Project description:Some pathogen-derived effectors reprogram mRNA splicing in their host plant to regulate plant immune responses. The fungus Exserohilum turcicum is the causal agent of northern corn leaf blight, a damaging maize (Zea mays) disease. However, the low efficiency of genetic transformation of E. turcicum has hampered research on its effectors and whether E. turcicum effectors interfere with RNA splicing remained unknown. Here, using an alternative splicing (AS) reporter system, we identified the secreted protein EtEC81 (Exserohilum turcicum effector 81), which modulates the AS of maize pre-mRNAs and negatively regulates the pathogenicity of E. turcicum. EtEC81 physically interacts with EtEC81-interactiNG protein 1 (ZmEIP1), which associates with maize spliceosome components, regulating AS and positively regulating the defense response against E. turcicum. EtEC81 binding further enhanced the effect of ZmEIP1 on AS. Transcriptome analysis revealed 119 common genes with altered AS in maize plants transiently overexpressing ZmEIP1 or EtEC81, suggesting that these factors cause the mis-regulation of cellular activities and thus induce immune responses. We used RT-qPCR to verify representative AS events in the plants transiently overexpressing ZmEIP1 and EtEC81. Together, our results suggest that the EtEC81 effector targets ZmEIP1 to reprogram pre-mRNA splicing in maize.
Project description:The fungus Exserohilum turcicum is the causal agent of northern corn leaf blight, a damaging maize (Zea mays) disease worldwide. Here, using an alternative splicing (AS) reporter system, we identified the secreted protein EtEC81 (Exserohilum turcicum effector 81), which modulates the AS of maize pre-mRNAs and negatively regulates the pathogenicity of E. turcicum. EtEC81 physically interacts with EtEC81-interactiNG protein 1 (ZmEIP1), which associates with maize spliceosome components, regulating AS and positively regulating the defense response against E. turcicum. EtEC81 binding further enhanced the effect of ZmEIP1 on AS.
Project description:Wall associated kinases (WAKs) have recently been identified as major components of fungal and bacterial disease resistance in several cereal crop species. However, the molecular mechanisms of WAK-mediated resistance remain largely unknown. Here, we applied the RNAseq approach to investigate the function of the maize gene ZmWAK-RLK1 (Htn1) that confers quantitative resistance to northern corn leaf blight (NCLB) caused by the hemibiotrophic fungal pathogen Exserohilum turcicum. A transcriptome analysis of near-isogenic lines (NILs) differing for ZmWAK-RLK1 revealed that several genes involved in the biosynthesis of the secondary metabolites benzoxazinoids (BXDs) were differentially expressed in the presence of ZmWAK-RLK1.
Project description:Northern corn leaf blight (NLB), caused by the fungal pathogen Exserohilum turcicum, results significant yield reductions in infected corn. The first major locus conferring resistance to E. turcicum race 0, Ht1, was identified over 50 years ago, but despite widespread deployment the underlying gene has remained unknown. We employed map-based cloning to identify the Ht1 causal gene, which was found to be a coiled-coil nucleotide-binding, leucine-rich repeat (NLR) gene, termed PH4GP-Ht1. Transgenic testing confirmed that addition of the native PH4GP-Ht1 sequence to the susceptible maize variety PH184C resulted in resistance to E. turcicum race 0. A survey of the maize NAM genomes revealed that susceptible Ht1 alleles had very low to no expression, but overexpression of the susceptible B73 allele did not result in resistant plants, indicating that relatively minor protein sequence variations may underlie the resistance phenotype. Modeling of the PH4GP-Ht1 protein indicated that it has structural homology to the Arabidopsis NLR resistance gene ZAR1, and likely forms a similar homo-pentamer structure following activation. RNA-seq data from an infection time course revealed that one week after inoculation there was a threefold reduction in fungal biomass and a dramatic increase in DEGs when comparing mock to inoculated PH4GP-Ht1 transgenic plants and null plants. These results demonstrate that the NLR PH4GP-Ht1 is the causal gene underlying the NLB resistance phenotype of Ht1.
2022-10-03 | GSE206951 | GEO
Project description:Genomic Sequence Resource of Bipolaris maydis, Causal Agent of Southern Corn Leaf Blight of Corn Plants
Project description:BACKGROUND:Exserohilum turcicum is an important pathogen of both sorghum and maize, causing sorghum leaf blight and northern corn leaf blight. Because the same pathogen can infect and cause major losses for two of the most important grain crops, it is an ideal pathosystem to study plant-pathogen evolution and investigate shared resistance mechanisms between the two plant species. To identify sorghum genes involved in the E. turcicum response, we conducted a genome-wide association study (GWAS). RESULTS:Using the sorghum conversion panel evaluated across three environments, we identified a total of 216 significant markers. Based on physical linkage with the significant markers, we detected a total of 113 unique candidate genes, some with known roles in plant defense. Also, we compared maize genes known to play a role in resistance to E. turcicum with the association mapping results and found evidence of genes conferring resistance in both crops, providing evidence of shared resistance between maize and sorghum. CONCLUSIONS:Using a genetics approach, we identified shared genetic regions conferring resistance to E. turcicum in both maize and sorghum. We identified several promising candidate genes for resistance to leaf blight in sorghum, including genes related to R-gene mediated resistance. We present significant advancements in the understanding of host resistance to E. turcicum, which is crucial to reduce losses due to this important pathogen.
Project description:Exserohilum turcicum (sexual stage Setosphaeria turcica) is the hemibiotrophic causal agent of northern leaf blight of maize and sorghum. This study aimed to identify the genes involved in host colonization during the biotrophic and necrotrophic phases of infection. It also aimed to identify race-specific differences in gene expression. RNAseq of maize seedlings inoculated with a race 13N or 23N E. turcicum isolate was conducted before inoculation and at 2, 5, 7, and 13 days post-inoculation (dpi). Biological replicates were pooled per time point for each race and sequenced. A bioinformatics pipeline was used to identify candidate effectors, and expression was validated for selected candidates. Fungal biomass was positively correlated with the percentages of E. turcicum reads mapped, which were low at early time points (2-7 dpi) with a significant increase at 13 dpi, indicating a lifestyle switch from biotrophy to necrotrophy between 7 and 13 dpi. AVRHt1 is the putative E. turcicum effector recognized by the maize resistance gene Ht1. Consistent with this, AVRHt1 was expressed in planta by race 23N, but transcripts were absent in race 13N. In addition, specific transposable elements were expressed in 23N only. Genes encoding the virulence-associated peptidases leupeptin-inhibiting protein 1 and fungalysin were expressed in planta. Transcriptional profiles of genes involved in secondary metabolite synthesis or cell wall degradation revealed the importance of these genes during late stages of infection (13 dpi). A total of 346 expressed candidate effectors were identified, including Ecp6 and proteins similar to the secreted in xylem (SIX) effectors common to formae speciales of Fusarium oxysporum, SIX13 and SIX5. Expression profiling of Ecp6 and SIX13-like indicated a peak in expression at 5 and 7 dpi compared to 2 and 13 dpi. Sequencing of SIX13-like from diverse isolates of E. turcicum revealed host-specific polymorphisms that were mostly non-synonymous, resulting in two groups of SIX13-like proteins that corresponded to the maize or sorghum origin of each isolate. This study suggests putative mechanisms whereby E. turcicum causes disease. Identification of the candidate effector SIX13-like is consistent with the infection mode of E. turcicum through the xylem of susceptible hosts.
Project description:The basidiomycete Ustilago maydis is the causal agent of corn smut disease and induces tumor formation during biotrophic growth in its host plant maize. The Usilago maydis genome harbors a homolog to the GATA transcription factors Nit2 and AreA that act as global regulators of nitrogen catabolite repression in filamentous model fungi Neurospora crassa and Aspergillus nidulans, respectively. We aimed at resolving the role of the Ustilago maydis Nit2 homolog for the utilization of complex nitrogen sources and pathogenicity.
Project description:Ascochyta blight causes severe losses in field pea production and the search for resistance traits towards the causal agent Didymella pinodes is of particular importance to farmers. Various microsymbionts are reported to shape the plants´ immune response. However, regardless their contribution to resistance, they are hardly included in experimental designs. In this project, the bi-directional effect of the symbionts´ (rhizobia, mycorrhiza) and the leaf proteome/metabolome of two field pea cultivars with varying resistance levels towards D. pinodes is delineated.