Characterisation of candidate effector proteins from barley pathogen Rhynchosporium commune

Abstract

Rhynchosporium commune causes leaf scald, one of the most devastating diseases of barley. It leads to significant yield losses, grain quality can also be affected, resulting in substantial losses for barley producers. Disease management strategies mainly rely on the use of fungicides and resistant varieties but R. commune populations can change rapidly, overcoming barley resistance and some fungicides. This study aimed for the characterisation of molecules released by R. commune during the interaction with its host barley. Analysis of transcripts produced by R. commune during infection of barley plants is a valuable resource for identification of pathogenicity factors. Sequencing of the interaction transcriptome from an early time point during barley infection with R. commune revealed three abundant transcripts coding for small secreted fungal proteins called RcCDI1, Rc2 and Rsu3_07158, this last one encoding for a hydrophobic surface binding protein. They are most highly up-regulated early during infection. RcCDI1 and its homologs from different fungal species exhibit PAMP activity. RcCDI1-triggered cell death was shown to require SGT1, SOBIR1 and BAK1 but was not suppressed by PiAVR3a, PexRD2, PexRD27 and AvrPto. Transient expression of truncated versions of RcCDI1 protein in N. benthamiana indicated that the N- and Cterminal domains of RcCDI1 are required for the induction of cell death. Identification of the plant receptor involved in RcCDI1 recognition in dicots will provide a valuable resource for engineering non-host resistance in monocots. The overexpression of Rc2 allele from R. commune strain L2A in the barley landrace SLB-10-009 induced necrotic lesions, indicating a potential recognition of the candidate effector Rc2. Virulence tests were performed to see whether single nucleotide polymorphisms (SNPs) in the gene sequence of Rc2 correlate with virulence/avirulence of the R. commune strains in the barley line SLB 10-009. Finally, targeted gene disruption was used as an approach to characterise RcCDI1, Rc2 and
Rsu3_07158 candidate effectors.

Date of Award	2017
Original language	English
Awarding Institution	University of Dundee
Supervisor	Anna Avrova (Supervisor), Paul Birch (Supervisor) & Juan Morales (Supervisor)