ROS accumulation and associated cell death mediates susceptibility to Alternaria brassicae in Arabidopsis accessions

Abstract

Alternaria brassicae is a necrotrophic fungal pathogen capable of infecting most of the agriculturally important Brassica species. The mechanisms underlying invasion of A. brassicae and host responses are unknown. In the present study, we exploited the natural variation in Arabidopsis to understand the molecular and cellular mechanisms underlying resistance to A. brassicae. Using a subset of resistant (Ei-2, Ull2-3, Lz-0, and Cvi-0) and susceptible (Gre-0, Est-1, and Zdr1) accessions, we show that the susceptibility to A. brassicae is associated with higher ROS accumulation and cell death. Susceptibility to A. brassicae was reduced in the rboh (D, E and F) mutants that are incapable of producing ROS, suggesting that RBOH D, E and F may act as negative regulators of defence against this pathogen. Additionally, our data also supports the hypothesis that the Jasmonic acid (JA), Ethylene (ET) and Abscisic acid (ABA) signalling pathways positively contribute to resistance against necrotrophic pathogens. In summary, these results reveal the central role of ROS and cell death in the pathogenesis of A. brassicae and expand our understanding of plant-necrotroph interactions.

Functional characterisation of the Nep1-like protein effectors of the necrotrophic pathogen - Alternaria brassicae

“…Previous studies on the infection of A. brassicae have identified two critical time points viz. 2 and 4 days post infection [6], therefore we studied the expression of AbrNLP1 and AbrNLP2 at these time points. We found that both AbrNLP1 and AbrNLP2 are expressed in vitro i.e.…”

“…Cell death (either necrotic or apoptotic-like) plays a central role in plant-pathogen interactions either by restricting pathogen growth (in case of biotrophs) or by providing a nutrient source for the proliferation of the pathogen (in case of necrotrophs). Many well-known necrotrophic pathogens such as Botrytis cinerea, Sclerotinia sclerotiorum, Alternaria brassicae have been shown to induce cell death in the host and effective induction of cell death leads to susceptibility [6-8].…”