Is a Key Regulator of Defense Responses to the Devastating Plant Pathogen in Oilseed Rape.

The disease caused by has traditionally been difficult to control, resulting in tremendous economic losses in oilseed rape (). Identification of important genes in the defense responses is critical for molecular breeding, an important strategy for controlling the disease. Here, we report that a mitogen-activated protein kinase gene, , plays an important role in the defense against in oilseed rape. is highly expressed in the stems, flowers and leaves, and its product is localized in the nucleus. Furthermore, is highly responsive to infection by and treatment with jasmonic acid (JA) or the biosynthesis precursor of ethylene (ET), but not to treatment with salicylic acid (SA) or abscisic acid. Moreover, overexpression (OE) of in and results in significantly enhanced resistance to , whereas resistance is diminished in RNAi transgenic plants. After infection, defense responses associated with ET, JA, and SA signaling are intensified in the -OE plants but weakened in the -RNAi plants when compared to those in the wild type plants; by contrast the level of both HO accumulation and cell death exhibits a reverse pattern. The candidate gene association analyses show that the BnaMPK3-encoding locus is a cause of variation in the resistance to in natural population. These results suggest that is a key regulator of multiple defense responses to , which may guide the resistance improvement of oilseed rape and related economic crops.