RESUMO
KEY MESSAGE: Here, we report that ZmAGO18b encoding an argonaute protein is a negative regulator of maize resistance against southern leaf blight. Southern leaf blight caused by fungal pathogen Cochliobolus heterostrophus is a destructive disease on maize throughout the world. Argonaute (AGO) proteins, key regulators in small RNA pathway, play important roles in plant defense. But whether they have function in maize resistance against C. heterostrophus is unknown. Association analysis between the nucleic variation of 18 ZmAGO loci with disease phenotype against C. heterostrophus was performed, and the ZmAGO18b locus was identified to be associated with resistance against C. heterostrophus. Overexpression of ZmAGO18b gene suppresses maize resistance against C. heterostrophus, and mutation of ZmAGO18b enhances maize resistance against C. heterostrophus. Further, we identified the resistant haplotype of ZmAGO18b by association analysis of natural variation in ZmAGO18b genomic DNA sequences with seedling resistance phenotypes against C. heterostrophus and confirmed the resistant haplotype is co-segregated with resistance phenotypes against C. heterostrophus in two F2 populations. In sum, this study reports that ZmAGO18b negatively regulates maize resistance against C. heterostrophus.
Assuntos
Doenças das Plantas , Zea mays , Zea mays/genética , Zea mays/microbiologia , Mutação , Fenótipo , Doenças das Plantas/genética , Doenças das Plantas/microbiologiaRESUMO
Broad-spectrum resistance has great values for crop breeding. However, its mechanisms are largely unknown. Here, we report the cloning of a maize NLR gene, RppK, for resistance against southern corn rust (SCR) and its cognate Avr gene, AvrRppK, from Puccinia polysora (the causal pathogen of SCR). The AvrRppK gene has no sequence variation in all examined isolates. It has high expression level during infection and can suppress pattern-triggered immunity (PTI). Further, the introgression of RppK into maize inbred lines and hybrids enhances resistance against multiple isolates of P. polysora, thereby increasing yield in the presence of SCR. Together, we show that RppK is involved in resistance against multiple P. polysora isolates and it can recognize AvrRppK, which is broadly distributed and conserved in P. polysora isolates.
Assuntos
Basidiomycota , Zea mays , Basidiomycota/genética , Mapeamento Cromossômico , Clonagem Molecular , Resistência à Doença/genética , Melhoramento Vegetal , Doenças das Plantas/genética , Puccinia , Zea mays/genéticaRESUMO
Natural alleles that control multiple disease resistance (MDR) are valuable for crop breeding. However, only one MDR gene has been cloned in maize, and the molecular mechanisms of MDR remain unclear in maize. In this study, through map-based cloning we cloned a teosinte-derived allele of a resistance gene, Mexicana lesion mimic 1 (ZmMM1), which causes a lesion mimic phenotype and confers resistance to northern leaf blight (NLB), gray leaf spot (GLS), and southern corn rust (SCR) in maize. Strong MDR conferred by the teosinte allele is linked with polymorphisms in the 3' untranslated region of ZmMM1 that cause increased accumulation of ZmMM1 protein. ZmMM1 acts as a transcription repressor and negatively regulates the transcription of specific target genes, including ZmMM1-target gene 3 (ZmMT3), which functions as a negative regulator of plant immunity and associated cell death. The successful isolation of the ZmMM1 resistance gene will help not only in developing broad-spectrum and durable disease resistance but also in understanding the molecular mechanisms underlying MDR.
Assuntos
Resistência à Doença/genética , Genes de Plantas , Doenças das Plantas/imunologia , Proteínas de Plantas/genética , Proteínas Repressoras/genética , Zea mays/genética , Alelos , Clonagem Molecular , Regulação da Expressão Gênica de Plantas , Fenótipo , Doenças das Plantas/genética , Proteínas de Plantas/fisiologia , RNA de Plantas/genética , RNA de Plantas/fisiologia , RNA não Traduzido/genética , RNA não Traduzido/fisiologia , Proteínas Repressoras/fisiologiaRESUMO
A new catalytic manifold that merges photoredox with nickel catalysis in aqueous solution is presented. Specifically, the combination of a highly active, yet air-stable, nickel precatalyst with a new electron-deficient pyridyl carboxamidine ligand was key to the development of a water-compatible nickel catalysis platform, which is a crucial requirement for the preparation of DNA-encoded libraries (DELs). Together with an iridium-based photocatalyst and a powerful light source, this dual catalysis approach enabled the efficient decarboxylative arylation of α-amino acids with DNA-tagged aryl halides. This C(sp2)-C(sp3) coupling tolerates a wide variety of functional groups on both the amino acid and the aryl halide substrates. Due to the mild and DNA-compatible reaction conditions, the presented transformation holds great potential for the construction of DELs. This was further evidenced by showing that well plate-compatible LED arrays can serve as competent light sources to facilitate parallel synthesis. Lastly, we demonstrate that this procedure can serve as a blueprint toward the adaptation of other established nickel metallaphotoredox transformations to the idiosyncratic requirements of a DEL.