New function of Hypoxia-responsive unknown protein in enhanced resistance to biotic stress.

Submergence and waterlogging lead to significant reductions in crop productivity and trigger dramatic changes in gene expression of plant biotic/abiotic stress response. Several of the host factors are involved in low-oxygen stress that is induced by endogenous reactive oxygen species (ROS) accumulation. Hypoxia-response unknown protein (HUP) has been found as a host factor of hypoxia screening but HUPs function largely is unknown. In this study, we found the Arabidopsis HUP26 gene which was conserved in different plant species and responded to various oxidative stress. HUP26 promoter analysis showed GUS activity in root and leaf tissues was significantly responsive to oxidative stress. HUP26-GFP is predominantly located in the cytoplasmic region. HUP26 overexpression results in altered enhanced pathogenesis-related gene 1 gene expression and reduced ion leakage levels compared with hup26 knockout and WT plants after inoculation with Pst DC3000. HUP26 overexpression transgenic plants showed improved resistance to Pst DC3000, but hup26 knockout plants exhibited increased susceptibility. Collectively, these results indicate that HUP26 plays important role in responses to various oxidative stress and confers biotic stress resistance. Engineering of HUP26 gene expression may represent a strategy to enhance biotic stress resistance of crops.