Table_3_Multi-Omics Analyses Reveal the Regulatory Network and the Function of ZmUGTs in Maize Defense Response.XLSX

Maize is one of the major crops in the world; however, diseases caused by various pathogens seriously affect its yield and quality. The maize Rp1-D21 mutant (mt) caused by the intragenic recombination between two nucleotide-binding, leucine-rich repeat (NLR) proteins, exhibits autoactive hypersensitive response (HR). In this study, we integrated transcriptomic and metabolomic analyses to identify differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) in Rp1-D21 mt compared to the wild type (WT). Genes involved in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) were enriched among the DEGs. The salicylic acid (SA) pathway and the phenylpropanoid biosynthesis pathway were induced at both the transcriptional and metabolic levels. The DAMs identified included lipids, flavones, and phenolic acids, including 2,5-DHBA O-hexoside, the production of which is catalyzed by uridinediphosphate (UDP)-dependent glycosyltransferase (UGT). Four maize UGTs (ZmUGTs) homologous genes were among the DEGs. Functional analysis by transient co-expression in Nicotiana benthamiana showed that ZmUGT9250 and ZmUGT5174, but not ZmUGT9256 and ZmUGT8707, partially suppressed the HR triggered by Rp1-D21 or its N-terminal coiled-coil signaling domain (CCD21). None of the four ZmUGTs interacted physically with CCD21 in yeast two-hybrid or co-immunoprecipitation assays. We discuss the possibility that ZmUGTs might be involved in defense response by regulating SA homeostasis.

玉米是全球主要农作物之一，然而各类病原物引发的病害严重制约其产量与品质。玉米Rp1-D21突变体（maize Rp1-D21 mutant, mt）由两个核苷酸结合富亮氨酸重复（nucleotide-binding, leucine-rich repeat, NLR）蛋白发生基因内重组产生，表现出自激活超敏反应（hypersensitive response, HR）。本研究整合转录组与代谢组分析方法，在Rp1-D21突变体与野生型（wild type, WT）中鉴定出差异表达基因（differentially expressed genes, DEGs）与差异积累代谢物（differentially accumulated metabolites, DAMs）。差异表达基因中富集了参与病原相关分子模式触发免疫（pathogen-associated molecular pattern-triggered immunity, PTI）与效应因子触发免疫（effector-triggered immunity, ETI）的功能基因。水杨酸（salicylic acid, SA）通路与苯丙烷生物合成通路在转录与代谢两个层面均被诱导激活。本次鉴定得到的差异积累代谢物涵盖脂类、黄酮类与酚酸类物质，其中2,5-DHBA O-己糖苷的合成由尿苷二磷酸（UDP）依赖型糖基转移酶（uridinediphosphate, UDP-dependent glycosyltransferase, UGT）催化。四个玉米UGT同源基因均属于本次鉴定出的差异表达基因范畴。通过本氏烟草（Nicotiana benthamiana）瞬时共表达开展的功能分析显示，ZmUGT9250与ZmUGT5174可部分抑制Rp1-D21或其N端卷曲螺旋信号结构域（coiled-coil signaling domain, CCD21）触发的超敏反应，而ZmUGT9256与ZmUGT8707无此功能。酵母双杂交（yeast two-hybrid）与免疫共沉淀（co-immunoprecipitation）实验结果均表明，这四个ZmUGT均未与CCD21发生物理互作。本研究讨论了ZmUGT可能通过调控水杨酸稳态参与植物防御反应的可能性。