An ER-anchored Enzyme of GhIRE1 Negatively Responding to Salt Tolerance in Gossypium Hirsutum L.

IRE1 is an endoplasmic reticulum (ER)-resident sensor and performs as a crucial regulator in the response to adverse conditions. Previous studies have focused on the function of IRE under drought and heat stress, but how IRE1 participates in salt stress is not clear. In this study, silencing the IRE1a and IRE1b genes in Gossypium hirsutum exhibited increased tolerance to salt stress compared to WT plants. Moreover, Arabidopsis thaliana overexpressing two splice variants of GhIRE1a, s1 and s2, showed different phenotypes under salt stress conditions. The overexpression of s1, which contains two domains (kinase and endoribonuclease domains), negatively regulated salt tolerance, while s2, which contains one kinase domain, did not affect the salt tolerance of Arabidopsis thaliana, suggesting that IRE1 negatively regulated salt tolerance. Cotton seedlings treated with STF-083010, which is a chemical inhibitor of IRE1 endoribonuclease, displayed reduced H2O2 contents and increased activity of GST, TPX and TRXR, suggesting that inhibition of IRE1 endoribonuclease confers salt tolerance by decreasing H2O2 contents in Gossypium hirsutum. Collectively, our results revealed the essential function of GhIRE1 in the salt stress response, in which GhIRE1 plays a vital role by regulating ROS under salt stress.