BnaMPK3 Is a Key Regulator of Defense Responses to the Devastating Plant Pathogen Sclerotinia sclerotiorum in Oilseed Rape

Abstract

The disease caused by Sclerotinia sclerotiorum has traditionally been difficult to control, resulting in tremendous economic losses in oilseed rape (Brassica napus). 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 B. napus mitogen-activated protein kinase gene, BnaMPK3, plays an important role in the defense against S. sclerotiorum in oilseed rape. BnaMPK3 is highly expressed in the stems, flowers and leaves, and its product is localized in the nucleus. Furthermore, BnaMPK3 is highly responsive to infection by S. sclerotiorum 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 BnaMPK3 in B. napus and Nicotiana benthamiana results in significantly enhanced resistance to S. sclerotiorum, whereas resistance is diminished in RNAi transgenic plants. After S. sclerotiorum infection, defense responses associated with ET, JA, and SA signaling are intensified in the BnaMPK3-OE plants but weakened in the BnaMPK3-RNAi plants when compared to those in the wild type plants; by contrast the level of both H2O2 accumulation and cell death exhibits a reverse pattern. The candidate gene association analyses show that the BnaMPK3-encoding BnaA06g18440D locus is a cause of variation in the resistance to S. sclerotiorum in natural B. napus population. These results suggest that BnaMPK3 is a key regulator of multiple defense responses to S. sclerotiorum, which may guide the resistance improvement of oilseed rape and related economic crops.

TALEN-Based HvMPK3 Knock-Out Attenuates Proteome and Root Hair Phenotypic Responses to flg22 in Barley

“…Both kinases also regulate ethylene production at the same conditions via phosphorylation of 1-amino-cyclopropane-1-carboxylic acid synthase ( Han et al, 2010 ), and positively regulate expression of many defense-related genes (including basic endochitinase) by phosphorylation of ERF6 transcription factor upon B. cinerea infection ( Meng et al, 2013 ). Thus, Arabidopsis MPK3 and MPK6, as well as their homologues in other species confer resistance to pathogens in dicots and monocots ( El Sarraf et al, 2019 ; Kim et al, 2019 ; Liu et al, 2019 ; Wang et al, 2019 ).…”

Recent Advances in Mechanisms of Plant Defense to Sclerotinia sclerotiorum

“…It has been shown that WRKY33 can be phosphorylated by MPK3/MPK6 in vivo in response to the pathogen infection in A. thaliana , which may be a hint for the release of WRKY33. A recent study has shown that B. napus MPK3 is a key regulator in defense responses to S. sclerotiorum (Wang et al, 2019).…”

“…This can be explained by the new model depicting the lifestyle transition of the pathogen from biotrophic to necrotrophic growth (Kabbage et al, 2015), because it has been suggested that the SA signaling protects against biotrophs, while JA/ET signaling activates defense responses against necrotrophs (Penninckx et al, 1996; Thomma et al, 1998; Glazebrook, 2005), as well as herbivorous insects (Howe and Jander, 2008; War et al, 2012). In favor of a role of ET signaling in this defense, is the recent discovery that B. napus MPK3, a positive regulator of ET signaling, positive regulates resistance to S. sclerotiorum (Wang et al, 2019).…”

The Notorious Soilborne Pathogenic Fungus Sclerotinia sclerotiorum: An Update on Genes Studied with Mutant Analysis

“…S. sclerotiorum is a highly damaging pathogen with diverse infection modes and a double feeding lifestyle of both biotroph and necrotroph ( Figure 1) [6,7]. It attacks host plants either by means of ascospores that can be discharged forcibly upwards from apothecia into the air, or by mycelium arising from infected tissue or from germinated sclerotia [8].…”

“…For major crop diseases, the most welcoming and environmentally friendly control method is through the use of resistant cultivars. However, strong host single-gene resistance has not been found against S. sclerotiorum [12], which makes it difficult to improve resistance using classical breeding methods [7]. Even with mild resistance, the traits seem to be multigenic.…”