RNA-Seq identification of candidate defense genes by analyzing Mythimna separata feeding-damage induced systemic resistance in balsas teosinte.

Abstract

Armyworm (Mythimna separata) is a destructive herbivore for maize. Balsas teosinte (Zea mays ssp. parviglumis), the direct wild ancestor of cultivated maize, has shown great potential to defend against herbivory. Here, based on armyworm bioassay, we compared responses of teosinte and B73 maize inbred during armyworm attack in their transcriptome profiles to elucidate the gene expression changes involved in teosinte responses to armyworm attack. The goal of this study was to identify novel resistance alleles that could serve as valuable resources for modern maize breeding. Our bioassay revealed that armyworm larvae grew less on teosinte than on maize. A follow-up transcriptomic comparison showed more down-regulated genes in maize B73 and similar numbers of up-regulated genes in both genotypes under armyworm attack. The up-regulated genes in teosinte were markedly enriched in MAPK cascade-mediated signaling pathway and phytohormone pathway. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that phytohormones jasmonic acid, ethylene, salicylic acid and abscisic acid (ABA) were actively involved in armyworm resistance of teosinte plants, and so were transcription factors such as MYBs, WRKYs and TIFYs. Interestingly, teosinte also showed high regulation in three ABA receptor PYLs. Based on differential expression analysis, we identified 30 candidate defense-related genes in teosinte, which belong to 11 gene families and the majority of the genes were up-regulated, while some of them were nonresponsive in maize. This study demonstrates that teosinte showed more vigorous defense response than maize toward armyworm attack and might be a beneficial genetic resource to improve pest resistance in cultivated maize. © 2019 Society of Chemical Industry.