Role for novel family of pathogen-induced cysteine-rich transmembrane proteins in disease resistance

Plants possess a sophisticated immune system to protect themselves against pathogen attack. The defense hormone salicylic acid (SA) is an important player in the plant immune gene regulatory network. Using RNA-seq time series data of leaves treated with SA, we identified a largely uncharacterized SA-responsive gene family of eight members that are all activated in response to various pathogens or their immune elicitors and encode small proteins with cysteine-rich transmembrane domains. Based on their nucleotide similarity and chromosomal position, the designated athogen-induced ysteine-rich transembrane protein (PCM) genes were subdivided into three subgroups consisting of (subgroup I), (subgroup II), and 8 (subgroup III). Of the genes, only (also known as ) has previously been implicated in plant immunity. Transient expression assays in indicated that most PCM proteins localize to the plasma membrane. Ectopic overexpression of the in Arabidopsis resulted in all eight cases in enhanced resistance against the biotrophic oomycete pathogen Noco2. Additionally, overexpression of subgroup I genes conferred enhanced resistance to the hemi-biotrophic bacterial pathogen pv. DC3000. Ectopic overexpression of the also affected the expression of genes related to light signaling and development, and accordingly PCM-overexpressing seedlings displayed elongated hypocotyl growth. These results point to a function of PCMs in both disease resistance and photomorphogenesis, connecting both biological processes, possibly via effects on membrane structure or activity of interacting proteins at the plasma membrane.