SAR-like resistance in barley and wheat

In order to investigate SAR-like processes in a monocotyledonous crop, we characterized a new pathosystem inducing systemic immunity in barley with P. syringae pathovar japonica (Psj) or Xanthomonas translucens pathovar cerealis (Xtc). Primary infections of the first true leaf of four-week-old barley plants with Psj or Xtc enhanced resistance in systemic uninfected leaves against a subsequent Xtc challenge infection (Dey et al., 2014, Plant Physiology 166: 2133). In contrast to Arabidopsis SAR, barley systemic immunity was not dependent on HvNPR1 or accompanied by locally or systemically enhanced SA accumulation. Also, systemic immunity in barley to Xtc could be induced by local applications of the JA methyl ester (MeJA) or ABA but not by local applications of SA or its functional analog BTH. Hence, bacteria-induced systemic immunity in barley does not appear to be a canonical SAR response. Rather, RNAseq and subsequent qRT-PCR analyses associated barley systemic immunity with the enhanced transcript accumulation in the local infected and systemic uninfected tissues of at least four putative transcription factors (TFs), including 2 WRKY and 2 ETHYLENE RESPONSE FACTORs (ERFs) possibly priming the systemic uninfected tissue for gene expression changes upon secondary challenge infection to promote immunity. Ongoing work is geared towards elucidating the roles of the different TFs during systemic immunity in barley. Additionally, we aim to expand our repertoire of SAR model systems to include wheat.