Leucine-rich Repeat Receptor-like Kinase Research Articles

Phytosulfokine receptor 1 (AtPSKR1) acts as a positive regulator of leaf senescence by mediating ROS signaling in Arabidopsis thaliana

Leaf senescence represents an active and regulated degeneration process. Leucine-rich repeat receptor-like protein kinase (LRR-RLK) represents a large group of cell surface receptors that play important roles in multiple biological processes, and some are also known to regulate the senescence process. In the present study, we elucidated the involvement of Phytosulfokine Receptor (PSKR) gene in the regulation of leaf senescence. The expression of PSKR1 of Arabidopsis was found to be up-regulated during leaf senescence. The over-expressing lines of AtPSKR1 and its rice homologue OsPSKR10 displayed an early leaf senescent phenotype in Arabidopsis, while the late senescence in mutant line of AtPSKR1 supported the idea that PSKR positively regulate the process of leaf senescence. Furthermore, the leaves of the overexpressing lines displayed increased superoxide accumulation compared to mutant lines, along with higher expression of NADPH oxidases (AtRBOHD and AtRBOHF). Importantly, our findings demonstrates that both AtPSKR1and OsPSKR10 interact with AtRBOHD and AtRBOHF and thereby instigating superoxide accumulation in the leaves through NADPH oxidases.

Receptor-associated kinases control the lipid provisioning program in plant-fungal symbiosis.

The mutualistic association between plants and arbuscular mycorrhizal (AM) fungi requires intracellular accommodation of the fungal symbiont and maintenance by means of lipid provisioning. Symbiosis signaling through lysin motif (LysM) receptor-like kinases and a leucine-rich repeat receptor-like kinase DOES NOT MAKE INFECTIONS 2 (DMI2) activates transcriptional programs that underlie fungal passage through the epidermis and accommodation in cortical cells. We show that two Medicago truncatula cortical cell-specific, membrane-bound proteins of a CYCLIN-DEPENDENT KINASE-LIKE (CKL) family associate with, and are phosphorylation substrates of, DMI2 and a subset of the LysM receptor kinases. CKL1 and CKL2 are required for AM symbiosis and control expression of transcription factors that regulate part of the lipid provisioning program. Onset of lipid provisioning is coupled with arbuscule branching and with the REDUCED ARBUSCULAR MYCORRHIZA 1 (RAM1) regulon for complete endosymbiont accommodation.

Phototropin2 3’UTR overlaps with the AT5G58150 gene encoding an inactive RLK kinase

BackgroundThis study examines the biological implications of an overlap between two sequences in the Arabidopsis genome, the 3’UTR of the PHOT2 gene and a putative AT5G58150 gene, encoded on the complementary strand. AT5G58150 is a probably inactive protein kinase that belongs to the transmembrane, leucine-rich repeat receptor-like kinase family. Phot2 is a membrane-bound UV/blue light photoreceptor kinase. Thus, both proteins share their cellular localization, on top of the proximity of their loci.ResultsThe extent of the overlap between 3’UTR regions of AT5G58150 and PHOT2 was found to be 66 bp, using RACE PCR. Both the at5g58150 T-DNA SALK_093781C (with insertion in the promoter region) and 35S::AT5G58150-GFP lines overexpress the AT5G58150 gene. A detailed analysis did not reveal any substantial impact of PHOT2 or AT5G58150 on their mutual expression levels in different light and osmotic stress conditions. AT5G58150 is a plasma membrane protein, with no apparent kinase activity, as tested on several potential substrates. It appears not to form homodimers and it does not interact with PHOT2. Lines that overexpress AT5G58150 exhibit a greater reduction in lateral root density due to salt and osmotic stress than wild-type plants, which suggests that AT5G58150 may participate in root elongation and formation of lateral roots. In line with this, mass spectrometry analysis identified proteins with ATPase activity, which are involved in proton transport and cell elongation, as putative interactors of AT5G58150. Membrane kinases, including other members of the LRR RLK family and BSK kinases (positive regulators of brassinosteroid signalling), can also act as partners for AT5G58150.ConclusionsAT5G58150 is a membrane protein that does not exhibit measurable kinase activity, but is involved in signalling through interactions with other proteins. Based on the interactome and root architecture analysis, AT5G58150 may be involved in plant response to salt and osmotic stress and the formation of roots in Arabidopsis.

Mutation of BAM2 rescues the sunn hypernodulation phenotype in Medicago truncatula, suggesting that a signaling pathway like CLV1/BAM in Arabidopsis affects nodule number.

The unique evolutionary adaptation of legumes for nitrogen-fixing symbiosis leading to nodulation is tightly regulated by the host plant. The autoregulation of nodulation (AON) pathway negatively regulates the number of nodules formed in response to the carbon/nitrogen metabolic status of the shoot and root by long-distance signaling to and from the shoot and root. Central to AON signaling in the shoots of Medicago truncatula is SUNN, a leucine-rich repeat receptor-like kinase with high sequence similarity with CLAVATA1 (CLV1), part of a class of receptors in Arabidopsis involved in regulating stem cell populations in the root and shoot. This class of receptors in Arabidopsis includes the BARELY ANY MERISTEM family, which, like CLV1, binds to CLE peptides and interacts with CLV1 to regulate meristem development. M. truncatula contains five members of the BAM family, but only MtBAM1 and MtBAM2 are highly expressed in the nodules 48 hours after inoculation. Plants carry mutations in individual MtBAMs, and several double BAM mutant combinations all displayed wild-type nodule number phenotypes. However, Mtbam2 suppressed the sunn-5 hypernodulation phenotype and partially rescued the short root length phenotype of sunn-5 when present in a sunn-5 background. Grafting determined that bam2 suppresses supernodulation from the roots, regardless of the SUNN status of the root. Overexpression of MtBAM2 in wild-type plants increases nodule numbers, while overexpression of MtBAM2 in some sunn mutants rescues the hypernodulation phenotype, but not the hypernodulation phenotypes of AON mutant rdn1-2 or crn. Relative expression measurements of the nodule transcription factor MtWOX5 downstream of the putative bam2 sunn-5 complex revealed disruption of meristem signaling; while both bam2 and bam2 sunn-5 influence MtWOX5 expression, the expression changes are in different directions. We propose a genetic model wherein the specific root interactions of BAM2/SUNN are critical for signaling in nodule meristem cell homeostasis in M. truncatula.

Comparative physiological and transcriptomic analysis of two contrasting soybean genotypes reveals complex mechanisms involved in drought avoidance

AbstractTo overcome drought stress in soybean (Glycine max), it is strategically vital to improve drought resistance. Yet, the underlying molecular mechanisms responsible for drought resistance remain poorly defined. Here, we present comparative physiological and transcriptome analyses in seedlings of two contrasting genotypes, drought‐resistant (DR) L14 and drought‐sensitive (DS) L21 in response to polyethylene glycol (PEG)‐induced drought stress. Each genotype was subjected to 20% PEG along with control (0% PEG) in a greenhouse, and the leave samples were collected to determine the physiological traits and transcriptome profiling. With the accumulation of abscisic acid (ABA) under drought stress, the DR genotype exhibited higher water retention capability and slow‐wilting phenotype compared to DS genotype. As nonsignificant changes in oxidative damages and antioxidant defenses, overcoming drought stress in DR genotype was facilitated by drought avoidance rather than drought tolerance. There were 1567 and 4029 differentially expressed genes (DEGs) identified in the DR and DS genotypes, respectively. The DEGs were mostly enriched in photosynthesis, carbohydrate metabolism, lipid metabolism, cell wall organization, and signaling pathways, which were less affected in DR genotype. However, most of the leucine‐rich repeat receptor‐like kinases (LRR‐RLKs) were uniquely downregulated in DS genotype but uniquely upregulated in DR genotype by drought stress. By protein–protein interaction network analysis and whole genome resequencing, six LRR‐RLKs were considered the potential candidate genes for drought avoidance. We suggested that these LRR‐RLKs may play a critical role in promoting ABA‐induced stomatal closure through enhancing ABA sensitivity, but this hypothesis needs further validation. Taken together, these findings could provide in‐depth insights into the physiological and molecular mechanisms associated with drought avoidance and facilitate the breeding of drought‐resistant soybean cultivars.

Phytosulfokine peptides, their receptors, and functions.

Phytosulfokines (PSKs) are a class of disulfated pentapeptides and are regarded as plant peptide hormones. PSK-α, -γ, -δ, and -ϵ are four bioactive PSKs that are reported to have roles in plant growth, development, and immunity. In this review, we summarize recent advances in PSK biosynthesis, signaling, and function. PSKs are encoded by precursor genes that are widespread in higher plants. PSKs maturation from these precursors requires a sulfation step, which is catalyzed by a tyrosylprotein sulfotransferase, as well as proteolytic cleavage by subtilisin serine proteases. PSK signaling is mediated by plasma membrane-localized receptors PSKRs that belong to the leucine-rich repeat receptor-like kinase family. Moreover, multiple biological functions can be attributed to PSKs, including promoting cell division and cell growth, regulating plant reproduction, inducing somatic embryogenesis, enhancing legume nodulation, and regulating plant resistance to biotic and abiotic stress. Finally, we propose several research directions in this field. This review provides important insights into PSKs that will facilitate biotechnological development and PSK application in agriculture.

Differential expansion and retention patterns of LRR-RLK genes across plant evolution.

To maximize overall fitness, plants must accurately respond to a host of growth, developmental, and environmental signals throughout their life. Many of these internal and external signals are perceived by the leucine-rich repeat receptor-like kinases, which play roles in regulating growth, development, and immunity. This largest family of receptor kinases in plants can be divided into subfamilies based on the conservation of the kinase domain, which demonstrates that shared evolutionary history often indicates shared molecular function. Here we investigate the evolutionary history of this family across the evolution of 112 plant species. We identify lineage-specific expansions of the malectin-domain containing subfamily LRR subfamily I primarily in the Brassicales and bryophytes. Most other plant lineages instead show a large expansion in LRR subfamily XII, which in Arabidopsis is known to contain key receptors in pathogen perception. This striking asymmetric expansion may reveal a dichotomy in the evolutionary history and adaptation strategies employed by plants. A greater understanding of the evolutionary pressures and adaptation strategies acting on members of this receptor family offers a way to improve functional predictions for orphan receptors and simplify the identification of novel stress-related receptors.

Isothermal Titration Calorimetry to Study Plant Peptide Ligand-Receptor Interactions.

The field of plant receptor biology has rapidly expanded in the past three decades. However, the demonstration of direct interaction between receptor-ligand pairs remains a challenge. Identifying and quantifying protein-ligand interactions is crucial for understanding how they regulate certain physiological processes. An important aspect is the quantification of different parameters of the interaction, like binding affinity, kinetics, and ligand specificity that drive the formation of signaling complexes. In this chapter, we discuss Isothermal Titration Calorimetry (ITC) as a label-free technique to measure thermodynamic parameters of ligand binding with high accuracy and reproducibility. We provide a detailed guideline how to design, perform, analyze, and interpret ITC measurements using as an example the interaction between the SCHENGEN3/GASSHO1 (SGN3/GSO1) leucine-rich repeat receptor-like kinase and its sulfated peptide ligand CASPARIAN STRIP INTEGRITY FACTOR 2 (CIF2).

Effects of D128N Mutation on OsSERK2 in Xa21-Mediated Immune Complex: An In Silico Study

Receptor-like kinases (RLKs) are plant proteins that form signaling circuits to transduce information through the plant cell membrane to the nucleus and activate processes that direct growth, development, stress response, and disease resistance. Upon sensing various environmental stress stimuli, RLKs interact with specific targets and recruit several other proteins to initiate the defense mechanism. Among many RLK subfamilies, leucine-rich repeat RLKs (LRR-RLKs) are the largest. Xa21, a member of LRR-RLK, is a vital receptor protein in rice plants that binds with bacterial RaxX21-sY, whereas OsSERK2 is a somatic embryogenic receptor kinase (SERK) that acts as a coreceptor in this process. This study focuses on the effect of a substitution mutation of aspartate128 with asparagine128 (D128N) in OsSERK2 on the interdependent binding pattern of the Xa21, RaxX21-sY, and OsSERK2 D128N proteins. The in silico results showed that the D128N mutation in OsSERK2 can significantly change the interaction pattern of the critical residues of the OsSERK2 and affects its receptor-ligand (Xa21-RaxX21-sY) interaction in the complex. These findings are expected to significantly contribute to the study of the structural basis of Xa21-mediated immunity and the first layer of plant defense mechanisms, thereby aiding further research on these structures and their phenotypic implications.

Life and death: the destiny of Phytophthora sojae determined by a receptor-like kinase

Leucine-rich repeat receptor-like kinases (LRR-RLKs) are well known to act in plant growth, development, and defense responses. Plant LRR-RLKs locate on cell surface to sense and initiate responsive signals to a variety of extracellular stimuli, such as microbe-associated molecular patterns (MAMPs) released from microorganisms. LRR-RLKs are also present in microbes and function in microbial growth and development, but their roles in communicating with hosts are largely unknown. A recent study published in Nature Communications uncovered that a microbial LRR-RLK, PsRLK6, is required for oospore development in the sexual reproduction of Phytophthora sojae, an oomycete pathogen that causes root and stem rot in soybean. Meanwhile, PsRLK6 is recognized as a novel type of MAMP by an unknown plant LRR receptor-like protein and triggers immune responses in soybean, tomato, and Nicotiana benthamiana. The findings reveal dual roles of a pathogen LRR-RLK in determining both life through sexual reproduction and death through triggering plant immunity.

Genome-wide identification of the LRR-RLK gene family in peanut and functional characterization of AhLRR-RLK265 in salt and drought stresses

Leucine-rich repeat receptor-like kinases (LRR-RLKs) play important roles in plant developmental regulations and various stress responses. Peanut (Arachis hypogaea L.) is a worldwide important oil crop; however, no systematic identification or analysis of the peanut LRR-RLK gene family has been reported. In present study, 495 LRR-RLK genes in peanut were identified and analyzed. The 495 AhLRR-RLK genes were classed into 14 groups and 10 subgroups together with their Arabidopsis homologs according to phylogenetic analyses, and 491 of 495 AhLRR-RLK genes unequally located on 20 chromosomes. Analyses of gene structure and protein motif organization revealed similarity in exon/intron and motif organization among members of the same subgroup, further supporting the phylogenetic results. Gene duplication events were found in peanut LRR-RLK gene family via syntenic analysis, which were important in LRR-RLK gene family expansion in peanut. We found that the expression of AhLRR-RLK genes was detected in different tissues using RNA-seq data, implying that AhLRR-RLK genes may differ in function. In addition, Arabidopsis plants overexpressing stress-induced AhLRR-RLK265 displayed lower seed germination rates and root lengths compared to wild-type under exogenous ABA treatment. Notably, overexpression of AhLRR-RLK265 enhanced tolerance to salt and drought stresses in transgenic Arabidopsis. Moreover, the AhLRR-RLK265-OE lines were found to have higher activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) under salt and drought stress treatments. We believe these results may provide valuable information about the function of peanut LRR-RLK genes for further analysis.

Asymmetric Evolution of Protein Domains in the Leucine-Rich Repeat Receptor-Like Kinase Family of Plant Signaling Proteins.

The coding sequences of developmental genes are expected to be deeply conserved, with cis-regulatory change driving the modulation of gene function. In contrast, proteins with roles in defense are expected to evolve rapidly, in molecular arms races with pathogens. However, some gene families include both developmental and defense genes. In these families, does the tempo and mode of evolution differ between genes with divergent functions, despite shared ancestry and structure? The leucine-rich repeat receptor-like kinase (LRR-RLKs) protein family includes members with roles in plant development and defense, thus providing an ideal system for answering this question. LRR-RLKs are receptors that traverse plasma membranes. LRR domains bind extracellular ligands; RLK domains initiate intracellular signaling cascades in response to ligand binding. In LRR-RLKs with roles in defense, LRR domains evolve faster than RLK domains. To determine whether this asymmetry extends to LRR-RLKs that function primarily in development, we assessed evolutionary rates and tested for selection acting on 11 subfamilies of LRR-RLKs, using deeply sampled protein trees. To assess functional evolution, we performed heterologous complementation assays in Arabidopsis thaliana (Arabidopsis). We found that the LRR domains of all tested LRR-RLK proteins evolved faster than their cognate RLK domains. All tested subfamilies of LRR-RLKs had strikingly similar patterns of molecular evolution, despite divergent functions. Heterologous transformation experiments revealed that multiple mechanisms likely contribute to the evolution of LRR-RLK function, including escape from adaptive conflict. Our results indicate specific and distinct evolutionary pressures acting on LRR versus RLK domains, despite diverse organismal roles for LRR-RLK proteins.

General Regulatory Factor7 regulates innate immune signalling to enhance Verticillium wilt resistance in cotton.

Sessile growing plants are always vulnerable to microbial pathogen attacks throughout their lives. To fend off pathogen invasion, plants have evolved a sophisticated innate immune system that consists of cell surface receptors and intracellular receptors. Somatic embryogenesis receptor kinases (SERKs) belong to a small group of leucine-rich repeat receptor-like kinases (LRR-RLKs) that function as co-receptors regulating diverse physiological processes. GENRAL REGULATORY FACTOR (GRF) proteins play an important role in physiological signalling transduction. However, the function of GRF proteins in plant innate immune signalling remains elusive. Here, we identified a GRF gene, GauGRF7, that is expressed both constitutively and in response to fungal pathogen infection. Intriguingly, silencing of GRF7 compromised plant innate immunity, resulting in susceptibility to Verticillium dahliae infection. Both transgenic GauGRF7 cotton and transgenic GauGRF7 Arabidopsis lines enhanced the innate immune response to V. dahliae infection, leading to high expression of two helper NLRs (hNLR) genes (ADR1 and NRG1) and pathogenesis-related genes, and increased ROS production and salicylic acid level. Moreover, GauGRF7 interacted with GhSERK1, which positively regulated GRF7-mediated innate immune response in cotton and Arabidopsis. Our findings revealed the molecular mechanism of the GRF protein in plant immune signaling and offer potential opportunities for improving plant resistance to V. dahliae infection.

Knocking Out OsRLK7-1 Impairs Rice Growth and Development but Enhances Its Resistance to Planthoppers.

Leucine-rich repeat receptor-like kinases (LRR-RLKs) are an important subfamily of receptor-like kinases (RLKs) in plants that play key roles in sensing different biotic and abiotic stress. However, the role of LRR-RLKs in herbivore-induced plant defense remains largely elusive. Here, we found that the expression of a rice gene, OsRLK7-1, was induced by mechanical wounding, but was slightly suppressed by the infestation of gravid females of brown planthopper (BPH, Nilaparvata lugens) or white-backed planthopper (WBPH, Sogatella furcifera). Through targeted disruption of OsRLK7-1 (resulting in the ko-rlk lines), we observed an augmentation in transcript levels of BPH-induced OsMPK3, OsWRKY30, OsWRKY33, and OsWRKY45, alongside heightened levels of planthopper-induced jasmonic acid, JA-isoleucine, and abscisic acid in plant tissues. These dynamic changes further facilitated the biosynthesis of multiple phenolamides within the rice plants, culminating in an enhanced resistance to planthopper infestations under both lab and field conditions. In addition, knocking out OsRLK7-1 impaired plant growth and reproduction. These results suggest that OsRLK7-1 plays an important role in regulating rice growth, development, and rice-planthopper interactions.

ORYZA SATIVA SPOTTED-LEAF 41 (OsSPL41) Negatively Regulates Plant Immunity in Rice

Identification of immunity-associated leucine-rich repeat receptor-like protein kinases (LRR-RLK) is critical to elucidate the LRR-RLK mediated mechanism of plant immunity. Here, we reported the map-based cloning of a novel rice SPOTTED-LEAF 41 (OsSPL41) encoding a putative LRR-RLK protein (OsLRR-RLK41/OsSPL41) that regulated disease responses to the bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). An 8-bp insertion at position 865 bp in a mutant spotted-leaf 41 (spl41) allele led to the formation of purple-brown lesions on leaves. Functional complementation by the wild type allele (OsSPL41) can rescue the mutant phenotype, and the complementary lines showed similar performance to wild type in a number of agronomic, physiological and molecular indices. OsSPL41 was constitutively expressed in all tissues tested, and OsSPL41 contains a typical transmembrane domain critical for its localization to the cell membrane. The mutant exhibited an enhanced level of resistance to Xoo in companion of markedly up-regulated expression of pathogenesis-related genes such as OsPR10a, OsPAL1 and OsNPR1, while the level of salicylic acid was significantly increased in spl41. In contrast, the over-expression lines exhibited a reduced level of H2O2 and were much susceptible to Xoo with down-regulated expression of pathogenesis-related genes. These results suggested that OsSPL41 might negatively regulate plant immunity through the salicylic acid signaling pathway in rice.

A Phytophthora receptor-like kinase regulates oospore development and can activate pattern-triggered plant immunity

Plant cell-surface leucine-rich repeat receptor-like kinases (LRR-RLKs) and receptor-like proteins (LRR-RLPs) form dynamic complexes to receive a variety of extracellular signals. LRR-RLKs are also widespread in oomycete pathogens, whereas it remains enigmatic whether plant and oomycete LRR-RLKs could mediate cell-to-cell communications between pathogen and host. Here, we report that an LRR-RLK from the soybean root and stem rot pathogen Phytophthora sojae, PsRLK6, can activate typical pattern-triggered immunity in host soybean and nonhost tomato and Nicotiana benthamiana plants. PsRLK6 homologs are conserved in oomycetes and also exhibit immunity-inducing activity. A small region (LRR5-6) in the extracellular domain of PsRLK6 is sufficient to activate BAK1- and SOBIR1-dependent immune responses, suggesting that PsRLK6 is likely recognized by a plant LRR-RLP. Moreover, PsRLK6 is shown to be up-regulated during oospore maturation and essential for the oospore development of P. sojae. Our data provide a novel type of microbe-associated molecular pattern that functions in the sexual reproduction of oomycete, and a scenario in which a pathogen LRR-RLK could be sensed by a plant LRR-RLP to mount plant immunity.

A Ceratopteris EXCESS MICROSPOROCYTES1 suppresses reproductive transition in the fern vegetative leaves

Land plant sexual reproduction involves the transition of cells from somatic to reproductive identity during post-embryonic development. In Arabidopsis, the leucine-rich repeat receptor-like kinase EXCESS MICROSPOROCYTES1 (EXS/EMS1) restricts the number of sporogenous cells during the transition from diploid tissue to haploid spore production by promoting the formation of the tapetum cell layer within the anther. Although all land plants studied contain EMS1 genes, its function is unknown beyond a few angiosperms. In the model fern Ceratopteris (Ceratopteris richardii), we discovered an EMS1 homolog (CrEMS1) that functions to suppress formation of reproductive structures on vegetative leaves of the fern sporophyte, a role not found in angiosperms. Suppression of CrEMS1 by RNAi did not affect sporogenesis on reproductive leaves but did affect antheridium production of the fern gametophyte. Expression patterns of CrEMS1 across developmental stages suggest threshold levels of CrEMS1 control the specification of reproductive organs during both generations of the fern. Additional EMS1 homologs present in the fern genome suggest a dynamic role of EMS1 receptors in the evolution of reproductive development in vascular plants.

A glycoside hydrolase 12 protein from Cytospora chrysosperma triggers plant immunity but is not essential to virulence

Phytopathogens secrete numerous effectors that facilitate their infection and colonization processes. However, the pathogenic mechanism of effectors in Cytospora chrysosperma, the causal agent of canker disease in many woody plants, remains poorly understood. In this study, we identified five glycoside hydrolase family 12 (GH12) effector genes in C. chrysosperma genome, all of which were significantly upregulated during the infection stages. Among them, CcEG1, which contains an additional carbohydrate-binding module family 1 domain (CBM1) at the C-terminal, was selected for further analysis. Transient expression studies showed that CcEG1 was localized to the apoplastic region of Nicotiana benthamiana and acted as an elicitor to induce cell death, and activate the expression of genes involved in salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) signaling pathways. Furthermore, the GH12 domain (position 43–249) was sufficient for cell death-inducing activity, rather than the CBM1 domain. Additionally, the leucine-rich repeat (LRR) receptor-like kinases NbBAK1 and NbSOBIR1 were required for defense responses triggered by CcEG1. Intriguingly, deletion of CcEG1 did not affect fungal pathogenicity, growth, response to hydrogen peroxide and cell wall integrity agents, but affected cellulase utilization. In conclusion, our results suggest that CcEG1 induces coreceptors NbBAK1- and NbSOBIR1- dependent plant immunity, increasing our understanding about fungal pathogenesis during the interaction between C. chrysosperma and its host.

An Ustilaginoidea virens glycoside hydrolase 42 protein is an essential virulence factor and elicits plant immunity as a PAMP.

Rice false smut, caused by the ascomycete fungus Ustilaginoidea virens, which infects rice florets before heading, severely threatens rice grain yield and quality worldwide. The U. virens genome encodes a number of glycoside hydrolase (GH) proteins. So far, the functions of these GHs in U. virens are largely unknown. In this study, we identified a GH42 protein secreted by U. virens, named UvGHF1, that exhibits β-galactosidase activity. UvGHF1 not only functions as an essential virulence factor during U. virens infection, but also serves as a pathogen-associated molecular pattern (PAMP) in Nicotiana benthamiana and rice. The PAMP activity of UvGHF1 is independent of its β-galactosidase activity. Moreover, UvGHF1 triggers cell death in N. benthamiana in a BAK1-dependent manner. Ectopic expression of UvGHF1 in rice induces pattern-triggered immunity and enhances rice resistance to fungal and bacterial diseases. RNA-seq analysis revealed that UvGHF1 expression in rice not only activates expression of many defence-related genes encoding leucine-rich repeat receptor-like kinases and WRKY and ERF transcription factors, but also induces diterpenoid biosynthesis and phenylpropanoid biosynthesis pathways. Therefore, UvGHF1 contributes to U. virens virulence, but is also recognized by the rice surveillance system to trigger plant immunity.

PSW1, an LRR receptor kinase, regulates pod size in peanut.

Pod size is a key agronomic trait that greatly determines peanut yield, the regulatory genes and molecular mechanisms that controlling peanut pod size are still unclear. Here, we used quantitative trait locus analysis to identify a peanut pod size regulator, POD SIZE/WEIGHT1 (PSW1), and characterized the associated gene and protein. PSW1 encoded leucine-rich repeat receptor-like kinase (LRR-RLK) and positively regulated pod stemness. Mechanistically, this allele harbouring a 12-bp insertion in the promoter and a point mutation in the coding region of PSW1 causing a serine-to-isoleucine (S618I) substitution substantially increased mRNA abundance and the binding affinity of PSW1 for BRASSINOSTEROID INSENSITIVE1-ASSOCIATED RECEPTOR KINASE 1 (BAK1). Notably, PSW1HapII (super-large pod allele of PSW1) expression led to up-regulation of a positive regulator of pod stemness PLETHORA 1 (PLT1), thereby resulting in larger pod size. Moreover, overexpression of PSW1HapII increased seed/fruit size in multiple plant species. Our work thus discovers a conserved function of PSW1 that controls pod size and provides a valuable genetic resource for breeding high-yield crops.