Identification of Phytophthora Crinklers (CRNs) with RNA silencing suppression activity
Y. ZHAI (1), W. Ma (2), E. Huitema (3) (1) University of California, Riverside, U.S.A.; (2) Department of Plant Pathology and Microbiology and Center for Plant Cell Biology, University of California, Riverside, U.S.A.; (3) Division of Plant Sciences and College of Life Sciences, University of Dundee, United Kingdom

Phytophthora contains many important plant pathogens that cause devastating diseases of crops. Genome sequences of Phytophthora revealed hundreds of cytoplasmic effectors that function inside the plant cells to enhance virulence. Recent findings suggested that Phytophthora produces RxLR effectors with RNA silencing suppression activity. Here, we explored the Crinklers (CRNs), another family to cytoplasmic effectors that are widely distributed in oomycetes, for their ability to suppress small RNA silencing in plants. Using a functional screen, we identified two CRNs from Phytophthora capsici that can suppress transgene silencing in Nicotiana benthamiana. Leaves expressing GFP and the CRNs showed reduced abundances of GFP siRNAs, suggesting that these CRNs could interfere with small RNA accumulation. This activity was further confirmed using transgenic Arabidopsis plants expressing individual CRNs. Interestingly, both CRNs are localized in the nucleus of plant cells, indicating that they may directly affect plant gene expression in the transcription or post-transcription level. Function of CRNs is an under-studied area compared to RxLR effectors although they are considered a more ancient effector family in oomycetes. Phylogenic analysis showed these two CRNs had homologs present in other Phytophthora species as well as in oomycete animal pathogens. Further analysis on the mechanism by which these CRNs affect small RNA silencing and their virulence function will be discussed.

Abstract Number: P9-329
Session Type: Poster