The barley powdery mildew effector protein ROPIP1 is encoded on an active retroelement
M. NOTTENSTEINER (1), R. Hückelhoven (1) (1) Chair of Phytopathology, Center of Life and Food Sciences Weihenstephan, TU München, Germany

We identified Rho of plants (ROP)-interacting peptide 1 (ROPIP1) as Blumeria graminis f.sp. hordei (Bgh) virulence effector. ROPIP1 directly interacted with the barley susceptibility factor HvRACB in yeast and in planta and was required for full virulence of Bgh on barley. Noticeably, ROPIP1 is encoded on an abundant non-long terminal repeat retroelement in the highly repetitive genome of Bgh. A native ROPIP1 protein was shown on western blots and observed to be secreted and translocated from the fungus into barley epidermal cells by immunogoldlabelling. Here, we present first steps into an analysis of the retroelement that encodes ROPIP1.The ROPIP1 sequence aligned to the 5’-end of the retroelement, followed by an apparently degraded short-interspersed element (SINE)-like region. However, it differs from SINE elements in its architecture and its obvious transcription by RNA polymerase II. Some manually inspected genomic insertions showed chimeric ROPIP1 ORFs that equipped the ROPIP1 sequence with predictable secretory signal peptides. Our results suggest the neofunctionalization of a Bgh retroelement transcript into an effector protein of Bgh. Together with a recent report on Bgh effector proteins having evolved from autonomous long-interspersed elements (LINEs), this may suggest retroelement transcripts as an additional source of effector evolution in the highly repetitive genome of Bgh.

Abstract Number: P9-291
Session Type: Poster