The proteome study of germinated Puccinia triticina urediniospores reveals a novel effector protein required for virulence.

The obligate biotrophic fungus, Puccinia triticina (Pt), is a notorious plant pathogen known for wheat leaf rust disease that devastates global crop production annually. Pathogen-host interactions need to be elucidated, especially the identification of pathogen effectors contributing to virulence. ‘Omics’ strategies are an efficient tool set to study these pathogen-host interactions. No proteome data are available on the germlings stage of Pt, which could highlight proteins involved in the first interaction point between Pt and its host. Here, we have used a proteomics approach on germinated urediniospores of Pt to define the germling proteome. Using two-dimensional gel electrophoresis, 167 spots in the pI range of 4–7 were observed, from which 123 proteins were identified by tandem mass spectrometry. Further in silico characterization revealed that they were predominantly involved in metabolic and cellular processes, with six proteins annotated as candidate effectors. The candidate effector PTTG_06852, hereafter named as virulence factor 1 (PtVF1), was silenced by host-induced gene silencing (HIGS) to investigate its biological function. When the expression of PtVF1 was reduced by 78%, the infection severity was suppressed by 70%. The results demonstrate a significant impairment of virulence upon silencing, which validates PtVF1 as a virulence effector of Pt.