A glycine-rich nuclear effector VdCE51 of Verticillium dahliae suppresses plant immune responses by inhibiting the accumulation of GhTRXH2

Verticillium dahliae is an important soil-borne fungal pathogen that causes great yield losses in many cash crops.Effectors of this fungus are known to regulate plant immunity but the mechanism much remains unclear.A glycine-rich nuclear effector,VdCE51,was able to suppress immune responses in tobacco against Botrytis cinerea and Sclerotinia sclerotiorum.This effector was a required factor for full virulence of V.dahliae,and its nuclear localization was a requisite for suppressing plant immunity.The thioredoxin GhTRXH2,identified as a positive regulator of plant immunity,was a host target of VdCE51.Our findings show a virulence regulating mechanism whereby the secreted nuclear effector VdCE51 interferes with the transcription of PR genes,and the SA signaling pathway by inhibiting the accumulation of GhTRXH2,thus suppressing plant immunity.

The IDD Transcription Factors:Their Functions in Plant Development and Environmental Response

INDETERMINATE-DOMAIN proteins(IDDs)are a plant-specific transcription factor family characterized by a conserved ID domain with four zinc finger motifs.Previous studies have demonstrated that IDDs coordinate a diversity of physiological processes and functions in plant growth and development,including floral transition,plant architecture,seed and root development,and hormone signaling.In this review,we especially summarized the latest knowledge on the functions and working models of IDD members in Arabidopsis,rice,and maize,particularly focusing on their role in the regulatory network of biotic and abiotic environmental responses,such as gravity,temperature,water,and pathogens.Understanding these mechanisms underlying the function of IDD proteins in these processes is important for improving crop yields by manipulating their activity.Overall,the review offers valuable insights into the functions and mechanisms of IDD proteins in plants,providing a foundation for further research and potential applications in agriculture.

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(Os SPL41) encoding a putative LRR-RLK protein(Os LRR-RLK41/Os SPL41) 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(Os SPL41) can rescue the mutant phenotype,and the complementary lines showed similar performance to wild type in a number of agronomic,physiological and molecular indices.Os SPL41 was constitutively expressed in all tissues tested,and Os SPL41 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 Os PR10a,Os PAL1 and Os NPR1,while the level of salicylic acid was significantly increased in spl41.In contrast,the over-expression lines exhibited a reduced level of H_(2)O_(2) and were much susceptible to Xoo with down-regulated expression of pathogenesis-related genes.These results suggested that Os SPL41 might negatively regulate plant immunity through the salicylic acid signaling pathway in rice.

A Meloidogyne incognita effector Minc03329 suppresses plant immunity and promotes parasitism

Meloidogyne incognita is a devastating plant-parasitic nematode.Effectors play important roles during the stages of nematodes infection and parasitism,but their molecular functions remain largely unknown.In this study,we characterized a new effector,Minc03329,which contains signal peptide for secretion and a C-type lectin domain.The yeast signal sequence trap experiments indicated that the signal peptide of Minc03329 is functional.In situ hybridization showed that Minc03329 was specifically expressed in the subventral esophageal gland.Real-time qPCR confirmed that the expression level of Minc03329 transcript was significantly increased in pre-parasitic and parasitic second-stage juveniles(pre-J2s and par-J2s).Tobacco rattle virus(TRV)-mediated gene silencing of Minc03329 in host plants largely reduced the pathogenicity of nematodes.On the contrary,ectopic expression of Minc03329 in Arabidopsis thaliana significantly increased plant susceptibility to nematodes.Transient expression of Minc03329 in Nicotiana benthamiana leaves suppressed the programmed cell death triggered by the pro-apoptotic protein BAX.Moreover,the transcriptome analysis of Minc03329-transgenic Arabidopsis and wild type revealed that many defense-related genes were significantly down-regulated.Interestingly,some different expressed genes were involved in the formation of nematode feeding sites.These results revealed that Minc03329 is an important effector for M.incognita,suppressing host defense response and promoting pathogenicity.

Global characterization of OsPIP aquaporins reveals that the H_(2)O_(2)transporter OsPIP2;6 increases resistance to rice blast

Plasma membrane intrinsic proteins(PIPs)are conserved plant aquaporins that transport small molecules across the plasma membrane to trigger instant stress responses and maintain cellular homeostasis under biotic and abiotic stress.To elucidate their roles in plant immunity to pathogen attack,we characterized the expression patterns,subcellular localizations,and H_(2)O_(2)-transport ability of 11 OsPIPs in rice(Oryza sativa),and identified OsPIP2;6 as necessary for rice disease resistance.OsPIP2;6 resides on the plasma membrane and facilitates cytoplasmic import of the immune signaling molecule H_(2)O_(2).Knockout of OsPIP2;6 increases rice susceptibility to Magnaporthe oryzae,indicating a positive function in plant immunity.OsPIP2;6 interacts with OsPIP2;2,which has been reported to increase rice resistance to pathogens via H_(2)O_(2)transport.Our findings suggest that OsPIP2;6 cooperates with OsPIP2;2 as a defense signal transporter complex during plant–pathogen interaction.

Eureka lemon zinc finger protein ClDOF3.4 interacts with citrus yellow vein clearing virus coat protein to inhibit viral infection

Citrus yellow vein clearing virus(CYVCV)is a new citrus virus that has become an important factor restricting the development of China’s citrus industry,and the CYVCV coat protein(CP)is associated with viral pathogenicity.In this study,the Eureka lemon zinc finger protein(ZFP)ClDOF3.4 was shown to interact with CYVCV CP in vivo and in vitro.Transient expression of ClDOF3.4 in Eureka lemon induced the expression of salicylic acid(SA)-related and hypersensitive response marker genes,and triggered a reactive oxygen species burst,ion leakage necrosis,and the accumulation of free SA.Furthermore,the CYVCV titer in ClDOF3.4 transgenic Eureka lemon plants was approximately 69.4%that in control plants 6 mon after inoculation,with only mild leaf chlorotic spots observed in those transgenic plants.Taken together,the results indicate that ClDOF3.4 not only interacts with CP but also induces an immune response in Eureka lemon by inducing the SA pathways.This is the first report that ZFP is involved in the immune response of a citrus viral disease,which provides a basis for further study of the molecular mechanism of CYVCV infection.

Popularization and Application of Haidaosu(5% Amino-oligosaccharin)as a Plant Immunity Inducer in Main Crops Cultured by Corps

The plant immunity inducer, amino-oligosaccharin, has remarkable effects in disease resistance, cold tolerance, growth promotion, yield increase and quality improvement. This paper introduced the action mechanism of amino-oligosaccharin, its main application effects on crops and application techniques. In 2013-2014, ex- periments were conducted on a variety of crops at multiple locations by Xinjiang Corps as well as popularization and application in 2013-2014, and it was shown by the popularization and application that the application of amino-oligosaccharin could promote plant growth, reduce the incidence of crop diseases and improve crop yield and product quality.

Recent advances in plant immunity with cell death:A review

Cell death is an important physiological phenomenon in life.It can be programmed or unprogrammed.Unprogrammed cell death is usually induced by abiotic or biotic stress.Recent studies have shown that many proteins regulate both cell death and immunity in plants.Here,we provide a review on the advances in plant immunity with cell death,especially the molecular regulation and underlying mechanisms of those proteins involved in both cell death and plant immunity.In addition,we discuss potential approaches toward improving plant immunity without compromising plant growth.

From molecule to cell:the expanding frontiers of plant immunity

In recent years,the field of plant immunity has witnessed remarkable breakthroughs.During the co-evolution between plants and pathogens,plants have developed a wealth of intricate defense mechanisms to safeguard their survival.Newly identified immune receptors have added unexpected complexity to the surface and intracellular sensor networks,enriching our understanding of the ongoing plant–pathogen interplay.Deciphering the molecular mechanisms of resistosome shapes our understanding of these mysterious molecules in plant immunity.Moreover,technological innovations are expanding the horizon of the plant–pathogen battlefield into spatial and temporal scales.While the development provides new opportunities for untangling the complex realm of plant immunity,challenges remain in uncovering plant immunity across spatiotemporal dimensions from both molecular and cellular levels.

Near-infrared light and PIF4 promote plant antiviral defense by enhancing RNA interference

The molecular mechanism underlying phototherapy and light treatment,which utilize various wavelength spectra of light,including near-infrared(NIR),to cure human and plant diseases,is obscure.Here we re-vealed that NIR light confers antiviral immunity by positively regulating PHYTOCHROME-INTERACTING FACTOR 4(PIF4)-activated RNA interference(RNAi)in plants.PIF4,a central transcription factor involved in light signaling,accumulates to high levels under NIR light in plants.PIF4 directly induces the transcription of two essential components of RNAi,RNA-DEPENDENT RNA POLYMERASE 6(RDR6)and ARGONAUTE 1(AGO1),which play important roles in resistance to both DNA and RNA viruses.Moreover,the pathogenic determinant bC1 protein,which is evolutionarily conserved and encoded by betasatellites,interacts with PIF4 and inhibits its positive regulation of RNAi by disrupting PIF4 dimerization.Thesefindings shed light on the molecular mechanism of PIF4-mediated plant defense and provide a new perspective for the explo-ration of NIR antiviral treatment.

Egg-associated secretions from the brown planthopper(Nilaparvata lugens)activate rice immune responses

The brown planthopper(BPH,Nilaparvata lugens)is a notorious sap-sucking insect pest that damages rice(Oryza sativa)plants throughout Asia.During BPH feeding,saliva enters rice plant tissues,whereas during oviposition egg-associated secretions(EAS)are deposited in damaged plant tissue.Dynamic changes in rice to planthopper salivary effectors have been widely reported.However,the effects of EAS from planthopper on rice immunity remains largely unexplored.In this study,we found that both infestation of rice by gravid BPH female adults and treatment with the EAS elicited a strong and rapid accumulation of jasmonic acid(JA),JA-isoleucine,and hydrogen peroxide in rice.EAS enhanced plant defenses not only in rice but also in tobacco,and these impaired the performance of BPH on rice,as well as the performance of aphids and whiteflies on tobacco.High-throughput proteome sequencing of EAS led to 110 proteins being identified and 53 proteins with 2 or more unique peptides being detected.Some proteins from BPH EAS were also found in the salivary proteome from herbivores,suggesting potential evolutionary conservation of effector functions across feeding and oviposition;however,others were only identified in EAS,and these are likely specifically related to oviposition.These findings point to novel proteins affecting interactions between planthoppers and rice during oviposition,providing an additional source of information for effector studies.

Pull the fuzes:Processing protein precursors to generate apoplastic danger signals for triggering plant immunity

The apoplast is one of the first cellular compartments outside the plasma membrane encountered by phytopathogenic microbes in the early stages of plant tissue invasion.Plants have developed sophisticated surveillance mechanisms to sense danger events at the cell surface and promptly activate immunity.However,a fine tuning of the activation of immune pathways is necessary to mount a robust and effective defense response.Several endogenous proteins and enzymes are synthesized as inactive precursors,and their post-translational processing has emerged as a critical mechanism for triggering alarms in the apoplast.In this review,we focus on the precursors of phytocytokines,cell wall remodeling enzymes,and proteases.The physiological events that convert inactive precursors into immunomodulatory active peptides or enzymes are described.This review also explores the functional synergies among phytocytokines,cell wall damage-associated molecular patterns,and remodeling,highlighting their roles in boosting extracellular immunity and reinforcing defenses against pests.

New insight into Ca^(2+)-permeable channel in plant immunity

Calcium ions(Ca^(2+)) are crucial intracellular second messengers in eukaryotic cells. Upon pathogen perception, plants generate a transient and rapid increase in cytoplasmic Ca^(2+)levels, which is subsequently decoded by Ca^(2+)sensors and effectors to activate downstream immune responses. The elevation of cytosolic Ca^(2+)is commonly attributed to Ca^(2+)influx mediated by plasma membranelocalized Ca^(2+)–permeable channels. However, the contribution of Ca^(2+)release triggered by intracellular Ca^(2+)-permeable channels in shaping Ca^(2+)signaling associated with plant immunity remains poorly understood. This review discusses recent advances in understanding the mechanism underlying the shaping of Ca^(2+)signatures upon the activation of immune receptors, with particular emphasis on the identification of intracellular immune receptors as non-canonical Ca^(2+)-permeable channels. We also discuss the involvement of Ca^(2+)release from the endoplasmic reticulum in generating Ca^(2+)signaling during plant immunity.

Decomposition of dynamic transcriptomic responses during effector-triggered immunity reveals conserved responses in two distinct plant cell populations

Rapid plant immune responses in the appropriate cells are needed for effective defense against pathogens.Although transcriptome analysis is often used to describe overall immune responses,collection of transcriptome data with sufficient resolution in both space and time is challenging.We reanalyzed public Arabidopsis time-course transcriptome data obtained after low-dose inoculation with a Pseudomonas syringae strain expressing the effector AvrRpt2,which induces effector-triggered immunity in Arabidopsis.Double-peak time-course patterns are prevalent among thousands of upregulated genes.We implemented a multicompartment modeling approach to decompose the double-peak pattern into two single-peak patterns for each gene.The decomposed peaks reveal an“echoing”pattern:the peak times of the first and second peaks correlate well across most upregulated genes.We demonstrated that the two peaks likely represent responses of two distinct cell populations that respond either cell autonomously or indirectly to AvrRpt2.Thus,the peak decomposition has extracted spatial information from the time-course data.The echoing pattern also indicates a conserved transcriptome response with different initiation times between the two cell populations despite different elicitor types.A gene set highly overlapping with the conserved gene set is also upregulated with similar kinetics during pattern-triggered immunity.Activation of a WRKY network via different entry-point WRKYs can explain the similar but not identical transcriptome responses elicited by different elicitor types.We discuss potential benefits of the properties of the WRKY activation network as an immune signaling network in light of pressure from rapidly evolving pathogens.

A novel chorismate mutase effector secreted from root-knot nematode Meloidogyne enterolobii manipulates plant immunity to promote parasitism

Meloidogyne spp.is an economically important plant-parasitic nematode distributed worldwide.To fight with host immune system for successful parasitism,plant parasitic nematodes secrete effectors to promote infection.In this study,we identified one chorismate mutase(CM)effector from M.enterolobii,named Me-CM.Spatial and temporal expression assays exhibited Me-cm is expressed in esophageal glands and up-regulated at parasitic-stage juveniles.Me-CM affects the pathogenicity of M.enterolobii based on the reduced infection rate,number of galls,egg masses,eggs per mass and multiplication rate collected from RNA silencing experiments.We showed that Me-CM localized in the cytoplasm and nucleus of plant cells and decreased the expression level of the marker gene PR1 of salicylic acid(SA)pathway.Besides,constitutive expression of Me-cm in Arabidopsis thaliana significantly reduced salicylic acid concentration.These results suggested that M.enterolobii may secrete effector Me-CM to fight with plantimmunesystemsvia regulating SA signaling pathway when interacting with host plants,ultimately facilitating parasitism.

Structure, biochemical function, and signaling mechanism of plant NLRs

To counter pathogen invasion,plants have evolved a large number of immune receptors,including membrane-resident pattern recognition receptors(PRRs)and intracellular nucleotide-binding and leucine-rich repeat receptors(NLRs).Our knowledge about PRR and NLR signaling mechanisms has expanded significantly over the past few years.Plant NLRs form multi-protein complexes called resistosomes in response to pathogen effectors,and the signaling mediated by NLR resistosomes converges on Ca2+-permeable channels.Ca2+-permeable channels important for PRR signaling have also been identified.These findings highlight a crucial role of Ca2+in triggering plant immune signaling.In this review,we first discuss the structural and biochemical mechanisms of non-canonical NLR Ca2+channels and then summarize our knowledge about immune-related Ca2+-permeable channels and their roles in PRR and NLR signaling.We also discuss the potential role of Ca2+in the intricate interaction between PRR and NLR signaling.

Epigenetic regulation of plant immunity:from chromatin codes to plant disease resistance

Facing a deteriorating natural environment and an increasing serious food crisis,bioengineering-based breeding is increasing in importance.To defend against pathogen infection,plants have evolved multiple defense mechanisms,including pathogen-associated molecular pattern(PAMP)-triggered immunity(PTI)and effector-triggered immunity(ETI).A complex regulatory network acts downstream of these PTI and ETI pathways,including hormone signal transduction and transcriptional reprogramming.In recent years,increasing lines of evidence show that epigenetic factors act,as key regulators involved in the transcriptional reprogramming,to modulate plant immune responses.Here,we summarize current progress on the regulatory mechanism of DNA methylation and histone modifications in plant defense responses.In addition,we also discuss the application of epigenetic mechanism-based resistance strategies in plant disease breeding.

Specialized metabolites as versatile tools in shaping plant-microbe associations

Plants are rich repository of a large number of chemical compounds collectively referred to as specialized metabolites.These compounds are of importance for adaptive processes including responses against changing abiotic conditions and interactions with various co-existing organisms.One of the strikingly affirmed functions of these specialized metabolites is their involvement in plants’life-long interactions with complex multi-kingdom microbiomes including both beneficial and harmful microorganisms.Recent developments in genomic and molecular biology tools not only help to generate well-curated information about regulatory and structural components of biosynthetic pathways of plant specialized metabolites but also to create and screen mutant lines defective in their synthesis.In this review,we have comprehensively surveyed the function of these specialized metabolites and discussed recent research findings demonstrating the responses of various microbes on tested mutant lines having defective biosynthesis of particular metabolites.In addition,we attempt to provide key clues about the impact of these metabolites on the assembly of the plant microbiome by summarizing the major findings of recent comparative metagenomic analyses of available mutant lines under customized and natural microbial niches.Subsequently,we delineate benchmark initiatives that aim to engineer or manipulate the biosynthetic pathways to produce specialized metabolites in heterologous systems but also to diversify their immune function.While denoting the function of these metabolites,we also discuss the critical bottlenecks associated with understanding and exploiting their function in improving plant adaptation to the environment.

RALF22 promotes plant immunity and amplifies the Pep3 immune signal

Rapid alkalinization factors(RALFs)in plants have been reported to dampen pathogenassociated molecular pattern(PAMP)-triggered immunity via suppressing PAMP-induced complex formation between the pattern recognition receptor(PRR)and its co-receptor BAK1.However,the direct and positive role of RALFs in plant immunity remains largely unknown.Herein,we report the direct and positive roles of a typical RALF,RALF22,in plant immunity.RALF22alone directly elicited a variety of typical immune responses and triggered resistance against the devastating necrotrophic fungal pathogen Sclerotinia sclerotiorum in a FERONIA(FER)-dependent manner.LORELEI(LRE)-like glycosylphosphatidylinositol(GPI)-anchored protein 1(LLG1)and NADPH oxidase RBOHD were required for RALF22-elicited reactive oxygen species(ROS)generation.The mutation of cysteines conserved in the C terminus of RALFs abolished,while the constitutive formation of two disulfide bridges between these cysteines promoted the RALF22-elicited ROS production and resistance against S.sclerotiorum,demonstrating the requirement of these cysteines in the functions of RALF22 in plant immunity.Furthermore,RALF22 amplified the Pep3-induced immune signal by dramatically increasing the abundance of PROPEP3 transcript and protein.Supply with RALF22 induced resistance against S.sclerotiorum in Brassica crop plants.Collectively,our results reveal that RALF22 triggers immune responses and augments the Pep3-induced immune signal in a FER-dependent manner,and exhibits the potential to be exploited as an immune elicitor in crop protection.

CRISPR/Cas9-Targeted Knockout of Rice Susceptibility Genes OsDjA2 and OsERF104 Reveals Alternative Sources of Resistance to Pyricularia oryzae

Rice genes OsDjA2 and OsERF104,encoding a chaperone protein and an APETELA2/ethylene-responsive factor,respectively,are strongly induced in a compatible interaction with blast fungus,and also have function in plant susceptibility validated through gene silencing.Here,we reported the CRISPR/Cas9 knockout of OsDjA2 and OsERF104 genes resulting in considerable improvement of blast resistance.A total of 15 OsDjA2(62.5%)and 17 OsERF104(70.8%)T_(0)transformed lines were identified from 24 regenerated plants for each target and used in downstream experiments.Phenotyping of homozygous T1 mutant lines revealed not only a significant decrease in the number of blast lesions but also a reduction in the percentage of diseased leaf area,compared with the infected control plants.Our results supported CRISPR/Cas9-mediated target mutation in rice susceptibility genes as a potential and alternative breeding strategy for building resistance to blast disease.