ZmDRR206 functions in maintaining cell wall integrity during maize seedling growth and defense response to external stresses

Plants adaptively change their cell wall composition and structure during their growth,development,and interactions with environmental stresses.Dirigent proteins(DIRs)contribute to environmental adaptations by dynamically reorganizing the cell wall and/or by generating defense compounds.A maize DIR,ZmDRR206,was previously reported to play a dominant role in regulation of storage nutrient accumulation in endosperm during maize kernel development.Here we show that ZmDRR206 mediates maize seedling growth and disease resistance by coordinately regulating biosynthesis of cell wall components for cell-wall integrity(CWI)maintenance.Expression of ZmDRR206 was induced in maize seedlings upon pathogen infection.ZmDRR206 overexpression in maize resulted in reduced seedling growth and photosynthetic activity but increased disease resistance and drought tolerance,revealing a tradeoff between growth and defense.Consistently,ZmDRR206 overexpression reduced the contents of primary metabolites and down-regulated genes involved in photosynthesis,while increasing the contents of major cell wall components,defense phytohormones,and defense metabolites,and up-regulated genes involved in defense and cell-wall biosynthesis in seedlings.ZmDRR206-overexpressing seedlings were resistant to cell-wall stress imposed by isoxaben,and ZmDRR206 physically interacted with ZmCesA10,which is a cellulose synthase unit.Our findings suggest a mechanism by which ZmDRR206 coordinately regulates biosynthesis of cell-wall components for CWI maintenance during maize seedling growth,and might be exploited for breeding strong disease resistance in maize.

Role of the Arabidopsis thafiana NAC transcription factors ANAC019 and ANAC055 in regulating jasmonic acid-signaled defense responses

Jasmonic acid （JA） is an important phytohormone that regulates plant defense responses against herbivore attack, pathogen infection and mechanical wounding. In this report, we provided biochemical and genetic evidence to show that the Arabidopsis thaliana NAC family proteins ANAC019 and ANAC055 might function as transcription activators to regulate JA-induced expression of defense genes. The role of the two NAC genes in JA signaling was examined with the anacO19 anac055 double mutant and with transgenic plants overexpressing ANACO19 or ANAC055. The anacO19 anac055 double mutant plants showed attenuated JA-induced VEGETATIVE STORAGE PROTEIN1 （VSP1） and LIPOXYGENASE2 （LOX2） expression, whereas transgenic plants overexpressing the two NAC genes showed enhanced JA-induced VSP1 and LOX2 expression. That the JA-induced expression of the two NAC genes depends on the function of COIl and AtMYC2, together with the finding that overexpression of ANACO19 partially rescued the JA-related phenotype of the atmyc2-2 mutant, has led us to a hypothesis that the two NAC proteins act downstream of AtMYC2 to regulate JA-signaled defense responses. Further evidence to substantiate this idea comes from the observation that the response of the anacO19 anac055 double mutant to a necrotrophic fungus showed high similarity to that of the atmyc2-2 mutant.

Evidences for involvement of endogenous cAMP in Arabidopsis defense responses to Verticillium toxins

Although there were reports suggesting the involvement of endogenous cAMP in plant defense signaling cascades, there is no direct evidence supporting this notion yet and the detailed mechanism is unclear. In the present study, we have used pathogenic fungi Verticillium dahliae and Arabidopsis plants as a model system of plant-microb interaction to demonstrate the function of endogenous cAMP in Arabidopsis defense responses. Both V. dahliae inoculation and Verticillium toxins injection induced typical “wilt” symptoms in Arabidopsis seedlings. When either 8-Br-AMP (a membrane permeable cAMP analogue) or salicylic acid (SA) was applied to Arabidopsis, the plants became resistant to V. dahliae toxins. However, addition of 8-Br-AMP did not increase the resistance of Arabidopsis transgenic plants deficient in SA to the toxins, suggesting that cAMP might act upstream of SA in plant defense signaling pathway. Indeed, 8-Br-cAMP and forskolin, an activator of adenylyl cyclase, significantly stimulated the endogenous SA level in plants, whereas DDA, an inhibitor of adenylyl cyclase dramatically reduced toxin-induced SA increase. Both the endog- enous cAMP and SA increased significantly in Arabidopsis seedlings treated with toxins. Furthermore, transcription level of pathogenesis-related protein 1 gene (PR1) was strongly induced by both 8-Br-cAMP and the toxin treatment. Taken together, our data demonstrate that endogenous cAMP is involved in plant defense responses against Verticillium- secreted toxins by regulating the production of the known signal SA in plant defense pathway.

Jasmonic acid and ethylene signaling pathways participate in the defense response of Chinese cabbage to Pectobacterium carotovorum infection

Chinese cabbage(Brassica rapa subsp.pekinensis)suffers from soft rot disease caused by Pectobacterium carotovorum(Pc).To uncover the mechanisms underlying the defense response of Chinese cabbage to Pc,we constructed a suppression subtractive hybridization(SSH)library from Pc-infected cabbage and obtained 1919 non-redundant expressed sequence tags(ESTs),which were used for cDNA microarray.We detected 800 differentially expressed genes(DEGs)in cabbage at different time points post-Pc inoculation,which were further confirmed by quantitative real-time PCR.One quarter of these DEGs were involved in the biotic stress pathways visualized by MapMan.Among them,8,8,1,3,and 2 DEGs were related to jasmonic acid(JA),ethylene(ET),JA+ET,auxin,and abscisic acid(ABA)signaling pathways,respectively,while no DEG was detected for salicylic acid(SA)signaling.Assessment of phytohormone production in the Pc-infected leaves showed that JA and ET production was increased,while SA production was decreased.Treatment with JA,methyl jasmonate(MeJA),the ET precursor 1-aminocyclopropane-1-carboxylate(ACC),or combinations thereof,reduced the disease severity,and the JA and JA+ACC treatments were superior and performed equally well.Our findings suggest that JA and ET may act synergistically against Pc infection in Chinese cabbage,and JA-mediated signaling might be the most significant.

Host Active Defense Responses Occur within 24 Hours after Pathogen Inoculation in the Rice Blast System

Phenotypical, cytological and molecular responses of rice to the fungus Magnaporthe grisea were studied using rice cultivars and lesion mimic plants. The cultivar Katy was susceptible to several virulent M. grisea isolates, and a Sekiguchi like-lesion mimic mutant of Katy （LmmKaty） showed enhanced resistance to these isolates. Lesion mimic phenotype of LmmKaty was rapidly induced by virulent M. grisea isolates or by avirulent ones only at high levels of inoculum. Autofluorescence （a sign of an active defense response） was visible under ultraviolet light 24 h after localized inoculation in the incompatible interaction, whereas, not evident in the compatible interaction. Autofluorescence was also observed in LmmKaty 20 h after pathogen inoculation, indicating that rapid cell death is a mechanism of LmmKaty to restrict pathogen invasion. Rapid accumulations of defense related （DR） gene transcripts, phenylalanine ammonia lyase and β-glucanase, were observed beginning at 6 h and were obvious at 16 h and 24 h after inoculation in an incompatible interaction. Rapid transcript accumulations of PR-1 and chitinase had occurred by 24 h after inoculation in an incompatible interaction. Accumulations of these transcripts were delayed in the compatible interaction. These results indicate that host active defense responses occur 24 h after pathogen inoculation and that LmmKaty exhibits enhanced resistance to M. grisea. It is suggested that the autofluorescence and expression of the DR genes after heavy inoculation are important cytological and molecular markers respectively for early determination of the host response to M. grisea in the rice blast system.

iTRAQ-based quantitative proteomics analysis of defense responses triggered by the pathogen Rhizoctonia solani infection in rice

The soil-borne necrotrophic fungus Rhizoctonia solani is one of destructive fungi causing severe yield losses in various important crops. However, the host defense mechanisms against the invasion of this pathogen are poorly understood. In this study, we employed an i TRAQ-based quantitative proteomic approach to investigate host proteins responsive to R. solani using the resistant rice cultivar YSBR1. As a whole, we identified 319 differentially accumulated proteins(DAPs) after inoculation of rice plants with R. solani. Functional categorization analysis indicates that these DAPs cover a broad range of functions. Notably, a substantial portion of the DAPs are involved in cell redox homeostasis, carbohydrate metabolism, and phenylpropanoid biosynthesis, or belong to pathogenesis-related proteins, indicating that these processes/proteins play important roles in host defense against R. solani. Interestingly, all of the DAPs involved in photosynthesis and chlorophyll biosynthetic processes, and part of the DAPs involved in phenylpropanoid biosynthesis, show reduced accumulation after R. solani infection, suggesting that R. solani probably inhibits host photosynthetic system and phenylpropanoid biosynthesis to facilitate infection and colonization. In conclusion, our results provide both valuable resources and new insights into the molecular mechanisms underlying rice and R. solani interaction.

PnSCR82,a small cysteine-rich secretory protein of Phytophthora nicotianae,can enhance defense responses in plants

A number of plant pathogenic species of Phytophthora are known to produce different classes of secretory proteins during interactions with their hosts.Although several small cysteine-rich(SCR)secretory proteins,conserved in oomycete pathogens,have been identified in Phytophthora,their specific involvement in these interactions remains unknown.In this study,an SCR effector encoded by Pn SCR82 in P.nicotianae was identified and shown to have similarities to P.cactorum phytotoxic protein,Pc F(Phytophthora cactorum Fragaria).Agroinfection with potato virus X vector,Pn SCR82,was capable of inducing plant hypersensitive cell death in Nicotiana benthamiana and Solanum lycopersicum.Real-time PCR results indicated that transiently expressed Pn SCR82 in N.benthamiana leaves activated the jasmonate,salicylic acid and ethylene signaling pathways.Transient expression of Pn SCR82 enhanced plant resisitance to P.capsici.In summary,our results demonstrated that P.nicotianae Pn SCR82 elicits defensive responses in N.benthamiana and may potentially play a significant role in future crop protection programs.

Comparative transcriptome analysis reveals key genes and pathways in response to Alternaria alternata apple pathotype infection

Apple leaf spot,caused by the Alternaria alternata apple pathotype(AAAP),is an important fungal disease of apple.To understand the molecular basis of resistance and pathogenesis in apple leaf spot,the transcriptomes of two apple cultivars‘Hanfu'(HF)(resistant)and‘Golden Delicious'(GD)(susceptible)were analyzed at 0,6,18,24 and 48 h after AAAP inoculation by RNA-Seq.At each time point,a large number of significantly differentially expressed genes(DEGs)were screened between AAAP-inoculated and uninoculated apple leaves.Analysis of the common DEGs at four time points revealed significant differences in the resistance of‘HF'and‘GD'apple to AAAP infection.RLP,RNL,and JA signal-related genes were upregulated in both cultivars to restrict AAAP development.However,genes encoding CNLs,TNLs,WRKYs,and AP2s were only activated in‘HF'as part of the resistance response,of which,some play major roles in the regulation of ET and SA signal transduction.Further analysis showed that many DEGs with opposite expression trends in the two hosts may play important regulatory roles in response to AAAP infection.Transient expression of one such gene MdERF110 in‘GD'apple leaves improved AAAP resistance.Collectively,this study highlights the reasons for differential resistance to AAAP infection between‘HF'and‘GD'apples which can theoretically assist the molecular breeding of disease-resistant apple crops.

Physiological Response and Resistance of Plants to Disease and Pest Stress

This paper outlines the physiological responses of plants to pathogenic microbial infection and pest feeding stress,as well as the resistance characteristics of plants to diseases and pests,and proposes new directions for future research on crop resistance to diseases and pests.The objective of this paper is to provide a reference framework for the breeding of crops with enhanced resistance to diseases and pests,the utilization of natural immunity in crops,and the efficient prevention and control of diseases and pests.This framework is intended to facilitate the healthy and sustainable development of the agricultural industry.

Post-Translational Derepression of Invertase Activity in Source Leaves via Down-Regulation of Invertase Inhibitor Expression Is Part of the Plant Defense Response

There is increasing evidence that pathogens do not only elicit direct defense responses, but also cause pronounced changes in primary carbohydrate metabolism. Cell-wall-bound invertases belong to the key regulators of carbohydrate partitioning and source-sink relations. Whereas studies have focused so far only on the transcriptional induction of invertase genes in response to pathogen infection, the role of post-translational regulation of invertase activity has been neglected and was the focus of the present study. Expression analyses revealed that the high mRNA level of one out of three proteinaceous invertase inhibitors in source leaves of Arabidopsis thaliana is strongly repressed upon infection by a virulent strain of Pseudomonas syringae pv. tomato DC3000. This repression is paralleled by a decrease in invertase inhibitor activity. The physiological role of this regulatory mechanism is revealed by the finding that in situ invertase activity was detectable only upon infection by P. syringae. In contrast, a high invertase activity could be measured in vitro in crude and cell wall extracts prepared from both infected and non-infected leaves. The discrepancy between the in situ and in vitro invertase activity of control leaves and the high in situ invertase activity in infected leaves can be explained by the pathogen-dependent repression of invertase inhibitor expression and a concomitant reduction in invertase inhibitor activity. The functional importance of the release of invertase from post-translational inhibition for the defense response was substantiated by the application of the competitive chemical invertase inhibitor acarbose. Posttranslational inhibition of extracellular invertase activity by infiltration of acarbose in leaves was shown to increase the susceptibility to P. syringae. The impact of invertase inhibition on spatial and temporal dynamics of the repression of photosynthesis and promotion of bacterial growth during pathogen infection supports a role for extracellular invertase in plant defense. The acarbose-mediated increase in susceptibility was also detectable in sid2 and cpr6 mutants and resulted in slightly elevated levels of salicylic acid, demonstrating that the effect is independent of the salicylic acid-regulated defense pathway. These findings provide an explanation for high extractable invertase activity found in source leaves that is kept inhibited in situ by post-translational interaction between invertase and the invertase inhibitor proteins. Upon pathogen infection, the invertase activity is released by repression of invertase inhibitor expression, thus linking the local induction of sink strength to the plant defense response.

PlaD： A Transcriptomics Database for Plant Defense Responses to Pathogens, Providing New Insights into Plant Immune System

High-throughput transcriptomics technologies have been widely used to study plant transcriptional reprogramming during the process of plant defense responses, and a large quantity of gene expression data have been accumulated in public repositories. However, utilization of these data is often hampered by the lack of standard metadata annotation. In this study, we curated2444 public pathogenesis-related gene expression samples from the model plant Arabidopsis and three major crops （maize, rice, and wheat）. We organized the data into a user-friendly database termed as PlaD. Currently, PlaD contains three key features. First, it provides large-scale curated data related to plant defense responses, including gene expression and gene functional annotation data.Second, it provides the visualization of condition-specific expression profiles. Third, it allows users to search co-regulated genes under the infections of various pathogens. Using PlaD, we conducted a large-scale transcriptome analysis to explore the global landscape of gene expression in the curated data. We found that only a small fraction of genes were differentially expressed under multiple conditions, which might be explained by their tendency of having more network connections and shorter network distances in gene networks. Collectively, we hope that PlaD can serve as an important and comprehensive knowledgebase to the community of plant sciences, providing insightful clues to better understand the molecular mechanisms underlying plant immune responses. PlaD is freely available at http：//systbio.cau.edu.cn/plad/index.php or http：//zzdlab.com/plad/index.php.

Mapping of Defense Response Gene Homologs and Their Association with Resistance Loci in Maize

Defense response genes in higher plant species are involved in a variety of signal transduction pathways and biochemical reactions to counterattack invading pathogens. In this study, a total of 366 non-redundant defense response gene homologs （DRHs）, including 124 unigenes/expressed sequence tags, 226 tentative consensuses, and 16 DRH contigs have been identified by mining the Maize Genetics and Genomics and The Institute for Genomic Research maize databases using 35 essential defense response genes. Of 366 DRHs, 202 are mapped to 152 loci across ten maize chromosomes via both the genetic and in silico mapping approaches. The mapped DRHs seem to cluster together rather than be evenly distributed along the maize genome. Approximately half of these DHRs are located in regions harboring either major resistance genes or quantitative trait loci （QTL）. Therefore, this comprehensive DRH linkage map will provide reference sequences to identify either positional candidate genes for resistance genes and/or QTLs or to develop makers for fine-mapping and marker-assisted selection of resistance genes and/or QTLs.

GhWRKY33 negatively regulates jasmonate-mediated plant defense to Verticillium dahliae

Verticillium wilt,caused by Verticillium dahliae,seriously restricts the yield and quality improvement of cotton.Previous studies have revealed the involvement of WRKY members in plant defense against V.dahliae,but the underlying mechanisms involved need to be further elucidated.Here,we demonstrated that Gossypium hirsutum WRKY DNA-binding protein 33(GhWRKY33) functions as a negative regulator in plant defense against V.dahliae.GhWRKY33 expression is induced rapidly by V.dahliae and methyl jasmonate,and overexpression of GhWRKY33 reduces plant tolerance to V.dahliae in Arabidopsis.Quantitative RT-PCR analysis revealed that expression of several JA-associated genes was significantly repressed in GhWRKY33 overexpressing transgenic plants.Yeast one-hybrid analysis revealed that GhWRKY33 may repress the transcription of both AtERF1 and GhERF2 through its binding to their promoters.Protein-protein interaction analysis suggested that GhWRKY33 interacts with G.hirsutum JASMONATE ZIM-domain protein 3(GhJAZ3).Similarly,overexpression of GhJAZ3 also decreases plant tolerance to V.dahliae.Furthermore,GhJAZ3 acts synergistically with GhWRKY33 to suppress both AtERF1 and GhERF2 expression.Our results imply that GhWRKY33 may negatively regulate plant tolerance to V.dahliae via the JA-mediated signaling pathway.

Challenges and Progress in Evaluating Apple Root Resistance Responses to Pythium ultimum Infection

Due to the hidden nature of roots in the soils, it is more challenging to investigate their resistance traits and defense responses as compared to those of the aerial organs. At the same time, it is self-evident that root health is fundamental to a plant’s entire life and productivity. It is also easily conceivable that root function, physiology, morphology, and architecture are constantly impacted by the complex soil environment including both biotic and abiotic factors. This report summarizes and updates the challenges and progress in evaluating resistance responses of apple root to infection from a necrotrophic oomycete pathogen, Pythium ultimum. Several obstacles impede the progress of investigating apple root resistance traits including the difficulties of direct and real-time evaluation and the lack of a continuous supply of apple plants for repeated infection assays. Systematic and detailed analyses were made possible by implementing a micropropagation procedure for continuously generating uniform apple plants for repeated infection assays. As a result, an elite panel of apple rootstock germplasm with distinct resistance levels was identified. These apple rootstock genotypes with well-defined resistance levels are the much-needed plant materials for subsequent genomics and transgenics analyses to define the functional roles of specific candidate genes. Careful microscopic examination revealed contrasting necrosis progression patterns between resistant and susceptible genotypes, which shed light on the potential mechanisms underlying resistance traits. Our continuing research will provide a clearer view regarding the genetic elements regulating resistance traits in apple roots to P. ultimum infection.

BnaWRKY75 positively regulates the resistance against Sclerotinia sclerotiorum in ornamental Brassica napus

With the development of tourism at home and abroad,Rapeseed(Brassica napus)has become an important ornamental plant.However,its ornamental value at the inflorescence stage is greatly reduced by Sclerotinia sclerotiorum.Identification of important genes in the defense responses is critical for molecular breeding,which is an important strategy for controlling the disease.In this study,we isolated a B.napus WRKY transcription factor gene,BnaWRKY75.BnaWRKY75 was found to encode a nucleus-localized protein and exhibited relatively high expression in the stems.Arabidopsis thaliana transgenic plants expressing BnaWRKY75 showed enhanced resistance to S.sclerotiorum,and both ProBnaWRKY75:GUS and gene expression analyses showed that BnaWRKY75 was highly responsive to S.sclerotiorum infection,indicating the involvement of BnaWRKY75 in response to this infection.Furthermore,overexpression(OE)of BnaWRKY75 in B.napus significantly enhanced the resistance to S.sclerotiorum,whereas the resistance was reduced in RNAi transgenic B.napus plants.Moreover,the BnaWRKY75-OE B.napus plants exhibited constitutive activation of salicylic acid-,jasmonic acid-,and ethylene-mediated defense responses and the inhibition of both H_(2)O_(2)and O_(2)·^(-)accumulation in response to this pathogen.By contrast,BnaWRKY75-RNAi plants showed a reverse pattern,suggesting that BnaWRKY75 is involved in hormonal signaling pathways and in the control of reactive oxygen species accumulation.In conclusion,these data indicate that BnaWRKY75,a regulator of multiple defense responses,positively regulates resistance against S.sclerotiorum,which may guide the improvement of resistance in rapeseed.

Constitutive expression of pathogen-inducible OsWRKY31 enhances disease resistance and affects root growth and auxin response in transgenic rice plants

WRKY transcription factors have many regulatory roles we isolated a rice WRKY gene （OsWRKY31） that is induced in response to biotic and abiotic stresses. In this study, by the rice blast fungus Magnaporthe grisea and auxin. This gene encodes a polypeptide of 211 amino-acid residues and belongs to a subgroup of the rice WRKY gene family that probably originated after the divergence of monocot and dicot plants. OsWRKY31 was found to be localized to the nucleus of onion epidermis cells to transiently express OsWRKY31-eGFP fusion protein. Analysis of OsWRKY31 and its mutants fused with a Gal4 DNA-binding domain indicated that OsWRKY31 has transactivation activity in yeast. Overexpression of the OsWRKY31 gene was found to enhance resistance against infection with M. grisea, and the transgenic lines exhibited reduced lateral root formation and elongation compared with wild-type and RNAi plants. The lines with overexpression showed constitutive expression of many defense-related genes, such as PBZI and OsSci2, as well as early auxin-response genes, such as OslAA4 and OsCrll genes. Furthermore, the plants with overexpression were less sensitive to exogenously supplied IBA, NAA and 2,4-1） at high concentrations, suggesting that overexpression of the OsWRKY31 gene might alter the auxin response or transport. These results also suggest that OsWRKY31 might be a common component in the signal transduction pathways of the auxin response and the defense response in rice.

OsWRKY03, a rice transcriptional activator that functions in defense signaling pathway upstream of OsNPR1

WRKY family proteins are a class of plant specific transcription factors that involve in many stress response pathways. It has been shown that one Arabidopsis WRKY protein, AtWRKY29/22, is activated by MAP kinase signaling cascade and confers resistance to both bacterial and fungal pathogens. However, little is known about the biological roles of WRKY proteins in rice. In this study, we investigated the expression patterns of rice AtWRKY29/22 homolog, OsWRKY03, under different conditions, and also its possible role involved in plant defense. Our results showed that OsWRKY03 was up-regulated by several defense signaling molecules or different treatments. Further analysis revealed that the expression of OsWRKY03 was light dependent. Transcriptional activation activity of OsWRKY03 was also demonstrated by yeast functional assay. Transient expression of OsWRKY03-GFP fusion protein in onion epidermis cells showed that OsWRKY03 was a nuclear localized protein. OsNPR1 as well as several other pathogenesis-related genes, such as OsPRlb, phenylalanine ammonia-lyase （ZB8） and peroxidase （POX22.3）, were induced in OsWRKYO3-overexpressing transgenic plants. These results indicated that OsWRKY03 is located upstream of OsNPR 1 as a transcriptional activator in salicylic acid （SA）-dependent or jasmonic acid （JA）-dependent defense signaling cascades.

The Arabidopsis P450 protein CYP82C2 modulates jasmonateinduced root growth inhibition, defense gene expression and indole glucosinolate biosynthesis

Jasmonic acid （JA） is a fatty acid-derived signaling molecule that regulates a broad range of plant defense responses against herbivores and some microbial pathogens. Molecular genetic studies have established that JA also performs a critical role in several aspects of plant development. Here, we describe the characterization of the Arabidopsis mutantjasmonic acid-hypersensitivel-1 （jah1-1）, which is defective in several aspects of JA responses. Although the mutant exhibits increased sensitivity to JA in root growth inhibition, it shows decreased expression of JA-inducible defense genes and reduced resistance to the necrotrophic fungus Botrytis cinerea. Gene cloning studies indicate that these defects are caused by a mutation in the cytochrome P450 protein CYP82C2. We provide evidence showing that the compromised resistance of thejah1-1 mutant to B. cinerea is accompanied by decreased expression of JA-induced defense genes and reduced accumulation of JA-induced indole glucosinolates （IGs）. Conversely, the enhanced resistance to B. cinerea in CYP82C2-overexpressing plants is accompanied by increased expression of JA-induced defense genes and elevated levels of JA-induced IGs. We demonstrate that CYP82C2 affects JA-induced accumulation of the IG biosynthetic precursor tryptophan （Trp）, but not the JA-induced IAA or pathogen-induced camalexin. Together, our results support a hypothesis that CYP82C2 may act in the metabolism of Trp-derived secondary metabolites under conditions in which JA levels are elevated. Thejah1-1 mutant should thus be important in future studies toward understanding the mechanisms underlying the complexity of JA-mediated differential responses, which are important for plants to adapt their growth to the ever-changing environments.

Comparative proteomic profiles of resistant/susceptible cucumber leaves in response to downy mildew infection

Downy mildew is a serious disease in cucumber production worldwide,which is caused by Pseudoperonospora cubensis(Berk.&Curt.)Rostov.Underlying the mechanism of cucumber response to downy mildew infection is important for breeding improvement and production;however,the research remains largely elusive.A comparative proteomic approach was used to reveal the differential accumulation of the proteomes from leaves of cucumber(susceptible line and resistant line)that were inoculated with P.cubensis or not by two-dimensional electrophoresis and MALDI-TOF/TOF MS.A total of 76 protein spots were successfully identified with significant changes in abundance(>2-fold,P<0.05)in downy mildew infected or not leaves for the susceptible line and resistant line.By the functional annotation,these proteins were classified into 8 groups including photosynthesis(29%),energy and metabolism(29%),cell rescue and defense(17%),and protein biosynthesis,folding and degradation(13%),unclassified(7%),nucleotide metabolism(3%),signal transduction(1%)and cellular process(1%).Among the 17 differentially expressed proteins between the resistant and susceptible cucumber line,most of the protein spots were concentrated in cell rescue and defense(4)and energy and metabolism(4).Moreover,a schematic diagram containing majority of the metabolic pathways of cucumber leaves in response to downy mildew was proposed.This network revealed the positive effect of several functional components in cucumber seedlings’resistant to downy mildew such as accumulation of energy supply and resistance-related proteins,hastened protein metabolism and photorespiratory,inhibited photosynthesis,and triggered photosystem repair and programmed cell death.Taken together,these results have advanced a further understanding of the key metabolic pathways of cucumber resistance to downy mildew and pathogen control in the proteomic level.

A Non-canonical Excitatory PV RGC–PV SC Visual Pathway for Mediating the Looming-evoked Innate Defensive Response

Parvalbumin-positive retinal ganglion cells(PV+RGCs)are an essential subset of RGCs found in various species.However,their role in transmitting visual information remains unclear.Here,we characterized PV+RGCs in the retina and explored the functions of the PV+RGC-mediated visual pathway.By applying multiple viral tracing strategies,we investigated the downstream of PV+RGCs across the whole brain.Interestingly,we found that the PV+RGCs provided direct monosynaptic input to PV+excitatory neurons in the superficial layers of the superior colliculus(SC).Ablation or suppression of SC-projecting PV+RGCs abolished or severely impaired the flight response to looming visual stimuli in mice without affecting visual acuity.Furthermore,using transcriptome expression profiling of individual cells and immunofluorescence colocalization for RGCs,we found that PV+RGCs are predominant glutamatergic neurons.Thus,our findings indicate the critical role of PV+RGCs in an innate defensive response and suggest a non-canonical subcortical visual pathway from excitatory PV+RGCs to PV+SC neurons that regulates looming visual stimuli.These results provide a potential target for intervening and treating diseases related to this circuit,such as schizophrenia and autism.