Abstract
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.
Highlights
To defend against pathogenic microorganisms, plants have evolved a multilayered and sophisticated immune system including pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI; McHale et al, 2006; Cui et al, 2015)
The pathogenesis-related 1 (PR1) levels were noticeably induced in mutant plants at 6 hpts in Mo17 × H95 background and at 24 hpts in the B73× H95 background, while the PR5 levels increased in mutant plants at 24 hpts and 48 hpts in B73 × H95 and Mo17 × H95, respectively (Supplementary Figure 2)
We found that the genes predicted to encode the salicylic acid (SA) receptors, nonexpressor of pathogenesis-related genes 1 (NPR1) and NPR4, and the SA marker genes, pathogenesis-related 1 (PR1) and PR5 were significantly differentially expressed in Rp1-D21 mt
Summary
To defend against pathogenic microorganisms, plants have evolved a multilayered and sophisticated immune system including pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI; McHale et al, 2006; Cui et al, 2015). Regulatory Network and ZmUGTs in Defense Response localized at the surface of plant cells, while ETI is triggered when the intracellular receptors termed nucleotide-binding leucine-rich-repeat (NLR) proteins recognize the specific effector proteins secreted from pathogens. PRR- and NLR-mediated downstream signaling pathways result in some similar immune outputs, such as increased expression of pathogenesis-related (PR) genes and the burst of reactive oxygen species (ROS). The activation of SA biosynthesis, metabolism, and signaling pathways play critical roles for both PTI- and ETI-mediated defense responses (Vlot et al, 2009; Ding et al, 2018). The Arabidopsis uridine diphosphate (UDP)dependent glycosyltransferase UGT76D1, which catalyzes the formation of DHBA glycosides, leads to the induction of HR, a burst of ROS, the increased expression of PR genes and enhanced resistance to Pst DC3000 (Huang et al, 2018). Four DHBA glucosyltransferase homologs of ZmUGTs, were highly induced, two of which we show may have important roles in modulating Rp1D21-mediated HR
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call