Analyzing the Hyaloperonospora arabidopsidis effector¡¯s effects

GEORGINA FABRO; SOPHIE PIQUEREZ; DAVID GREENSHIELDS; JONATHAN D G JONES

Asilomar, California, USA

Congreso; Oomycete Molecular Genetics Network Meeting 2009; 2009

Oomycete Molecular Genetics Network

The oomycete Hyaloperonospora arabidopsidis (Hpa) is an obligate biotroph of A. thaliana. Hparequires living host tissue for growth and reproduction. The pathogen uses a wide range of effectors togain access to resources available in its host, and at the same time avoid or suppress host defenceresponses. These effectors are predominantly small secreted proteins containing signal peptide and RxLRmotifs. Bioinformatic analysis of the Hpa Emoy2 race genome was carried out and ≈ 140 potentialeffectors were identified. In a shared effort with the ERA-PG Consortium, 102 effectors have beencloned. We analyzed the complement of Hpa effectors for (i) Functions in virulence /avirulence in A.thaliana (ii) Genetic variation in the host for their recognition. For this, we used a Heterologous (EDV)System delivering one effector at the time via the Pseudomonas syringae (Pst) TTSS (Sohn et al., PlantCell 2007). Using different modified Psts (LUX and ΔCEL) we could assess if a given Hpa effector couldincrease or decrease bacterial growth ?in planta?, and suppress PAMP triggered immunity (PTI).Preliminary results indicate that 88% of the 61 effectors tested can enhance bacterial growth on at leastone A.t. accession, and of these 55% do so in 3 to 5 more accessions. 18% of the tested effectors canrestrict bacterial growth, and some of these provoke HR-like lesions on specific A.t. accessions. Also,50% of the effectors can suppress callose accumulation when delivered through Pst ΔCEL, indicating PTIsuppression. Mixed infections using sets of Psts carrying different effectors are also being developed andresults will be presented.