Alteration of plant defense pathways by effectors of the protist plant pathogen, Plasmodiophora brassicae
M. DJAVAHERI (1), H. Borhan (2), P. Haddadi (2), L. Ma (2), S. Rolfe (3), S. Strelkov (4), M. Links (2), W. Clarke (5), S. Robinson (2), I. Parkin (2) (1) AAFC, Canada; (2) Agriculture and Agri-Food Canada, Saskatoon Research and Development Centre, Canada; (3) University of Sheffield, United Kingdom; (4) University of Alberta, Canada; (5) New York Genome Centre, U.S.A.

Clubroot disease of Brassica crops is caused by the biotrophic parasite Plasmodiophora brassicae (Pb). Infection of canola (Brassica napus) by Pb stimulates gall formation on the roots, which results in significant yield loss in severely infected crops. P. brassicae resides entirely inside the plant cell, a feature that is unique among eukaryotic plant pathogens. The most virulent pathotype of Pb on canola in Canada is pathotype 3 (Pb3). We sequenced P3 ( reference genome) and Pb6 and re-sequenced Pb2, Pb5 and Pb8. Comparison of whole genome SNP profiles revealed that Pb2, 3, 5, 8 were highly similar and clustered as one group, while the SNP profile of Pb6 was more divergent. The haplotypes correlated with the host range and geographical distribution of these pathotypes, with Pb2, 3, 5, 8 being virulent on B. napus and present in the prairie provinces of Canada and Pb6 failing to cause disease on B. napus and being prevalent in British Columbia and Eastern provinces of Canada. The highly compact genome of Pb3 (24.2 Mbp with less than 2% repeats) consisted of 10,851 predicted genes, 300 of them encoding predicted small secreted proteins (SSPs). Over 20 candidates out of the 300 SSPs were selected (based on their expression profiles during B. napus infection) for in planta expression. Transient and stable transformation of a subset of SSPs in Nicotiana benthamiana and Arabidopsis thaliana revealed their function in suppression of PAMP-triggered immunity (PTI) as well as affecting plant growth and morphology. RNA-seq was employed to unravel effect of SSPs on gene expression of Arabidopsis transgenic lines.

Abstract Number: P11-351
Session Type: Poster