Unravelling the Hyaloperonospora parasitica effectors complement functions

GEORGINA FABRO; RITA LEI; ALEJANDRA ROUGON-CARDOSO; DAVID STUDHOLME; JONATHAN D G JONES

Keystone, Colorado, USA

Simposio; Plant Hormones and Signalling and Plant Innate Immunity, Keystone Symposia; 2008

Keystone Symposia

Many plant pathogens secrete effector molecules that once delivered into the host can manipulate cellular responses and suppress defences, enabling the parasite to complete its life cycle. Hyaloperonospora parasitica (Hp) is an oomycete obligate biotroph that infects A. thaliana . It has co-evolved with its host and is unable to infect other plant species. Two Hp effectors that are recognized by the host in a race-specific manner have being reported (ATR1, Rehmany et al., 2005; ATR13, Allen et al., 2004). These and other oomycete spp. effectors are secreted proteins containing an RXLR motif necessary for delivery into host plant cells (Whisson et al., 2007). Our first aim is to identify, clone and assay in planta at least 100 putative effectors of this pathogen based on the preliminary assembly of Hp race Emoy2 genome (www.vbi.vt.edu). For this screening, we use the EDV system of Hp effector delivery through Pseudomonas syringae TTSS (Pst) (Sohn et al., 2007). Currently, we have identified 134 candidate effectors (RXLR EEs and not EEs). We have selected those candidates that were expressed during the infection process by sequencing ESTs of a 3dpi cDNA library (www.454.com) and short reads of a 7dpi sequence tag library www.illumina.com . We have cloned 31 Hp candidate effectors in the Pst-EDV system, and we are in the process of cloning 44 more. In a joint effort with our collaborators we estimate we will reach 130 soon. 16 candidate effectors have been tested in planta, and 9 of them confer enhanced bacterial virulence and/or suppress PAMP triggered immunity related responses on different (3 to 12)