Luciferase Complementation Assay for Protein-Protein Interactions in Plants

Loss of phytochromobilin synthase activity leads to larger seeds with higher protein content in soybean

Seed weight is an important agronomic trait that is related to seed size and determines yield in soybean (Glycine max). We previously identified a spontaneous soybean mutant with light green leaves called ygl2. Here, we cloned YGL2, which encodes a phytochromobilin (PΦB) synthase involved in synthesizing the chromophore of the photoreceptor phytochrome. The lesion in ygl2 is a 10-bp deletion, causing a frameshift mutation and a premature stop codon that truncates the encoded protein. In contrast to the wild type, ygl2 lacks PΦB synthase activity and function. This appears to promote cell expansion, thus increasing seed weight. Surprisingly, the ygl2 mutant also exhibits excellent traits including early maturity and high protein content. Moreover, under the condition of dense planting (3 cm), the yield of YGL2 mutant was significantly increased. Mutants harboring ygl2 mutations that we generated via gene editing had enlarged seeds with high protein content. Moreover, the expression levels of the photoperiod sensitive genes (E1, FT2a, FT5a) were lower in the ygl2 mutant than in the wild type. Mutating the YGL2 gene resulted in increased biliverdin content and decreased heme content. We determined that Lhcb4, a chlorophyll a/b binding protein in photosystem II, interacts with YGL2 but not with the mutant version of the protein. We thus identified a mutation in a PΦB synthase gene that enhances seed weight in soybean, providing a promising breeding target for this important crop.

Structural insight into PIF6-mediated red light signal transduction of plant phytochrome B

The red/far-red light receptor phytochrome B (phyB) plays essential roles in regulating various plant development processes. PhyB exists in two distinct photoreversible forms: the inactive Pr form and the active Pfr form. phyB-Pfr binds phytochrome-interacting factors (PIFs) to transduce red light signals. Here, we determined the cryo-electron microscopy (cryo-EM) structures of the photoactivated phyB-Pfr‒PIF6 complex, the constitutively active mutant phyBY276H‒PIF6 complex, and the truncated phyBNY276H‒PIF6 complex. In these structures, two parallel phyB-Pfr molecules interact with one PIF6 molecule. Red light-triggered rotation of the PΦB D-ring leads to the conversion of hairpin loops into α helices and the "head-to-head" reassembly of phyB-Pfr N-terminal photosensory modules. The interaction between phyB-Pfr and PIF6 influences the dimerization and transcriptional activation activity of PIF6, and PIF6 stabilizes the N-terminal extension of phyB-Pfr and increases the Pr→Pfr photoconversion efficiency of phyB. Our findings reveal the molecular mechanisms underlying Pr→Pfr photoconversion and PIF6-mediated red light signal transduction of phyB.

OsBIR3 maintains the homeostasis of OsBRI1, OsREM4.1, and Brd2 protein levels in brassinosteroid pathways in rice

Brassinosteroids (BRs) are a crucial class of plant hormones and regulate many important agronomic traits in crops. In Arabidopsis (Arabidopsis thaliana), BIR3 interacts with the BR receptor BRI1 and coreceptor BAK1 to negatively regulate BR signalling. In contrast, OsBIR3 interacts with OsBRI1 and OsBAK1 to positively regulate BR signalling in rice (Oryza sativa). However, our understanding of OsBIR3 remains incomplete. In this study, we isolated a reduced upper branch (rub1) mutant of rice, exhibiting a significant reduction in grain number. The causal gene for the mutant phenotype was LOC_Os04g41030 (OsBIR3). OsBIR3 interacts with both OsBRI1 and the remorin protein OsREM4.1, but interactions of the mutated Osbir3 with both OsBRI1 and OsREM4.1 were decreased. Furthermore, BL interferes with the interaction of OsBIR3 with OsBRI1, but promotes the interaction of OsBIR3 with OsREM4.1. Overexpression of OsREM4.1 and OsBRI1 individually in the rub1 mutant caused an exacerbation of the mutant phenotype. Additionally, OsBIR3 interacts with Brd2, involving BR biosynthesis in the early stage, and the interaction of the mutated brd2 with wild-type OsBIR3 was increased. Besides, BL promotes the interaction between OsBIR3 and Brd2. Collectively, the data indicate that OsBIR3 plays a key role in maintaining the homeostasis of OsBRI1, OsREM4.1, and Brd2 at their respective protein levels. This work provides insight into the roles of OsBIR3 in BR signalling and biosynthesis pathways of rice.

Transcription factor OsNAC29a confers drought tolerance through the ABA pathway in rice

The plant-specific NAC transcription factor family plays a crucial role in mediating responses to abiotic stress, but the functions of many NAC genes remain poorly characterized. The rice OsNAC29a gene is induced by PEG and abscisic acid (ABA). OsNAC29a exhibits transactivation activity and the region of 248-315 amino acids at its C-terminus is essential for its activation. Over-expression of OsNAC29a enhances drought resistance and ABA sensitivity in transgenic rice. OsNAC29a over-expression modulates physiological indicators related to stress resistance, while RNAi-mediated down-regulation of OsNAC29a results in opposite phenotypes and physiological changes. Under drought conditions, OsNAC29a over-expression significantly up-regulates stress-related genes such as OsP5CS1, OsSRO1c, OsPOD1, OsLEA3, and OsRab16C. Interestingly, OsPOD1 gene expression increases in OsNAC29a over-expression rice under both normal and drought stress conditions, leading to significantly enhanced peroxidase activity. Further research reveals that OsNAC29a binds to the OsPOD1 promoter to drive its expression. Additionally, OsSAPK2 which is a key component of the ABA-dependent drought-tolerance pathway interacts physically with OsNAC29a and enhances its transcriptional activation activity. Collectively, acting as a positive regulator of drought tolerance, OsNAC29a regulates drought resistance in rice by directly or indirectly modulating stress-responsive genes.

Late blight pathogen targets host Rab-G3 GTPases with an atypical GTPase-activating protein

Late blight pathogen Phytophthora infestans secretes numerous effectors to suppress plant immunity. However, little is known about their underlying biochemical mechanisms. Here we report that, in the host Nicotiana benthamiana, P. infestans core RXLR effector Pi17063 suppresses plant immunity by targeting the host plasma membrane and NbRab-G3 proteins, small GTPases of the Ras-related brain (Rab) family. Pi17063 functions as their specific GTPase-activating protein (GAP), driving them to the cytoplasm-localized guanosine diphosphate (GDP)-bound inactive state. Mutant analysis of the conserved Pi17063 arginine residues showed the essential role of its GAP activity for virulence contribution. All four NbRab-G3 subfamily members are positive immune regulators, and NbRab-G3c mutants lost the ability to switch between active and inactive states and showed compromised immune function. Consistent with this, both silencing and overexpression of an endogenous GAP, NbGYP, inhibited NbRab-G3c-mediated plant immunity. Our results revealed positive immune roles of host NbRab-G3 GTPases, the importance of their state balance, and the biochemical mechanism by which their functions are suppressed by a P. infestans effector, providing insights into understanding eukaryotic effector-mediated plant susceptibility.

γ-Aminobutyric acid modulates terpene biosynthesis through the ATG8a-mediated pathway

Terpenes play crucial roles in plant growth, development, and stress responses. The biosynthesis of terpenes is influenced by abiotic stress factors, such as drought, temperature, or light. However, the molecular network underlying how terpenes are regulated in response to environmental stimuli remains largely unknown. Here, we identified the autophagy protein SgATG8a as a key mediator of GABA-regulated terpene production and drought tolerance in Sindora glabra. SgATG8a, evolutionarily related to the animal GABA receptor-associated protein (GABARAP) subfamily, localizes in both the nucleus and cytoplasm. Exogenous GABA treatment not only increased the expression level of terpene synthase genes (SgTPSs) but also led to enhanced accumulation of six main terpene components in Sindora glabra. In addition, GABA alleviated the photosynthesis damage and enhanced leaf biomass under drought conditions. Consistently, overexpression of SgATG8a in Arabidopsis increased terpene synthase gene (SgTPS) expression, leading to the enhanced production of four major terpenes and improved the tolerance of transgenic plants to drought stress by regulating reactive oxygen species (ROS) scavenging systems. Moreover, the transcription factors SgWRKY13 and SgERF4 were identified as interacting partners of SgATG8a, activating SgTPS3 expression. Lectin receptor-like kinase (LecRK1) is involved in the GABA-mediated pathway by interacting with the SgWRKY13/SgERF4-SgATG8a proteins, and the LecRK1-SgWRKY13/SgERF4 phosphorylation module fine-tunes the transcription of the downstream SgTPS3 gene. Taken together, these findings reveal a novel role for GABA in regulating terpene biosynthesis and drought tolerance, providing insights into the molecular mechanism underlying GABA-mediated terpene production.

The IbDof2.1-IbABF2 module regulates abscisic acid responses and proline biosynthesis to enhance drought tolerance in sweetpotato

Drought is a major abiotic stress that impairs plant growth and development. Developing drought-tolerant crop varieties is an important goal of breeders. Transcription factors belonging to the DNA-binding with one zinc finger (Dof) family regulate plant stress responses and development. However, the roles and regulatory mechanisms of Dof2.1 members in plant stress tolerance are still unclear. Here, we cloned the IbDof2.1 gene from sweetpotato and found that its overexpression significantly enhanced drought tolerance of sweetpotato, whereas IbDof2.1-RNA interference (RNAi) plants displayed the opposite phenotype. The IbDof2.1-overexpression plants showed increased abscisic acid (ABA) and proline contents and stomatal sensitivity to ABA and decreased H2O2 accumulation. Furthermore, we found that IbDof2.1 interacted with ABA-binding factor 2 (IbABF2) and promoted the expression of the proline biosynthesis gene IbP5CS1 to increase proline content, further activating the reactive oxygen species (ROS) scavenging system. These results suggest that the IbDof2.1-IbABF2 module induces stomatal closure and activates the ROS scavenging system by regulating ABA responses and proline biosynthesis to enhance drought tolerance in sweetpotato. Our findings provide novel insights into the roles and regulatory mechanisms of Dof2.1 in plants.

Precise genome editing of Dense and Erect Panicle 1 promotes rice sheath blight resistance and yield production in japonica rice

The primary goals of crop breeding are to enhance yield and improve disease resistance. However, the "trade-off" mechanism, in which signalling pathways for resistance and yield are antagonistically regulated, poses challenges for achieving both simultaneously. Previously, we demonstrated that knock-out mutants of the Dense and Erect Panicle 1 (DEP1) gene can significantly enhance rice resistance to sheath blight (ShB), and we mapped DEP1's association with panicle length. In this study, we discovered that dep1 mutants significantly reduced rice yield. Nonetheless, truncated DEP1 was able to achieve both ShB resistance and yield increase in japonica rice. To further explore the function of truncated DEP1 in promoting yield and ShB resistance, we generated CRISPR/Cas9-mediated genome editing mutants, including a full-length deletion mutant of DEP1, named dep1, and a truncated version, dep1-cys. Upon inoculation with Rhizoctonia solani, the dep1-cys mutant demonstrated stronger ShB resistance than the dep1 mutant. Additionally, dep1-cys increased yield per plant, whereas dep1 reduced it. Compared to the full DEP1 protein, the truncated DEP1 (dep1-cys) demonstrated a decreased interaction affinity with IDD14 and increased affinity with IDD10, which are known to positively and negatively regulate ShB resistance through the activation of PIN1a and ETR2, respectively. The dep1-cys mutant exhibited higher PIN1a and lower ETR2 expression than wild-type plants, suggesting that dep1-cys modulated IDD14 and IDD10 interactions to regulate PIN1a and ETR2, thereby enhancing ShB resistance. Overall, these data indicate that precise genome editing of DEP1 could simultaneously improve both ShB resistance and yield, effectively mitigating trade-off regulation in rice.

Glutamate dehydrogenase MoGDH2 modulates the environmental and host pH to enhance adaptation and virulence of the rice blast fungus Pyricularia oryzae

pH adaptation and modulation are essential for the survival and infection of fungal pathogens. Pyricularia oryzae is a hemi-biotrophic fungal pathogen causes devastating blast disease on rice. How P. oryzae achieves host pH alkalization during the biotrophic-infection stage is unclear. Here, we characterized the NAD+-glutamate dehydrogenase encoding gene MoGDH2 in P. oryzae. The Δmogdh2 mutant failed to utilize glutamate to release NH3 and alkalize the environmental pH. MoGDH2 mediated pH homeostasis under acidic conditions but not alkaline environments. During glutamate utilization and fungal infection, MoGDH2 exhibited high expression levels, and modulated host pH at biotrophic stage. The apoplastic pH of host cells infected by wild-type strain P131 was sharply acidified at 24 h post inoculation (hpi), and the cytoplasmic pH gradually increased from 24 to 36 hpi. In comparison, the pH change patterns disappeared in cells infected by Δmogdh2. Furthermore, MoGDH2 is critical for reactive oxygen species tolerance and virulence, which is regulated via phosphorylation at the T47 site. Protein kinase MoDbf2 directly interacted with and phosphorylated MoGDH2. This study sheds new light on the function of MoGDH2 in pH modulation and infection.

Manipulation of the brown glume and internode 1 gene leads to alterations in the colouration of lignified tissues, lignin content and pathogen resistance in wheat

Lignin is a crucial component of the cell wall, providing mechanical support and protection against biotic and abiotic stresses. However, little is known about wheat lignin-related mutants and their roles in pathogen defence. Here, we identified an ethyl methanesulfonate (EMS)-derived Aegilops tauschii mutant named brown glume and internode 1 (bgi1), which exhibits reddish-brown pigmentation in various tissues, including internodes, spikes and glumes. Using map-based cloning and single nucleotide polymorphism (SNP) analysis, we identified AET6Gv20438400 (BGI1) as the leading candidate gene, encoding the TaCAD1 protein. The mutation occurred in the splice acceptor site of the first intron, resulting in a premature stop codon in BGI1. We validated the function of BGI1 using loss-of-function EMS and gene editing knockout mutants, both of which displayed reddish-brown pigmentation in lignified tissues. BGI1 knockout mutants exhibited reduced lignin content and shearing force relative to wild type, while BGI1 overexpression transgenic plants showed increased lignin content and enhanced disease resistance against common root rot and Fusarium crown rot. We confirmed that BGI1 exhibits CAD activity both in vitro and in vivo, playing an important role in lignin biosynthesis. BGI1 was highly expressed in the stem and spike, with its localisation observed in the cytoplasm. Transcriptome analysis revealed the regulatory networks associated with BGI1. Finally, we demonstrated that BGI1 interacts with TaPYL-1D, potentially involved in the abscisic acid signalling pathway. The identification and functional characterisation of BGI1 significantly advance our understanding of CAD proteins in lignin biosynthesis and plant defence against pathogen infection in wheat.

SLR1-LPA1 signal regulates sheath blight resistance and lamina joint angle in rice

Previous studies have suggested that Dense and Erect Panicle 1 (DEP1) interacts with Lose Plant Architecture 1 (LPA1) to regulate auxin transport by which DEP1-LPA1 modulates rice sheath blight (ShB) resistance. In this study, we identified that dep1 and lpa1 exhibited semi-dwarfism and dep1/lpa1 was shorter than the single mutant. LPA1 OX displayed higher height, whereas DEP1 OX exhibited similar height with wild-type. The gibberellic acid (GA)-dependent shoot growth was inhibited in dep1 and lpa1 while activated in LPA1 OX, suggesting that LPA1 may play a role in GA signaling transduction. Yeast two-hybrid screening revealed that slender rice 1 (SLR1), a GA signaling negative regulator, interacted with LPA1. Additionally, slr1 was less susceptible to ShB, whereas the GA signaling positive regulator DWARF1 mutant d1 was more susceptible to ShB. This suggested that GA signaling positively regulates rice resistance to ShB. Furthermore, slr1 was similar to LPA1 OX in terms of reduced lamina joint angle, whereas d1 did not show any difference. This implied that SLR1 may regulate LPA1 dependent signaling to control the lamina joint angle via a mechanism that was independent of GA signaling. Transcriptome data indicated that GA signaling and catabolic genes were regulated by LPA1. Transient and ChIP assays suggested that LPA1 bound to the promoter of gibberellin 2-beta-dioxygenase, a GA catabolic gene, to activate its expression. These findings indicated that LPA1 modulated GA homeostasis and SLR1 interacted with and inhibited LPA1 to regulate ShB resistance and lamina joint angle in rice.

Two tandem R2R3 MYB transcription factor genes cooperatively regulate anthocyanin accumulation in potato tuber flesh

Anthocyanin biosynthesis and accumulation determines the colour of tuber flesh in potato (Solanum tuberosum) and influences nutritional quality. However, the regulatory mechanism behind anthocyanin biosynthesis in potato tuber flesh remains unclear. In this study, we identified the Pigmented tuber flesh (Pf) locus through a genome-wide association study using 135 diploid potato landraces. Genome editing of two tandem R2R3 MYB transcription factor genes, StMYB200 and StMYB210, within the Pf locus demonstrated that both genes are involved in anthocyanin biosynthesis in tuber flesh. Molecular and biochemical assays revealed that StMYB200 promotes StMYB210 transcription by directly binding to a 1.7-kb insertion present in the StMYB210 promoter, while StMYB210 also regulates its own expression. Furthermore, StMYB200 and StMYB210 both activated the expression of the basic helix-loop-helix transcription factor gene StbHLH1 and interacted with StbHLH1 to regulate anthocyanin biosynthesis. An analysis of the StMYB210 promoter in different diploid potato accessions showed that the 1.7-kb insertion is associated with flesh colour in potato. These findings reveal the genetic and molecular mechanism by which the Pf locus regulates anthocyanin accumulation in tuber flesh and provide an important reference for breeding new potato varieties with colourful flesh.

The Exserohilum turcicum effector EtEC81 reprograms alternative splicing in maize and activates immunity

Some pathogen-derived effectors reprogram mRNA splicing in host plants to regulate plant immune responses. Whether effectors from Exserohilum turcicum, which causes northern corn leaf blight (NLB), interfere with RNA splicing remains unknown. We identify that the secreted protein EtEC81 (Exserohilum turcicum effector 81) modulates the alternative splicing (AS) of maize (Zea mays) pre-mRNAs and negatively regulates the pathogenicity of E. turcicum. EtEC81 physically interacts with MAIZE EtEC81-INTERACTING PROTEIN 1 (ZmEIP1), which associates with maize spliceosome components, modulates AS in host cells, and positively regulates defense responses against E. turcicum. Transcriptome analysis identifies 119 common events with altered AS in maize plants transiently overexpressing ZmEIP1 or EtEC81, suggesting that these factors cause the misregulation of cellular activities and thus induce immune responses. Together, our results suggest that the EtEC81 effector targets ZmEIP1 to reprogram pre-mRNA splicing in maize. These findings provide a mechanistic basis and potential target gene for preventing NLB.

A plant viral effector subverts FER-RALF1 module-mediated intracellular immunity

The receptor-like kinase FERONIA (FER) is a prominent member of the Catharanthus roseus RLK1 (CrRLK1L) family, functioning as a modulator of immune receptor kinase complex formation in response to rapid alkalinization factors (RALFs). Typically, FER recognizes mature extracellular RALFs to combat bacterial and fungal infections. However, any role of the FER-RALF signalling cascade in plant viral infections remains unexplored. Here, we used turnip mosaic virus (TuMV), an important member of the genus Potyvirus, and the host Nicotiana benthamiana as a model system to explore the role of the FER-RALF cascade in plant-virus interactions. RALF1 from N. benthamiana (NbRALF1) positively regulated host resistance to inhibit TuMV infection. Co-expression studies showed that this process does not involve the conserved RRXL and YISY motifs typically associated with RALF function. Instead, NbRALF1 induced cell death and significantly inhibited TuMV infection in a manner that depends on the entire RALF1 sequence and also NbFER. These results suggest a novel mechanism where NbRALF1 may inhibit viral infection through intracellular interactions with NbFER, differing from the previously reported extracellular FER-RALF interactions that induce resistance to fungi and bacteria. Furthermore, we discovered that TuMV 6K2 interacts with NbRALF1 and promotes its degradation through the 26S proteasome pathway, thereby counteracting the host resistance induced by the NbFER-NbRALF1 cascade. Our findings imply the existence of an uncharacterized intracellular immunity signalling pathway mediated by the NbFER-NbRALF1 cascade and reveal a mechanism by which plant viruses counteract RALF1-FER module-mediated immunity.

The G-protein β subunit SlGB1 regulates tyramine-derived phenolamide metabolism for shoot apex growth and development in tomato

The shoot apex is a critical determinant of plant growth, development, morphology, and yield. The G-protein β subunit (Gβ) is an essential regulator of apical meristem dynamics, yet its precise mechanism of action remains unclear, with notable interspecific variation. This study reveals that in the dicot tomato (Solanum lycopersicum), Gβ subunit mutants (Slgb1) display abnormal shoot morphogenesis and, in severe cases, shoot apex death. Such a phenotype has also been observed in monocot species, like maize (Zea mays) and rice (Oryza sativa), but not in the model dicot Arabidopsis (Arabidopsis thaliana). Using integrated multiomics and liquid chromatography-mass spectrometry, we identified a significant upregulation in tyramine-derived phenolamides in Slgb1 mutants, particularly N-p-trans-coumaroyltyramine (N-P-CT) and N-trans-feruloyltyramine (N-FT). Biochemical and genetic assays pinpointed tyramine hydroxycinnamoyl transferases (THTs) as the enzymes catalyzing N-P-CT and N-FT biosynthesis, with THT8 overexpression inducing shoot apex death. Comparative genomic analysis revealed the presence of a THT-mediated tyramine-derived phenolamide metabolic pathway in species exhibiting gb1 mutant-associated apex death, which is notably absent in Arabidopsis. Protein interaction assays showed that SlGB1 interacts with bHLH79 at the cell membrane and cytoplasm, thereby attenuating the bHLH79-MYB10 interaction within the nucleus, leading to altered THT expression and phenolamide biosynthesis. This study unravels the molecular mechanisms by which SlGB1 governs tomato shoot apex growth and development, highlighting interspecific differences critical for developing breeding strategies aimed at optimizing shoot apex architecture.

The cysteine protease RD19C suppresses plant immunity to Phytophthora by modulating copper chaperone ATX1 stability

Papain-like cysteine proteases (PLCPs) are pivotal in plant development and immunity, though their specific regulatory mechanisms in immune responses remain largely unexplored. In this study, we identify AtRD19C, a vacuole-localized PLCP, and demonstrate its role in negatively regulating plant immunity to Phytophthora parasitica. We show that AtRD19C suppresses the ethylene (ET) signaling pathway by destabilizing the copper chaperone AtATX1, which is essential for activating ET signaling through the ethylene receptor ETR1. Genetic and biochemical analyses reveal that AtATX1 and the ET signaling pathway positively regulate immunity against Phytophthora. Given the conserved roles of RD19C and ATX1 in Solanum tuberosum, our findings suggest a conserved mechanism by which RD19C and ATX1 regulate resistance to Phytophthora across plant species.

GLKs directly regulate carotenoid biosynthesis via interacting with GBFs in plants

Carotenoids are vital photosynthetic pigments for plants. Golden2-like transcription factors (GLKs) are widely recognized as major regulators of Chl biosynthesis and chloroplast development. However, despite GLKs being subjected to intensive investigations, whether GLKs directly regulate carotenoid biosynthesis and the molecular mechanisms by which GLKs transcriptionally activate their target genes remain unclear. Here, we report that GLKs directly regulate carotenoid biosynthesis and activate their target genes in a G-box binding factor (GBF)-dependent manner in Arabidopsis. Both in vitro and in vivo studies reveal that GLKs physically interact with GBFs to activate transcription of phytoene synthase (PSY), the gene encoding a rate-limiting enzyme for carotenoid biosynthesis. While GLKs possess transactivation activity, they depend on GBFs to directly bind to the G-box motif to modulate PSY expression. Loss of GBFs impairs GLK function in regulating carotenoid and Chl biosynthesis. Since the G-box motif is an enriched motif in the promoters of GLK-regulated genes, the GLK-GBF regulatory module likely serves as a common mechanism underlying GLK-regulated photosynthetic pigment biosynthesis and chloroplast development. Our findings uncover a novel regulatory machinery of carotenoid biosynthesis, discover a molecular mechanism of transcriptional regulation by GLKs, and divulge GLKs as important regulators to coordinate photosynthetic pigment synthesis in plants.

A wheat tandem kinase activates an NLR to trigger immunity

The role of nucleotide-binding leucine-rich repeat (NLR) receptors in plant immunity is well studied, but the function of a class of tandem kinases (TKs) that confer disease resistance in wheat and barley remains unclear. In this study, we show that the SR62 locus is a digenic module encoding the Sr62TK TK and an NLR (Sr62NLR), and we identify the corresponding AvrSr62 effector. AvrSr62 binds to the N-terminal kinase 1 of Sr62TK, triggering displacement of kinase 2, which activates Sr62NLR. Modeling and mutation analysis indicated that this is mediated by overlapping binding sites (i) on kinase 1 for binding AvrSr62 and kinase 2 and (ii) on kinase 2 for binding kinase 1 and Sr62NLR. Understanding this two-component resistance complex may help engineering and breeding plants for durable resistance.

An LRR-RLK protein modulates drought- and salt-stress responses in maize

Maize (Zea mays), which is a vital source of food, feed, and energy feedstock globally, has significant potential for higher yields. However, environmental stress conditions, including drought and salt stress, severely restrict maize plant growth and development, leading to great yield losses. Leucine-rich repeat receptor-like kinases (LRR-RLKs) function in biotic and abiotic stress responses in the model plant Arabidopsis (Arabidopsis thaliana), but their roles in abiotic stress responses in maize are not entirely understood. In this study, we determine that the LRR-RLK ZmMIK2, a homolog of the Arabidopsis LRR-RK MALE DISCOVERER 1 (MDIS1)-INTERACTING RECEPTOR LIKE KINASE 2 (MIK2), functions in resistance to both drought and salt stress in maize. Zmmik2 plants exhibit enhanced resistance to both stresses, whereas overexpressing ZmMIK2 confers the opposite phenotypes. Furthermore, we identify C2-DOMAIN-CONTAINING PROTEIN 1 (ZmC2DP1), which interacts with the intracellular region of ZmMIK2. Notably, that region of ZmMIK2 mediates the phosphorylation of ZmC2DP1, likely by increasing its stability. Both ZmMIK2 and ZmC2DP1 are mainly expressed in roots. As with ZmMIK2, knockout of ZmC2DP1 enhances resistance to both drought and salt stress. We conclude that ZmMIK2-ZmC2DP1 acts as a negative regulatory module in maize drought- and salt-stress responses.

The CsTM alters multicellular trichome morphology and enhances resistance against aphid by interacting with CsTIP1;1 in cucumber

The multicellular trichomes of cucumber (Cucumis sativus L.) serve as the primary defense barrier against external factors, whose impact extends beyond plant growth and development to include commercial characteristics of fruits. The aphid (Aphis gossypii Glover) is one of prominent pests in cucumber cultivation. However, the relationship between physical properties of trichomes and the aphid resistance at molecular level remains largely unexplored. Here, a spontaneous mutant trichome morphology (tm) was characterized by increased susceptibility towards aphid. Further observations showed the tm exhibited a higher and narrower trichome base, which was significantly distinguishable from that in wild-type (WT). We conducted map-based cloning and identified the candidate, CsTM, encoding a C-lectin receptor-like kinase. The knockout mutant demonstrated the role of CsTM in trichome morphogenesis. The presence of SNP does not regulate the relative expression of CsTM, but diminishes the CsTM abundance of membrane proteins in tm. Interestingly, CsTM was found to interact with CsTIP1;1, which encodes an aquaporin with extensive reports in plant resistance and growth development. The subsequent aphid resistance experiments revealed that both CsTM and CsTIP1;1 regulated the development of trichomes and conferred resistance against aphid by affecting cytoplasmic H2O2 contents. Transcriptome analysis revealed a significant enrichment of genes associated with pathogenesis, calcium binding and cellulose synthase. Overall, our study elucidates an unidentified mechanism that CsTM-CsTIP1;1 alters multicellular trichome morphology and enhances resistance against aphid, thus providing a wholly new perspective for trichome morphogenesis in cucumber.

A Ralstonia solanacearum Effector Targets Splicing Factor SR34a to Reprogram Alternative Splicing and Regulate Plant Immunity

Alternative splicing is a critical post-transcriptional regulatory mechanism in eukaryotes. While infection with Ralstonia solanacearum GMI1000 significantly alters plant alternative splicing patterns, the underlying molecular mechanisms remain unclear. Herein, the effect of the GMI1000 Type III secretion system effectors on alternative splicing in the tomato cultivar Heinz 1706 was investigated. The RNA-seq analysis confirmed genome-wide alternative splicing changes induced by the Type III secretion system in tomato, including 1386 differential alternatively spliced events across 1023 genes, many of which are associated with plant defense. Seven nucleus-localized Type III effectors were transiently expressed in an RLPK splicing reporter system transgenic tobacco, identifying RipP2 as an effector that modulates alternative splicing levels. Sequence analysis, protein-protein interaction assays, and AlphaFold2 structural predictions revealed that RipP2 interacted with the tomato splicing factor SR34a. Furthermore, RipP2 acetylated a conserved lysine at position 132 within the SWQDLKD motif of SR34a, regulating its splicing pattern in defense-related genes and modulating plant immunity. This study elucidates how the "RipP2-SR34a module" influences plant immune responses by regulating the alternative splicing of immune-related genes, providing new insights into pathogen-plant interactions and splicing regulation.

The calcium-dependent protein kinase CmaCPK4 regulates sex determination in pumpkin (Cucurbita maxima D.)

Pumpkin (Cucurbita maxima D.) is typically monoecious with individual male and female flowers, and its yield is associated with the degree of femaleness, i.e. the ratio of female to male flowers produced by the plant. Subgynoecy represents a sex form with a high degree of femaleness, but the regulatory mechanisms in pumpkin remain poorly understood. In this study, using the F2 population crossed from the subgynoecious line 2013-12 and the monoecious line 9-6, we initially identified a recessive locus to control the subgynoecious trait and named it sg1. After bulked segregant analysis with whole-genome resequencing and molecular marker linkage analysis, the sg1 locus was mapped to pumpkin Chromosome 2. Genetic sequence analysis found a pumpkin calcium-dependent protein kinase (CPK) gene, CmaCPK4, in the mapping interval as the candidate gene. A retrotransposon insertion identified within the promoter elevated CmaCPK4 expression in 2013-12. Morphological characterization of near-isogenic lines containing the sg1 allele showed increases in the ratio of female flowers and high ethylene contents in terminal buds compared with the receptor parent. Heterologous overexpression of CmaCPK4 significantly increased the ratio of female flowers in cucumber (Cucumis sativus). Furthermore, CmaCPK4 directly interacts with and phosphorylates 1-aminocyclopropane-1-carboxylate synthase 5 (CmaACS5) and 1-aminocyclopropane-1-carboxylate synthase 7 (CmaACS7), resulting in increased ethylene content in 2013-12, which affected pumpkin sex determination. These findings provide insights into the role of the CmaCPK4-CmaACS5/CmaACS7 module in ethylene-induced sex determination in pumpkin.

Control of H2S synthesis by the monomer-oligomer transition of OsCBSX3 for modulating rice growth-immunity balance

Hydrogen sulfide (H2S) is recognized as an important gaseous signaling molecule, similar to nitric oxide and carbon monoxide. However, less is known about the biosynthetic mechanism of H2S in plants and its role in plant-pathogen interactions. Here, we show that H2S induces the bursts of reactive oxygen species and upregulates the expression of defense-related genes in rice. However, excessive H2S concentrations inhibit rice growth. We found that the cystathionine β-synthase OsCBSX3 regulates rice growth and resistance to bacteria pathogens, Xanthomonas oryzae pv. oryzicola (Xoc) and X. oryzae pv. oryzae (Xoo), by modulating H2S biosynthesis. OsCBSX3 exists in both oligomeric and monomeric forms in rice. Compared with wild-type OsCBSX3, an oligomerization-disrupted mutant exhibits the reduced capacity for H2S synthesis, diminished resistance to X. oryzae, and inability to localize to the chloroplast. Upon pathogen infection, rice triggers PsbO-dependent oligomerization of OsCBSX3, leading to increased H2S production and enhanced defense responses. However, excessive concentrations of H2S reduce the oligomerized form of OsCBSX3, facilitating its dissociation from PsbO, an important subunit of photosystem II, and its binding to OsTrxZ, a member of the thioredoxin family. We further demonstrated that OsTrxZ can directly convert OsCBSX3 into monomers, thereby mitigating the excessive H2S synthesis and its negative effects on rice growth and development. Overexpression of PsbO enhances rice resistance to both Xoc and Xoo, whereas overexpression of OsTrxZ exerts the opposite effect. Taken together, these findings suggest that PsbO and OsTrxZ antagonistically modulate the interconversion between oligomeric and monomeric forms of OsCBSX3, thereby balancing rice resistance and developmental processes.

Phosphorylation-dependent activation of the bHLH transcription factor ICE1/SCRM promotes polarization of the Arabidopsis zygote

In Arabidopsis thaliana, the asymmetric cell division (ACD) of the zygote gives rise to the embryo proper and an extraembryonic suspensor, respectively. This process is controlled by the ERECTA-YODA-MPK3/6 receptor kinase-MAP kinase-signaling pathway, which also orchestrates ACDs in the epidermis. In this context, the bHLH transcription factor ICE1/SCRM is negatively controlled by MPK3/6-directed phosphorylation. However, it is unknown whether this regulatory module is similarly involved in the zygotic ACD. We investigated the function of SCRM in zygote polarization by analyzing the effect of loss-of-function alleles and variants that cannot be phosphorylated by MPK3/6, protein accumulation, and target gene expression. Our results show that SCRM has a critical function in zygote polarization and acts in parallel with the known MPK3/6 target WRKY2 in activating WOX8. Our work further demonstrates that SCRM activity in the early embryo is positively controlled by MPK3/6-mediated phosphorylation. Therefore, the effect of MAP kinase-directed phosphorylation of the same target protein fundamentally differs between the embryo and the epidermis, shedding light on cell type-specific, differential gene regulation by common signaling pathways.

Transcriptome analysis of tree peony under high temperature treatment and functional verification of PsDREB2A gene

Paeonia suffruticosa is a plant of Paeonia in Paeoniaceae. It is an important woody ornamental flower in the world. High temperature in summer hinders the growth of tree peony and reduces its ornamental quality, which restricts the cultivation and application of tree peony in Jiangnan area of China. Paeonia suffruticosa 'Hu Hong' is a traditional Chinese tree peony variety with high ornamental value. It is an excellent parent material for cultivating heat-resistant peony. This paper selected the tree peony variety 'Hu Hong' as the material. The transcriptome data of Paeonia suffruticosa 'Hu Hong' at 0, 2, 6, 12 and 24 h after high temperature treatment were analyzed by RNA-Seq method. At each time point, a large number of significantly differentially expressed genes(DEGs) were screened between tree peony cultured at high temperature and room temperature. The analysis of the common DEGs in the four comparison groups showed that the differential genes were mainly enriched in the GO terms ' protein processing in endoplasmic reticulum', 'Pentose and glucuronate interconversions ', ' plant-pathogen interaction ', ' zeatin biosynthesis ', ' fatty acid elongation ', and ' plant hormone signal transduction ' pathways. Abscisic acid(ABA), ethylene(ET) and brassinosteroid(BR) signaling related genes were significantly up-regulated in 'Hu Hong' to resist high temperature treatment. In the auxin(IAA), cytokinin(CTK), gibberellin(GA), salicylic acid(SA) pathways, compared with the control group, the down-regulated expression was involved in hormone signal transduction to respond to high temperature treatment. A total of 62 TFs from 28 different families were annotated, with the AP2/ERF family annotating the largest number. Among the TFs annotated to the AP2/ERF family, the highest expression gene PsDREB2A was found. Overexpression of PsDREB2A Arabidopsis plants improved heat tolerance under high temperature treatment. However, silencing PsDREB2A in tree peony resulted in a heat-intolerant phenotype. PsDREB2A can directly bind to the DRE-core motif in the PsHSFA3 promoter to initiate its expression. In addition, PsHSFA3-overexpressing plants showed higher heat resistance, while PsHSFA3-silenced plants showed lower heat resistance. This study provides a scientific basis for in-depth study of the molecular mechanism of high temperature treatment response in tree peony, improving the heat signal transduction regulation network of tree peony, and mining heat-resistant related genes.

Deciphering the core shunt mechanism in Arabidopsis cuticular wax biosynthesis and its role in plant environmental adaptation

Plant cuticular waxes serve as highly responsive adaptations to variable environments1-7. Aliphatic waxes consist of very-long-chain (VLC) compounds produced from 1-alcohol- or alkane-forming pathways5,8. The existing variation in 1-alcohols and alkanes across Arabidopsis accessions revealed that 1-alcohol amounts are negatively correlated with aridity factors, whereas alkanes display the opposite behaviour. How carbon resources are allocated between the 1-alcohol and alkane pathways responding to environmental stimuli is still largely unknown. Here, in Arabidopsis, we report a novel 1-alcohol biosynthesis pathway in which VLC acyl-CoAs are first reduced to aldehydes by CER3 and then converted into 1-alcohols via a newly identified putative aldehyde reductase SOH1. CER3, previously shown to interact with CER1 in alkane synthesis, is identified to interact with SOH1 as well, channelling wax precursors into either alcohol- or alkane-forming pathways, and the directional shunting of these precursors is tightly regulated by the SOH1-CER3-CER1 module in response to environmental conditions.

PpNAP4 and ethylene act in a regulatory loop to modulate peach fruit ripening and softening

Ripening significantly influences fruit quality and commercial value. Peaches (Prunus persica), a climacteric fruit, exhibit increased ethylene biosynthesis and decreased fruit firmness during ripening. NAC-like proteins activated by AP3/P1 (NAP) proteins are a subfamily of NAC transcription factors, and certain NAPs have been shown to intervene in fruit ripening. Here, we revealed that one NAP member PpNAP4, along with ethylene, positively regulated peach ripening and softening. Positive regulation of fruit ripening by PpNAP4 was demonstrated by overexpressing PpNAP4 in both peaches and tomatoes, resulting in enhanced fruit ripening through targeted modulation of specific ethylene biosynthesis and cell wall degradation-related genes. Further investigation revealed that PpNAP4 targets and upregulates key ethylene biosynthesis genes PpACS1, PpACO1 and PpEIN2, which is the core component of ethylene signaling. PpNAP4 positively modulates fruit softening by binding to and activating the promoters of cell wall degradation-related genes PpPL1 and PpPL15. Additionally, expression of PpPL1 and PpPL15 was directly affected by ethylene, with further investigation revealing that their promoters were clearly induced by ethylene. Our findings demonstrated a synergistic role played by the interaction between PpNAP4 and PpNAP6, enhancing the expression of PpACS1, PpACO1, PpPL1, PpPL15 and PpEIN2, thereby contributing to fruit ripening and softening. Overall, our study revealed the intricate mechanisms responsible for PpNAP4, PpNAP6, and ethylene roles during peach fruit ripening, highlighting a regulatory loop in which PpNAP4 and ethylene mutually enhance each other during the ripening process. These enhancements further contribute to peach fruit softening by upregulating specific cell wall degradation-related genes.

DREPP protein StPCaP1 facilitates the cell-to-cell movement of Potato virus Y and Potato virus S by inhibiting callose deposition at plasmodesmata

Plant viruses, constrained by their limited genomic coding capacity, rely significantly on host factors for successful infection. Disruption of these essential host factors can confer resistance to viruses, with such factors categorized as susceptibility genes or recessive resistance genes. Recent research has identified developmentally regulated plasma membrane polypeptide (DREPP) proteins as susceptibility factors integral to the cell-to-cell movement of potyviruses. In the present study, we demonstrated that the silencing of StPCaP1, a DREPP gene in potato, confers novel resistance to both Potato virus Y (PVY, Potyvirus) and Potato virus S (PVS, Carlavirus). Interaction and subcellular localization analyses revealed that the movement proteins (MPs) of PVY (P3NPIPO) and PVS (TGB1) interact with StPCaP1, recruiting it to plasmodesmata (PD). Furthermore, transcriptome analysis and experimental validation indicated that compared to wild-type (WT) controls, StPCaP1-silenced lines exhibit significantly increased glucose content and elevated expression levels of several UDP-glucosyltransferases (UGTs), which are potential components of the callose synthesis complex. These findings suggest that StPCaP1 participates in callose deposition, as evidenced by the increased callose deposition at PD and reduced PD permeability observed in StPCaP1-silenced lines. Additionally, we found that StPCaP1 expression in Nicotiana benthamiana led to reduced callose deposition at PD and promoted PVY-GFP cell-to-cell movement in NbPCaP1-silenced plants in a concentration-dependent manner, which suggests the changes in callose deposition at PD induced by StPCaP1 relates to viral cell-to-cell movement. This study provides a deeper understanding of DREPP-mediated viral movement and highlights potential targets for developing virus-resistant crops.

The HISTONE ACETYLTRANSFERASE 1 interacts with CONSTANS to promote flowering in Arabidopsis

Chromatin modifications, including histone acetylation, play essential roles in regulating flowering. The CBP/p300 family HISTONE ACETYLTRANSFERASE 1 (HAC1), which mediates histone acetylation, promotes the process of floral transition; however, the precise mechanism remains largely unclear. Specifically, how HAC1 is involved in the flowering regulatory network and which genes are the direct targets of HAC1 during flowering regulation are still unknown. In this study, we elucidated the critical function of HAC1 in promoting flowering via exerting active epigenetic markers at two key floral integrators, FT and SOC1, thereby regulating their expression to trigger the flowering process. We show that HAC1 physically interacts with CONSTANS (CO) in vivo and in vitro. Chromatin immunoprecipitation results indicate that HAC1 directly binds to the FT and SOC1 loci. Loss of HAC1 impairs CO-mediated transcriptional activation of FT and SOC1 in promoting flowering. Moreover, CO mutation leads to the decreased enrichment of HAC1 at FT and SOC1, indicating that CO recruits HAC1 to FT and SOC1. Finally, HAC1, as well as CO, is required for the elevated histone acetylation level at FT and SOC1. Taken together, our finding reveals that HAC1-mediated histone acetylation boots flowering via a CO-dependent activation of FT and SOC1.

Loss-of-function of SSIIa and SSIIIa confers high resistant starch content in rice endosperm

Rice (Oryza sativa L.) endosperm accumulates huge amounts of starch. Rice starch is highly digestible, potentially enhancing the occurrence of blood sugar- and intestine-related diseases such as type 2 diabetes. Resistant starch (RS) is hardly digestible in small intestine but can be converted into beneficial short-chain fatty acids in large intestine, potentially reducing the incidence of these diseases. However, it is still difficult to produce a high RS rice variety. Here, we report that simultaneous deficiency of soluble starch synthases IIa and IIIa confers high RS content in rice endosperm. The ssIIa ssIIIa exhibited higher RS content than did the ssIIIa ssIIIb, a mutant reported currently to have remarkably higher RS content than parental ssIIIa, under our experimental conditions. Loss-of-function of SSIIa and SSIIIa significantly elevated the activity of granule-bound starch synthase I and thus content of amylose. Furthermore, total lipid content increased in mutant seeds, implying that intermediate metabolites spilled out from starch biosynthesis into lipid biosynthesis. The increased amylose content and improved lipid synthesis coordinately contributed to high RS content in mutant seeds. These results further reveal the molecular mechanism of RS occurrence in rice endosperm and provide a critical genetic resource for breeding higher RS rice cultivars.

MdLRR-RLK1-MdATG3 module enhances the resistance of apples to abiotic stress via autophagy

Apple is an important economic species affected by abiotic stress, such as salt and drought. LRR-RLKs play a key role in plant responses to stress, although their physiological functions under abiotic stress are not yet fully understood. Autophagy is a highly conserved process in eukaryotes, which plays a vital role in drought and salt stress responses. In this study, overexpression of MdLRR-RLK1 in apple promoted plant growth and development and increased salt and drought stress tolerance. MdLRR-RLK1 interacts with MdATG3 in vivo and in vitro, and MdATG3 ubiquitinates and degrades MdLRR-RLK1. Intriguingly, MdLRR-RLK1 and MdATG3 enhance salt and drought tolerance through increasing autophagy. Moreover, MdATG3 interacts with MdATG8F and MdATG8I-like in apple. These findings reveal the interaction between MdLRR-RLK1 and MdATG3, suggesting mechanisms that regulate apple growth and resistance to abiotic stress.

Glycerophosphodiester phosphodiesterase 1 mediates G3P accumulation for Eureka lemon resistance to citrus yellow vein clearing virus

Glycerophosphodiester phosphodiesterase 1 (GDPD1) plays an important function in the abiotic stress responses and participates in the accumulation of sn-glycerol-3-phosphate (G3P) in plants, which is key to plant systemic acquired resistance (SAR). However, the role of GDPD1 in plant responses to biotic stress remains poorly understood. This study characterized the antivirus function of the GDPD1 gene (designated as ClGDPD1) from Eureka lemon. ClGDPD1 is located in the membrane and endoplasmic reticulum, where it interacts with the citrus yellow vein clearing virus (CYVCV) coat protein (CP). Compared to individually expressed ClGDPD1 or coexpressed ClGDPD1 + CP140-326, transiently coexpressed ClGDPD1 + CP or ClGDPD1 + CP1-139 significantly upregulated the key substance contents and genes expression involved in glycerophospholipid metabolism. Over-expression of ClGDPD1 significantly facilitated the accumulation of G3P, upregulated the expression of SAR-related genes, and increased the resistance of transgenic Eureka lemon to CYVCV infection. Furthermore, exogenous glycerol treatment and over-expression of ClGPDH increased the G3P content and reduced CYVCV titers in plants or hairy roots. These results indicated that the enhanced resistance of ClGDPD1 transgenic Eureka lemon to CYVCV may be due to facilitating G3P accumulation through the interaction of ClGDPD1 with CP. Our findings provide novel insights into the role of ClGDPD1 as an important regulatory center in mediating the citrus defense response to viral infections.

The BBX7/8-CCA1/LHY transcription factor cascade promotes shade avoidance by activating PIF4

Sun-loving plants undergo shade avoidance syndrome (SAS) to compete with their neighbors for sunlight in shade conditions. Phytochrome B (phyB) plays a dominant role in sensing the shading signals (low red to far-red ratios) and triggering SAS. Shade drives phyB conversion to inactive form, consequently leading to the accumulation of PHYTOCHROMEINTERACTING FACTOR 4 (PIF4) that promotes plant growth. Here, we show B-box PROTEIN 7 (BBX7)/BBX8 and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1)/LATE ELONGATED HYPOCOTYL (LHY) positively regulate the low R : FR-induced PIF4 expression and promote the low R : FR-triggered hypocotyl growth in Arabidopsis. Shade interferes the interactions of phyB with BBX7 or BBX8 and triggers the accumulation of BBX7 and BBX8 independent of phyB. BBX7 and BBX8 associate with CCA1 and LHY to activate their transcription, the gene produces of which subsequently upregulate the expression of PIF4 in shade. Genetically, BBX7 and BBX8 act upstream of CCA1, LHY, and PIF4 with respect to hypocotyl growth in shade conditions. Our study reveals the BBX7/8-CCA1/LHY transcription factor cascade upregulates PIF4 expression and increases its abundance to promote plant growth and development in response to shade.

Two NPC1 homologous proteins are involved in asexual reproduction, pathogenicity, and lipid trafficking in Phytophthora sojae

Niemann-Pick type C (NPC) disease is characterized by lysosomal lipid storage disorders and defects in lipid trafficking, primarily due to mutations in the NPC1 protein. Two NPC1 homologous proteins are present in the genome of Phytophthora sojae, named as PsNPC1-1 and PsNPC1-2. Both proteins exhibit high sequence identity, consistent conserved functional domains, similar gene expression patterns, and comparable subcellular localization. Deletion of a single PsNPC1 gene did not result in significant phenotypic changes. However, simultaneous deletion of both PsNPC1 genes led to reduced mycelial growth, decreased sporangial production, impaired pathogenicity, and an inability to release normal zoospores in P. sojae. Furthermore, dysfunction of PsNPC1s did not completely block the absorption and utilization of exogenous sterols by P. sojae. While lipidome analysis revealed that the relative contents of fatty acyls, sphingolipids and saccharolipids were significantly elevated in the double-gene deletion mutant, alongside obvious alterations in glycerophospholipid and glycerolipid metabolism. Additionally, we observed a significant down-regulation of PsCDP-AP protein along with its interactions with both PsNPC1s. Deletion of PsCDP-AP also impaired asexual reproduction and virulence of P. sojae. These findings demonstrate that both PsNPC1 proteins may collaborate with other key regulators to modulate asexual reproduction, pathogenicity and lipid trafficking in P. sojae.

The OXIDATIVE SIGNAL-INDUCIBLE1 kinase regulates plant immunity by linking microbial pattern-induced reactive oxygen species burst to MAP kinase activation

Plant cell surface-localized pattern recognition receptors (PRRs) recognize microbial patterns and activate pattern-triggered immunity (PTI). Typical PTI responses include reactive oxygen species (ROS) burst controlled by the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RbohD) and activation of the MAP kinase (MAPK) cascade composed of MAPKKK3/5-MKK4/5-MPK3/6. However, the mechanisms through which PRRs regulate and coordinate these immune responses are not fully understood. Here, we showed that Arabidopsis thaliana OXIDATIVE SIGNAL-INDUCIBLE1 (OXI1), a kinase known to be activated by ROS, is involved in the LYK5-CERK1 receptor complex, which recognizes fungal cell wall-derived chitin. The oxi1 mutant exhibits enhanced susceptibility to various pathogens and reduced chitin-induced MAPK activation and ROS burst. We showed that chitin induces the phosphorylation of OXI1 in an RbohD-dependent manner. H2O2 and chitin treatment causes the oxidation of OXI1 at Cys104 and Cys205, which is essential for the kinase activity of OXI1. These oxidation sites are required for chitin-induced MAPK activation and disease resistance. Activated OXI1 directly phosphorylates MAPKKK5 to regulate MAPK activation. Additionally, OXI1 phosphorylates RbohD, suggesting that it may activate RbohD to promote ROS burst to further enhance the long-term MAPK activation. Together, our findings reveal a pathway linking PRR-mediated ROS production to MAPK activation through OXI1.

Phosphorylation of the transcription factor OsNAC29 by OsMAPK3 activates diterpenoid genes to promote rice immunity

Well-conserved mitogen-activated protein kinase (MAPK) cascades are essential for orchestrating of a wide range of cellular processes in plants, including defense responses against pathogen attack. NAC transcription factors (TFs) play important roles in plant immunity, but their targets and how they are regulated remain largely unknown. Here, we identified the TF OsNAC29 as a key component of a MAPK signaling pathway involved in rice (Oryza sativa) disease resistance. OsNAC29 binds directly to CACGTG motifs in the promoters of OsTPS28 and OsCYP71Z2, which are crucial for the biosynthesis of the phytoalexin 5,10-diketo-casbene and consequently rice blast resistance. OsNAC29 positively regulates rice blast resistance by promoting the expression of of OsTPS28 and OsCYP71Z2, and the function of OsNAC29 is genetically dependent on OsCYP71Z2 and OsTPS28. Furthermore, OsNAC29 interacts with OsRACK1A and OsMAPK3/6 to form an immune complex; OsMAPK3 phosphorylates OsNAC29 at Thr304 to prevent its proteasome-mediated degradation and promote its function against rice blast fungus. Phosphorylation of OsNAC29 at Thr304 is induced upon Magnaporthe oryzae infection and chitin treatment. Our data demonstrate the positive role of the OsMAPK3-OsNAC29-OsTPS28/OsCYP71Z2 module in rice blast resistance, providing insights into the molecular regulatory network and fine-tuning of NAC TFs in rice immunity.

Interaction of PASTICCINO2 with Golgi anti-apoptotic proteins confers resistance to endoplasmic reticulum stress and is dependent on very-long-chain fatty acids

The endoplasmic reticulum (ER) is crucial for maintaining cell homeostasis because it is the primary site for synthesizing secreted and transmembrane proteins and lipids. The unfolded protein response (UPR) is activated to restore the homeostasis of the ER when it is under stress; however, the relationship between lipids and the ER stress response in plants is not well understood. Arabidopsis GOLGI ANTI-APOPTOTIC PROTEINS (GAAPs) are involved in resisting ER stress, and in this study, we found that PASTICCINO2 (PAS2), which is involved in very-long-chain fatty acid (VLCFA) synthesis, interacts with GAAPs and INOSITOL REQUIRING ENZYME 1. The pas2 single-mutant and the gaap1 pas2 and gaap2 pas2 double-mutants exhibited increased seedling damage and an impaired UPR response under chronic ER stress. Site mutation combined with genetic analysis revealed that the role of PAS2 in resisting ER stress depended on its VLCFA synthesis domain. VLCFA contents were increased under ER stress, and this required GAAPs. Exogenous VLCFAs partially restored the defect in the activation of the UPR caused by mutation of PAS2 or GAAP under chronic ER stress. Our findings demonstrate that the association of PAS2 with GAAPs confers plant resistance to ER stress by regulating VLCFA synthesis and the UPR. This provides a basis for further studies on the connection between lipids and cell-fate decisions under stress.

Lemon zinc finger protein ClSUP induces accumulation of reactive oxygen species and inhibits citrus yellow vein-clearing virus infection via interactions with ClDOF3.4

Citrus yellow vein-clearing virus (Potexvirus citriflavivenae; CYVCV) is an increasing threat to citrus cultivation. Notably, the role of zinc finger proteins (ZFPs) in mediating viral resistance in citrus plants is unclear. In this study, we demonstrated that ZFPs ClSUP and ClDOF3.4 enhanced citrus defense responses against CYVCV in Eureka lemon (Citrus limon 'Eureka'). ClSUP interacted with the coat protein (CP) of CYVCV to reduce CP accumulation and inhibited its silencing suppressor function. Overexpression of CISUP triggered reactive oxygen species (ROS) and salicylic acid (SA) pathways, and enhanced resistance to CYVCV infection. In contrast, ClSUP silencing resulted in increased CP accumulation and down-regulated ROS and SA-related genes. ClDOF3.4 interacted with ClSUP to facilitate its interactions with CP. Furthermore, ClDOF3.4 synergistically regulated the accumulation of ROS and SA with ClSUP and accelerated down-regulation of CP accumulation. Transgenic plants co-expressing ClSUP and ClDOF3.4 significantly decreased the CYVCV. These findings provide a new reference for understanding the interaction mechanism between the host and CYVCV.

Tomato NADPH oxidase SlWfi1 interacts with the effector protein RipBJ of Ralstonia solanacearum to mediate host defence

Reactive oxygen species (ROS) play a crucial role in regulating numerous functions in organisms. Among the key regulators of ROS production are NADPH oxidases, primarily referred to as respiratory burst oxidase homologues (RBOHs). However, our understanding of whether and how pathogens directly target RBOHs has been limited. In this study, we revealed that the effector protein RipBJ, originating from the phytopathogenic bacterium Ralstonia solanacearum, was present in low- to medium-virulence strains but absent in high-virulence strains. Functional genetic assays demonstrated that the expression of ripBJ led to a reduction in bacterial infection. In the plant, RipBJ expression triggered plant cell death and the accumulation of H2O2, while also enhancing host defence against R. solanacearum by modulating multiple defence signalling pathways. Through protein interaction and functional studies, we demonstrated that RipBJ was associated with the plant's plasma membrane and interacted with the tomato RBOH known as SlWfi1, which contributed positively to RipBJ's effects on plants. Importantly, SlWfi1 expression was induced during the early stages following R. solanacearum infection and played a key role in defence against this bacterium. This research uncovers the plant RBOH as an interacting target of a pathogen's effector, providing valuable insights into the mechanisms of plant defence.

Dual roles of AtNBR1 in regulating selective autophagy via liquid-liquid phase separation and recognition of non-ubiquitinated substrates in Arabidopsis

Selective macroautophagy/autophagy in metazoans involves the conserved receptors NBR1 and SQSTM1/p62. Both autophagy receptors manage ubiquitinated cargo recognition, while SQSTM1 has an additional, distinct role of facilitating liquid-liquid phase separation (LLPS) during autophagy. Given that plants lack SQSTM1, it is postulated that plant NBR1 may combine activities of both metazoan NBR1 and SQSTM1. However, the precise mechanism by which plant NBR1 recognizes non-ubiquitinated substrates and its ability to undergo LLPS during selective autophagy remain elusive. Here, we implicate both the ZZ-type zinc finger motif and the four-tryptophan domain of Arabidopsis NBR1 (AtNBR1) in the recognition of non-ubiquitinated cargo proteins. Additionally, we reveal that AtNBR1 indeed undergoes LLPS prior to ATG8-mediated autophagosome formation, crucial for heat stress resistance in Arabidopsis. Our findings unveil the dual roles of AtNBR1 in both cargo recognition and LLPS during plant autophagy and advance our understanding of NBR1-mediated autophagy in plants compared to metazoans.Abbreviations: ATG8: autophagy 8; Co-IP: co-immunoprecipitation; EXO70E2: exocyst subunit EXO70 family protein E2; FRAP: fluorescence recovery after photobleaching; FW domain: four-tryptophan domain; GFP: green fluorescent protein; HS: heat stress; LLPS: liquid-liquid phase separation; LIR: LC3-interacting region; NBR1: next to BRCA1 gene 1; PAS: phagophore assembly site; PB1 domain: Phox and Bem1 domain; RFP: red fluorescent protein; ROF1: rotamase FKBP 1; SARs: selective autophagy receptors; UBA domain: ubiquitin-associated domain; Y2H: yeast two-hybrid; ZZ domain: ZZ-type zinc finger motif domain.

COLD6-OSM1 module senses chilling for cold tolerance via 2',3'-cAMP signaling in rice

While it is known that temperature sensors trigger calcium (Ca2+) signaling to confer cold tolerance in cells, less is known about sensors that couple with other secondary messengers. Here, we identify a cold sensor complex of CHILLING-TOLERANCE DIVERGENCE 6 (COLD6) and osmotin-like 1 (OSM1), which triggers 2',3'-cyclic adenosine monophosphate (2',3'-cAMP) production to enhance cold tolerance in rice. COLD6, which is encoded by a major quantitative trait locus (QTL) gene, interacts with the rice G protein α subunit (RGA1) at the plasma membrane under normal conditions. Upon exposure to chilling, cold-induced OSM1 binds to COLD6, kicking out RGA1 from interaction. This triggers an elevation of 2',3'-cAMP levels for enhancing chilling tolerance. Genetic data show that COLD6 negatively regulates cold tolerance and functionally depends on OSM1 in chilling stress. COLD6 alleles were selected during rice domestication. Knockout and natural variation of COLD6 in hybrid rice enhanced chilling tolerance, hinting design potential for breeding. This highlighted a module triggering 2',3'-cAMP to improve chilling tolerance in crops.

A cytoplasmic osmosensing mechanism mediated by molecular crowding-sensitive DCP5

Plants are frequently challenged by osmotic stresses. How plant cells sense environmental osmolarity changes is not fully understood. We report that Arabidopsis Decapping 5 (DCP5) functions as a multifunctional cytoplasmic osmosensor that senses and responds to extracellular hyperosmolarity. DCP5 harbors a plant-specific intramolecular crowding sensor (ICS) that undergoes conformational change and drives phase separation in response to osmotically intensified molecular crowding. Upon hyperosmolarity exposure, DCP5 rapidly and reversibly assembles to DCP5-enriched osmotic stress granules (DOSGs), which sequestrate plenty of mRNA and regulatory proteins, and thus adaptively reprograms both the translatome and transcriptome to facilitate plant osmotic stress adaptation. Our findings uncover a cytoplasmic osmosensing mechanism mediated by DCP5 with plant-specific molecular crowding sensitivity and suggest a stress sensory function for hyperosmotically induced stress granules.

Comprehensive genomic analysis of CiPawPYL-PP2C-SnRK family genes in pecan (Carya illinoinensis) and functional characterization of CiPawSnRK2.1 under salt stress responses

Abscisic acid (ABA) is a pivotal regulator of plant growth, development, and responses to environmental stresses. The ABA signaling pathway involves three key components: ABA receptors known as PYLs, PP2Cs, and SnRK2s, which are conserved across higher plants. This study comprehensively investigated the PYL-PP2C-SnRK gene family in pecan, identifying 14 PYL genes, 97 PP2C genes, and 44 SnRK genes, which were categorized into subgroups through phylogenetic and sequence structure analysis. Whole-genome duplication (WGD) and dispersed duplication (DSD) were identified as major drivers of family expansion, and purifying selection was the primary evolutionary force. Tissue-specific expression analysis suggested diverse functions in different pecan tissues. qRT-PCR validation confirmed the involvement of CiPawPYLs, CiPawPP2CAs, and CiPawSnRK2s in salt stress response. Subcellular localization analysis revealed CiPawPP2C1 in the nucleus and CiPawPYL1 and CiPawSnRK2.1 in both the nucleus and the plasma membrane. In addition, VIGS indicated that CiPawSnRK2.1-silenced pecan seedling leaves display significantly reduced salt tolerance. Y2H and LCI assays verified that CiPawPP2C3 can interact with CiPawPYL5, CiPawPYL8, and CiPawSnRK2.1. This study characterizes the role of CiPawSnRK2.1 in salt stress and lays the groundwork for exploring the CiPawPYL-PP2C-SnRK module, highlighting the need to investigate the roles of other components in the pecan ABA signaling pathway.

Eggplant NAC domain transcription factor SmNST1 as an activator promotes secondary cell wall thickening

NAC-domain transcription factors (TFs) are plant-specific transcriptional regulators playing crucial roles in plant secondary cell wall (SCW) biosynthesis. SCW is important for plant growth and development, maintaining plant morphology, providing rigid support, ensuring material transportation and participating in plant stress responses as a protective barrier. However, the molecular mechanisms underlying SCW in eggplant have not been thoroughly explored. In this study, the NAC domain TFs SmNST1 and SmNST2 were cloned from the eggplant line 'Sanyue qie'. SmNST1 and SmNST2 expression levels were the highest in the roots and stems. Subcellular localization analysis showed that they were localized in the cell membrane and nucleus. Their overexpression in transgenic tobacco showed that SmNST1 promotes SCW thickening. The expression of a set of SCW biosynthetic genes for cellulose, xylan and lignin, which regulate SCW formation, was increased in transgenic tobacco. Bimolecular fluorescence and luciferase complementation assays showed that SmNST1 interacted with SmNST2 in vivo. Yeast one-hybrid, electrophoretic mobility shift assay (EMSA) and Dual-luciferase reporter assays showed that SmMYB26 directly bound to the SmNST1 promoter and acted as an activator. SmNST1 and SmNST2 interact with the SmMYB108 promoter and repress SmMYB108 expression. Altogether, we showed that SmNST1 positively regulates SCW formation, improving our understanding of SCW biosynthesis transcriptional regulation.

Wild rice GL12 synergistically improves grain length and salt tolerance in cultivated rice

The abounding variations in wild rice provided potential reservoirs of beneficial genes for rice breeding. Maintaining stable and high yields under environmental stresses is a long-standing goal of rice breeding but is challenging due to internal trade-off mechanisms. Here, we report wild rice GL12W improves grain length and salt tolerance in both indica and japonica genetic backgrounds. GL12W alters cell length by regulating grain size related genes including GS2, and positively regulates the salt tolerance related genes, such as NAC5, NCED3, under salt stresses. We find that a G/T variation in GL12 promoter determined its binding to coactivator GIF1 and transcription factor WRKY53. GIF1 promotes GL12W expression in young panicle and WRKY53 represses GL12W expression under salt stresses. The G/T variation also contributes to the divergence of indica and japonica subspecies. Our results provide useful resources for modern rice breeding and shed insights for understanding yield and salt tolerance trade-off mechanism.

The OsSRO1c-OsDREB2B complex undergoes protein phase transition to enhance cold tolerance in rice

Cold stress is one of the major abiotic stress factors affecting rice growth and development, leading to significant yield loss in the context of global climate change. Exploring natural variants that confer cold resistance and the underlying molecular mechanism responsible for this is the major strategy to breed cold-tolerant rice varieties. Here, we show that natural variations of a SIMILAR to RCD ONE (SRO) gene, OsSRO1c, confer cold tolerance in rice at both seedling and booting stages. Our in vivo and in vitro experiments demonstrated that OsSRO1c possesses intrinsic liquid-liquid phase-separation ability and recruits OsDREB2B, an AP2/ERF transcription factor that functions as a positive regulator of cold stress, into its biomolecular condensates in the nucleus, resulting in elevated transcriptional activity of OsDREB2B. We found that the OsSRO1c-OsDREB2B complex directly responds to low temperature through dynamic phase transitions and regulates key cold-response genes, including COLD1. Furthermore, we showed that introgression of an elite haplotype of OsSRO1c into a cold-susceptible indica rice could significantly increase its cold resistance. Collectively, our work reveals a novel cold-tolerance regulatory module in rice and provides promising genetic targets for molecular breeding of cold-tolerant rice varieties.

Strigolactone-gibberellin crosstalk mediated by a distant silencer fine-tunes plant height in upland cotton

Optimal plant height is crucial in modern agriculture, influencing lodging resistance and facilitating mechanized crop production. Upland cotton (Gossypium hirsutum) is the most important fiber crop globally; however, the genetic basis underlying plant height remains largely unexplored. In this study, we conducted a genome-wide association study to identify a major locus controlling plant height (PH1) in upland cotton. This locus encodes gibberellin 2-oxidase 1A (GhPH1) and features a 1133-bp structural variation (PAVPH1) located approximately 16 kb upstream. The presence or absence of PAVPH1 influences the expression of GhPH1, thereby affecting plant height. Further analysis revealed that a gibberellin-regulating transcription factor (GhGARF) recognizes and binds to a specific CATTTG motif in both the GhPH1 promoter and PAVPH1. This interaction downregulates GhPH1, indicating that PAVPH1 functions as a distant upstream silencer. Intriguingly, we found that DWARF53 (D53), a key repressor of the strigolactone (SL) signaling pathway, directly interacts with GhGARF to inhibit its binding to targets. Moreover, we identified a previously unrecognized gibberellin-SL crosstalk mechanism mediated by the GhD53-GhGARF-GhPH1/PAVPH1 module, which is crucial for regulating plant height in upland cotton. These findings shed light on the genetic basis and gene interaction network underlying plant height, providing valuable insights for the development of semi-dwarf cotton varieties through precise modulation of GhPH1 expression.

Pseudomonas syringae pv. actinidiae Unique Effector HopZ5 Interacts with GF14C to Trigger Plant Immunity

The bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae (Psa) is the most devastating disease threatening the global kiwifruit production. This pathogen delivers multiple effector proteins into plant cells to resist plant immune responses and facilitate their survival. Here, we focused on the unique effector HopZ5 in Psa, which previously has been reported to have virulence functions. In this study, our results showed that HopZ5 could cause macroscopic cell death and trigger a serious immune response by agroinfiltration in Nicotiana benthamiana, along with upregulated expression of immunity-related genes and significant accumulation of reactive oxygen species and callose. Subsequently, we confirmed that HopZ5 interacted with the phosphoserine-binding protein GF14C in both the nonhost plant N. benthamiana (NbGF14C) and the host plant kiwifruit (AcGF14C), and silencing of NbGF14C compromised HopZ5-mediated cell death, suggesting that GF14C plays a crucial role in the detection of HopZ5. Further studies showed that overexpression of NbGF14C both markedly reduced the infection of Sclerotinia sclerotiorum and Phytophthora capsica in N. benthamiana, and overexpression of AcGF14C significantly enhanced the resistance of kiwifruit against Psa, indicating that GF14C positively regulates plant immunity. Collectively, our results revealed that the virulence effector HopZ5 could be recognized by plants and interact with GF14C to activate plant immunity.

Proxitome profiling reveals a conserved SGT1-NSL1 signaling module that activates NLR-mediated immunity

Suppressor of G2 allele of skp1 (SGT1) is a highly conserved eukaryotic protein that plays a vital role in growth, development, and immunity in both animals and plants. Although some SGT1 interactors have been identified, the molecular regulatory network of SGT1 remains unclear. SGT1 serves as a co-chaperone to stabilize protein complexes such as the nucleotide-binding leucine-rich repeat (NLR) class of immune receptors, thereby positively regulating plant immunity. SGT1 has also been found to be associated with the SKP1-Cullin-F-box (SCF) E3 ubiquitin ligase complex. However, whether SGT1 targets immune repressors to coordinate plant immune activation remains elusive. In this study, we constructed a toolbox for TurboID- and split-TurboID-based proximity labeling (PL) assays in Nicotiana benthamiana and used the PL toolbox to explore the SGT1 interactome during pre- and post-immune activation. The comprehensive SGT1 interactome network we identified highlights a dynamic shift from proteins associated with plant development to those linked with plant immune responses. We found that SGT1 interacts with Necrotic Spotted Lesion 1 (NSL1), which negatively regulates salicylic acid-mediated defense by interfering with the nucleocytoplasmic trafficking of non-expressor of pathogenesis-related genes 1 (NPR1) during N NLR-mediated response to tobacco mosaic virus. SGT1 promotes the SCF-dependent degradation of NSL1 to facilitate immune activation, while salicylate-induced protein kinase-mediated phosphorylation of SGT1 further potentiates this process. Besides N NLR, NSL1 also functions in several other NLR-mediated immunity. Collectively, our study unveils the regulatory landscape of SGT1 and reveals a novel SGT1-NSL1 signaling module that orchestrates plant innate immunity.

Effector CLas0185 targets methionine sulphoxide reductase B1 of Citrus sinensis to promote multiplication of 'Candidatus Liberibacter asiaticus' via enhancing enzymatic activity of ascorbate peroxidase 1

Citrus huanglongbing (HLB) has been causing enormous damage to the global citrus industry. As the main causal agent, 'Candidatus Liberibacter asiaticus' (CLas) delivers a set of effectors to modulate host responses, while the modes of action adopted remain largely unclear. Here, we demonstrated that CLIBASIA_00185 (CLas0185) could attenuate reactive oxygen species (ROS)-mediated cell death in Nicotiana benthamiana. Transgenic expression of CLas0185 in Citrus sinensis 'Wanjincheng' enhanced plant susceptibility to CLas. We found that methionine sulphoxide reductase B1 (CsMsrB1) was targeted by the effector, and its abundance was elevated in CLas0185-transgenic citrus plants. Their interaction promoted CLas proliferation. We then determined that CsMsrB1 sustained redox state and enzymatic activity of ascorbate peroxidase 1 (CsAPX1) under oxidative stress. The latter reduced H2O2 accumulation and was associated with host susceptibility to CLas infection. Consistently, citrus plants expressing CLas0185 and CsMsrB1 conferred enhanced APX activity and decreased H2O2 content. Taken together, these findings revealed how CLas0185 benefits CLas colonization by targeting CsMsrB1, which facilitated the antioxidant activity and depressed ROS during pathogen infection.