Project description:BACKGROUND:White rot is one of the most dangerous fungal diseases and can considerably affect grape berry production and quality. However, few studies have focused on this disease, and thus, finding candidate white rot resistance genes is of great importance for breeding resistant grapevine cultivars. Based on field observations and indoor experiments, the cultivars "Victoria" and "Zhuosexiang" showed significant differences in white rot resistance. For understanding the molecular mechanisms behind it, different phenotypes of grapevine leaves were used for RNA sequencing via Illumina and single-molecule real-time (SMRT) sequencing technology. RESULTS:A transcript library containing 53,906 reads, including known and novel transcripts, was constructed following the full-length transcriptome sequencing of the two grapevine cultivars. Genes involved in salicylic acid (SA) and jasmonic acid (JA) synthesis pathways showed different expression levels. Furthermore, four key transcription factors (TFs), NPR1, TGA4, Pti6, and MYC2, all involved in the SA and JA signal pathways were identified, and the expression profile revealed the different regulation of the pathogenesis related protein1 (PR1) resistance gene, as mediated by the four TFs. CONCLUSIONS:Full-length transcript sequencing can substantially improve the accuracy and integrity of gene prediction and gene function research in grapevine. Our results contribute to identify candidate resistance genes and improve our understanding of the genes and regulatory mechanisms involved in grapevine resistance to white rot.
Project description:BackgroundThe WRKY transcription factors play significant roles in plant growth, development, and defense responses. However, in cotton, the molecular mechanism of most WRKY proteins and their involvement in Verticillium wilt tolerance are not well understood.ResultsGhWRKY70 is greatly up-regulated in cotton by Verticillium dahliae. Subcellular localization suggests that GhWRKY70 is only located in the nucleus. Transcriptional activation of GhWRKY70 further demonstrates that GhWRKY70 function as a transcriptional activator. Transgenic Arabidopsis plants overexpressing GhWRKY70 exhibited better growth performance and higher lignin content, antioxidant enzyme activities and jasmonic acid (JA) levels than wild-type plants after infection with V. dahliae. In addition, the transgenic Arabidopsis resulted in an enhanced expression level of AtAOS1, a gene related to JA synthesis, further leading to a higher JA accumulation compared to the wild type. However, the disease index (DI) values of the VIGS-treated cotton plants with TRV:WRKY70 were also significantly higher than those of the VIGS-treated cotton plants with TRV:00. The chlorophyll and lignin contents of TRV:WRKY70 plants were significantly lower than those of TRV:00 plants. GhAOS1 expression and JA abundance in TRV:WRKY70 plants were decreased. The GhWRKY70 protein was confirmed to bind to the W-box element in the promoter region of GhAOS by yeast one-hybrid assay and transient expression.ConclusionThese results indicate that the GhWRKY70 transcription factor is a positive regulator in Verticillium wilt tolerance of cotton, and may promote the production of JA via regulation of GhAOS1 expression.
Project description:Land plants protect themselves from ultraviolet-B (UV-B) by accumulating UV-absorbing metabolites, which may also function as anti-insect toxins. Previous studies have shown that UV-B enhances the resistance of different plant species to pierce-sucking pests; however, whether and how UV-B influences plant defense against chewing caterpillars are not well understood. Here we show that UV-B treatment increased Spodoptera litura herbivory-induced jasmonic acid (JA) production in Arabidopsis and thereby Arabidopsis exhibited elevated resistance to S. litura. Using mutants impaired in the biosynthesis of JA and the defensive metabolites glucosinolates (GSs), we show that the UV-B-induced resistance to S. litura is dependent on the JA-regulated GSs and an unidentified anti-insect metabolite(s). Similarly, UV-B treatment also enhanced the levels of JA-isoleucine conjugate and defense-related secondary metabolites in tobacco, rice, and maize after these plants were treated with simulated herbivory of lepidopteran insects; consistently, these plants showed elevated resistance to insect larvae. Using transgenic plants impaired in JA biosynthesis or signaling, we further demonstrate that the UV-B-enhanced defense responses also require the JA pathway in tobacco and rice. Our findings reveal a likely conserved JA-dependent mechanism by which UV-B enhances plant defense against lepidopteran insects.
Project description:Plants have evolved a sophisticated defense system that employs various hormone pathways to defend against attacks by insect pests. Cytokinin (CK) plays an important role in plant growth and stress tolerance, but the role of CKs in plant-insect interaction remains largely unclear. Here, we report that CKs act as a positive regulator in rice resistance against brown planthopper (BPH), a devastating insect pest of rice. We found that BPH feeding promotes CK biosynthesis and signaling in rice. Exogenous application of CKs significantly increased the rice resistance to BPH. Increasing endogenous CKs by knocking out cytokinin oxidase/dehydrogenase (OsCKXs) led to enhanced resistance to BPH. Moreover, the levels of the plant hormone jasmonic acid (JA) and the expression of JA-responsive genes were elevated by CK treatment and in OsCKXs knockout plants. Furthermore, JA-deficient mutant og1 was more susceptible to BPH, and CK-induced BPH resistance was suppressed in og1. These results indicate that CK-mediated BPH resistance is JA-dependent. Our findings provide the direct evidence for the novel role of CK in promoting insect resistance, and demonstrate that CK-induced insect resistance is JA-dependent. These results provide important guidance for effective pest management strategies in the future.
Project description:Grape white rot, a devastating disease of grapevines caused by Coniella diplodiella (Speg.) Sacc., leads to significant yield losses in grape. Breeding grape cultivars resistant to white rot is essential to reduce the regular use of chemical treatments. In recent years, Chinese grape species have gained more attention for grape breeding due to their high tolerance to various biotic and abiotic factors along with changing climatic conditions. In this study, we employed whole-genome resequencing (WGR) to genotype the parents of 'Manicure Finger' (Vitis vinifera, female) and '0940' (Vitis davidii, male), along with 101 F1 mapping population individuals, thereby constructing a linkage genetic map. The linkage map contained 9337 single-nucleotide polymorphism (SNP) markers with an average marker distance of 0.3 cM. After 3 years of phenotypic evaluation of the progeny for white rot resistance, we confirmed one stable quantitative trait locus (QTL) for white rot resistance on chromosome 3, explaining up to 17.9% of the phenotypic variation. For this locus, we used RNA-seq to detect candidate gene expression and identified PR1 as a candidate gene involved in white rot resistance. Finally, we demonstrated that recombinant PR1 protein could inhibit the growth of C. diplodiella and that overexpression of PR1 in susceptible V. vinifera increased grape resistance to the pathogen.
Project description:WRKY genes are transcription factors involved in plant response to pathogen attacks in many plant species. These proteins have been shown to activate expression of defence genes in a salicylic acid- and/or jasmonic acid-dependent signalling pathway. To understand the molecular mechanisms involved in grapevine defence, we previously identified a WRKY gene, VvWRKY1, which was able to enhance tolerance to fungal pathogens when overexpressed in tobacco. To elucidate its role in grapevine, we generated transgenic grapevines that overexpress VvWRKY1. Microarray analyses were performed to compare global gene expression in leaves of the transgenic and wild-type lines. Results showed that expression of genes encoding defence-related proteins was enhanced in the transgenic 35S::VvWRKY1 line. Quantitative RT-PCR analysis confirmed that three genes putatively involved in jasmonic acid signalling pathway, two genes encoding JASMONATE ZIM-domain (JAZ) proteins and one lipoxygenase, are over-expressed. The ability of VvWRKY1 to trans-activate their corresponding promoters was confirmed by transient expression assay in grape protoplasts. After challenging with the downy mildew pathogen Plasmopara viticola, resistance was enhanced in the transgenic line compared to the wild-type line. These results suggest that VvWRKY1 transcription factor is able to control plant disease resistance to one of the main grapevine pathogen by activating jasmonic acid signalling pathway in grapevine.
Project description:Verticillium dahliae, one of the most destructive fungal pathogens of several crops, challenges the sustainability of cotton productivity worldwide because very few widely-cultivated Upland cotton varieties are resistant to Verticillium wilt (VW). Here, we report that REVEILLE2 (RVE2), the Myb-like transcription factor, confers the novel function in resistance to VW by regulating the jasmonic acid (JA) pathway in cotton. RVE2 expression was essentially required for the activation of JA-mediated disease-resistance response. RVE2 physically interacted with TPL/TPRs and disturbed JAZ proteins to recruit TPL and TPR1 in NINJA-dependent manner, which regulated JA response by relieving inhibited-MYC2 activity. The MYC2 then bound to RVE2 promoter for the activation of its transcription, forming feedback loop. Interestingly, a unique truncated RVE2 widely existing in D-subgenome (GhRVE2D) of natural Upland cotton represses the ability of the MYC2 to activate GhRVE2A promoter but not GausRVE2 or GbRVE2. The result could partially explain why Gossypium barbadense popularly shows higher resistance than Gossypium hirsutum. Furthermore, disturbing the JA-signalling pathway resulted into the loss of RVE2-mediated disease-resistance in various plants (Arabidopsis, tobacco and cotton). RVE2 overexpression significantly enhanced the resistance to VW. Collectively, we conclude that RVE2, a new regulatory factor, plays a pivotal role in fine-tuning JA-signalling, which would improve our understanding the mechanisms underlying the resistance to VW.
Project description:The cytochrome P450 monooxygenases (P450s) represent a large and important enzyme superfamily in plants. They catalyze numerous monooxygenation/hydroxylation reactions in biochemical pathways, P450s are involved in a variety of metabolic pathways and participate in the homeostasis of phytohormones. The CYP82 family genes specifically reside in dicots and are usually induced by distinct environmental stresses. However, their functions are largely unknown, especially in soybean (Glycine max L.). Here, we report the function of GmCYP82A3, a gene from soybean CYP82 family. Its expression was induced by Phytophthora sojae infection, salinity and drought stresses, and treatment with methyl jasmonate (MeJA) or ethephon (ETH). Its expression levels were consistently high in resistant cultivars. Transgenic Nicotiana benthamiana plants overexpressing GmCYP82A3 exhibited strong resistance to Botrytis cinerea and Phytophthora parasitica, and enhanced tolerance to salinity and drought stresses. Furthermore, transgenic plants were less sensitive to jasmonic acid (JA), and the enhanced resistance was accompanied with increased expression of the JA/ET signaling pathway-related genes.
Project description:Rice stripe virus (RSV) is one of the most destructive viral diseases affecting rice production. However, so far, only one RSV resistance gene has been cloned, the molecular mechanisms underlying host-RSV interaction are still poorly understood. Here, we show that increasing levels or signaling of brassinosteroids (BR) and jasmonic acid (JA) can significantly enhance the resistance against RSV. On the contrary, plants impaired in BR or JA signaling are more susceptible to RSV. Moreover, the enhancement of RSV resistance conferred by BR is impaired in OsMYC2 (a key positive regulator of JA response) knockout plants, suggesting that BR-mediated RSV resistance requires active JA pathway. In addition, we found that RSV infection suppresses the endogenous BR levels to increase the accumulation of OsGSK2, a key negative regulator of BR signaling. OsGSK2 physically interacts with OsMYC2, resulting in the degradation of OsMYC2 by phosphorylation and reduces JA-mediated defense to facilitate virus infection. These findings not only reveal a novel molecular mechanism mediating the crosstalk between BR and JA in response to virus infection and deepen our understanding about the interaction of virus and plants, but also suggest new effective means of breeding RSV resistant crops using genetic engineering.
Project description:Patatin-like proteins (PLPs) have non-specific lipid acyl hydrolysis (LAH) activity, which can hydrolyze membrane lipids into fatty acids and lysophospholipids. The vital role of PLPs in plant growth and abiotic stress has been well documented. However, the function of PLPs in plant defense responses against pathogens is still poorly understood. Here, we isolated and identified a novel cotton (Gossypium hirsutum) PLP gene GhPLP2. The expression of GhPLP2 was induced upon treatment with Verticillium dahliae, the signaling molecules jasmonic acid (JA) and ethylene (ETH) in cotton plants. Subcellular localization revealed that GhPLP2 was localized to the plasma membrane. GhPLP2-silenced cotton plants were more susceptible to infection by V. dahliae, while the overexpression of GhPLP2 in Arabidopsis enhanced its resistance to V. dahliae, which was apparent as mild symptoms, and a decrease in the disease index and fungal biomass. The hypersensitive response, deposition of callose, and H2O2 accumulation triggered by V. dahliae elicitor were reduced in GhPLP2-silenced cotton plants. The overexpression of GhPLP2 in Arabidopsis resulted in the accumulation of linoleic acid (LA, 18:2) and α-linolenic acid (ALA, 18:3) and facilitated the biosynthesis of JA and JA-mediated defensive responses. GhPLP2 silencing in cotton plants consistently reduced the accumulation of linoleic acid (LA, 18:2) and α-linolenic acid (ALA, 18:3) and suppressed the biosynthesis of JA and the defensive responses mediated by JA. These results indicate that GhPLP2 is involved in the resistance of cotton to V. dahliae by maintaining fatty acid metabolism pools for JA biosynthesis and activating the JA signaling pathway.