Characterisation of guided entry of tail-anchored proteins in Magnaporthe oryzae

Abstract

Rice (Oryza sativa L.) is one of the most important staple foods for human population worldwide. However, rice production continues to be severely threatened by rice blast disease caused by an ascomycete fungus Magnaporthe oryzae. Tail-anchored (TA) proteins are conserved across diverse organisms, and belongs to a class of polypeptides that are inserted into the membrane by a hydrophobic sequence located at the C- terminal region. The Guided Entry of Tail-anchored (GET) complex is responsible for the post-translational insertion of nascent TA proteins into the ER lipid bilayer. In Saccharomyces cerevisiae, the GET pathway comprises of six known associated components Get1, Get2, Get3, Get4, Get5, Sgt2 and Ssa1 that have been identified and extensively studied. However, the role of the GET complex in rice blast fungus has not been elucidated. Here in, we identified five proteins of the GET Complex in M. oryzae namely MoGet1, MoGet2, MoGet3, MoGet4 and MoSgt2 and generated the gene knock-out mutants. Deletion of MoGET1 and MoGET2 revealed that they are required for vegetative growth, asexual reproduction and pathogenesis, while MoGet3 negatively regulates hyphal growth, asexual development and pathogenesis of M. oryzae. In contrast, loss of MoGet4 and MoSgt2 had no effect on the normal development of the rice blast fungus. We demonstrated that the MoGet2 is important in osmotic stress response while MoGet2 and MoGet3 positively and negatively regulate cell wall integrity, respectively. The MoGet1 and MoGet2 were ER-localised and indispensable for DTT-induced ER stress response. In vitro and in vivo interaction assay revealed MoGet3 has physical interaction with both MoGet1 and MoGet2 indicating the existence of possible synergistic function amongst the Get components in rice blast fungus. In summary, this finding indicates the GET Components offers an excellent target for the development of antifungal components against recalcitrant plant fungal pathogens.