopsis bap1 knockout by abolishing its CD phenotypes. These results indicate that VvBAP1 may play a role in alleviating CD in grape berries and its downregulation under drought stress may be responsible for the generally observed increase in CD within the berry.

An H3K27me3 demethylase-HSFA2 regulatory loop orchestrates transgenerational thermomemory in Arabidopsis

Global warming has profound effects on plant growth and fitness. Plants have evolved sophisticated epigenetic machinery to respond quickly to heat, and exhibit transgenerational memory of the heat-induced release of post-transcriptional gene silencing (PTGS). However, how thermomemory is transmitted to progeny and the physiological relevance are elusive. Here we show that heat-induced HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2) directly activates the H3K27me3 demethylase RELATIVE OF EARLY FLOWERING 6 (REF6), which in turn derepresses HSFA2. REF6 and HSFA2 establish a heritable feedback loop, and activate an E3 ubiquitin ligase, SUPPRESSOR OF GENE SILENCING 3 (SGS3)-INTERACTING PROTEIN 1 (SGIP1). SGIP1-mediated SGS3 degradation leads to inhibited biosynthesis of trans-acting siRNA (tasiRNA). The REF6-HSFA2 loop and reduced tasiRNA converge to release HEAT-INDUCED TAS1 TARGET 5 (HTT5), which drives early flowering but attenuates immunity. Thus, heat induces transmitted phenotypes via a coordinated epigenetic network involving histone demethylases, transcription factors, and tasiRNAs, ensuring reproductive success and transgenerational stress adaptation.