GhCPK33 Negatively Regulates Defense against <i>Verticillium dahliae</i> by Phosphorylating GhOPR3

Abstract

<i>Verticillium</i> wilt, caused by the soil-borne fungus <i>Verticillium dahliae</i>, is a destructive vascular disease in plants. Approximately 200 dicotyledonous plant species in temperate and subtropical regions are susceptible to this notorious pathogen. Previous studies showed that jasmonic acid (JA) plays a crucial role in plant-<i>V. dahliae</i> interactions. <i>V. dahliae</i> infection generally induces significant JA accumulation in local and distal tissues of the plant. Although JA biosynthesis and the associated enzymes have been studied intensively, the precise mechanism regulating JA biosynthesis upon <i>V. dahliae</i> infection remains unknown. Here, we identified the calcium-dependent protein kinase GhCPK33 from upland cotton (<i>Gossypium hirsutum</i>) as a negative regulator of resistance to <i>V. dahliae</i> that directly manipulates JA biosynthesis. Knockdown of <i>GhCPK33</i> by <i>Agrobacterium tumefaciens</i>-mediated virus-induced gene silencing constitutively activated JA biosynthesis and JA-mediated defense responses and enhanced resistance to <i>V</i> <i>dahliae</i> Further analysis revealed that GhCPK33 interacts with 12-oxophytodienoate reductase3 (GhOPR3) in peroxisomes. GhCPK33 phosphorylates GhOPR3 at threonine-246, leading to decreased stability of GhOPR3, which consequently limits JA biosynthesis. We propose that GhCPK33 is a potential molecular target for improving resistance to <i>Verticillium</i> wilt disease in cotton.