Alternative functions of Arabidopsis Yellow Stripe-Like3: from metal translocation to pathogen defense

Yellow stripe-like1 (YSL1) and YSL3 are involved in iron (Fe) and copper (Cu) translocation. Previously, we reported that upregulation of YSL1 and YSL3 under excess Cu caused high accumulation of Cu in the siz1 mutant, impaired in small ubiquitin-like modifier (SUMO) E3 ligase. Interestingly, the siz1 mutant contains high levels of salicylic acid (SA), involved in plant defense against biotrophic pathogens. In this study, we found that YSL1 and YSL3 were upregulated by SA. SA-regulated YSL3 but not YSL1 depended on nonexpressor of PR1 (NPR1). Susceptibility to the pathogen Pseudomonas syringe pv. tomato (Pst) DC3000 was greater for ysl3 than the wild type. Also, during Pst DC3000 infection, YSL3 was positively regulated by SA signaling through NPR1 and the upregulation was enhanced in the coi1 mutant that defective in the jasmonic acid (JA) receptor, coronatine insensitive1. This line of evidence indicates that the regulation of YSL3 is downstream of SA signaling and interplays with JA signaling for involvement in pathogen-induced defense. We provide new insights into the biological function of the metal transporter YSL3 in plant pathogen defense.