The Northern Corn Leaf Blight Resistance Gene, Ht1, Encodes an NLR Immune Receptor
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ABSTRACT: 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.
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: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 events 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: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:Exserohilum turcicum is a fungal pathogen that causes northern corn leaf blight and sorghum leaf blight. However, strains are host-specific, meaning a strain typically only causes disease on either maize or sorghum. This pathosystem provides a unique opportunity to identify the mechanisms underlying host specificity through genomic and transcriptomic studies. To characterize host specificity, we (i) constructed de novo annotated assemblies of one sorghum- (15St008) and one maize-specific (Et52B) E. turcicum strain, ii) identified and characterized structural changes between the two genomes, and (iii) compared differential gene expression. This GEO project contains the gene expression of the maize-specific strain (Et52B) during in planta infection of maize and in axenic cultures.
Project description:Southern corn rust (SCR) is one of destructive diseases in maize caused by Puccinia polysora Undrew. (P. polysara), widely occurring in warm-temperate and tropical regions globally. To identify candidate SCR resistance-related proteins and understand the molecular mechanism underlaying the maize and P. polysara interaction, comparative proteomic analysis of susceptible and resistance maize lines was performed. A total of 6,612 proteins were successfully identified using an iTRAQ-based proteomic approach. Fold changes and statistical analysis demonstrated that 687 proteins increased and 802 proteins decreased in the resistant line, while 571 increased and 464 decreased in the susceptible line. One remorin protein, namely ZmREM1.3 (B4G1B0), was significantly induced by SCR in the resistant genotype, while decreased in susceptible genotype after P. polysara infection. Plant-specific remorin proteins have been shown to play important roles during microbial infection and plant signaling processes. Transgenic analysis showed that overexpression of ZmREM1.3 in maize confers enhanced resistance to the biotrophic fungal pathogen SCR. Upon pathogen challenge, the ZmREM1.3-overexpressing plants accumulated higher levels of defense hormones, SA and JA. Moreover, stronger induction of defense gene expression was also observed in ZmREM1.3-overexpressing maize plants in response to SCR infection. Taken together, our results support that ZmREM1.3 plays a positive role in regulating the maize defense against SCR likely through SA/JA-mediated defense signaling pathways. This is the first attempt for large scale analysis of the molecular mechanisms underlaying the maize and P. polysara interaction at the proteomic level, and the first evidence for remorin protein family in resistant to fungal disease.
Project description:Exserohilum turcicum is a fungal pathogen that causes northern corn leaf blight and sorghum leaf blight. However, strains are host-specific, meaning a strain typically only causes disease on either maize or sorghum. This pathosystem provides a unique opportunity to identify the mechanisms underlying host specificity through genomic and transcriptomic studies. To characterize host specificity, we (i) constructed de novo annotated assemblies of one sorghum- (15St008) and one maize-specific (Et52B) E. turcicum strain, ii) identified and characterized structural changes between the two genomes, and (iii) compared differential gene expression. This GEO project contains the gene expression of the sorghum-specific strain (15St008) during in planta infection of sorghum and in axenic cultures.
Project description:The biotrophic fungal pathogen Ustilago maydis cause common smut in maize, and lead to gall formation on all aerial organs, especially on maize kernel thus reduce yield. The interaction of U. maydis with maize is a well-established model to study the interaction between maize and biotrophic pathogen. U. maydis infection could activate host immune responses including: ROS accumulation, protease activation, salicylic acid signaling. U. maydis employ several strategies to overcome maize immune response, thus initial the biotrophic interaction with host. It has been suggested that genetic factors of maize host affected the disease severity of U. maydis infection, here we investigated the transcriptome profile of resistance and susceptible maize lines upon U. maydis infection, thus propose candidate maize genes involved in the defense response in maize to corn smut cause by U. maydis.
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:Diversification of effector function, driven by a co-evolutionary arms race, enables pathogens to establish compatible interactions with hosts. Structurally conserved plant pathogenesis-related PR-1 and PR-1-like (PR-1L) proteins are involved in plant defense and fungal virulence, respectively. It is unclear how fungal PR-1L counters plant defense. Here, we show that Ustilago maydis UmPR-1La and yeast ScPRY1, with conserved phenolic resistance functions, are Ser/Thr-rich region-mediated cell-surface localization proteins. However, UmPR-1La has gained specialized activity in sensing phenolics and eliciting hyphal-like formation to guide fungal growth in plants. Additionally, U. maydis hijacks maize cathepsin B-like 3 (CatB3) to release functional CAPE-like peptides by cleaving UmPR-1La’s conserved CNYD motif, subverting plant CAPE-primed immunity and promoting fungal virulence. Surprisingly, CatB3 avoids cleavage of plant PR-1s, despite the presence of the same conserved CNYD motif. Our work highlights that UmPR-1La has acquired additional dual roles to suppress plant defense and sustain the infection process of fungal pathogens.