In Planta Effector Competition Assays Detect Hyaloperonospora arabidopsidis Effectors That Contribute to Virulence and Localize to Different Plant Subcellular Compartments

JORGE L. BADEL; DAVID GREENSHIELDS; SOPHIE J.M. PIQUEREZ; GANASHYAM RALLAPALLI; GEORGINA FABRO; NAVEED ISHAQUE; JONATHAN D. G. JONES

MOLECULAR PLANT-MICROBE INTERACTIONS

AMER PHYTOPATHOLOGICAL SOC

Lugar: St. Paul, Minessota; Año: 2013 vol. 26 p. 745 - 757

0894-0282

The genome of the pathogenic oomycete Hyaloperonosporaarabidopsidis is predicted to encode at least 134 high-confidenceeffectors (HaRxL) carrying the RxLR motif implicatedin their translocation into plant cells. However, onlyfour avirulence genes (ATR1, ATR13, ATR5, and ATR39)have been isolated. This indicates that identification ofHaRxL effectors based on avirulence is low throughput.We aimed at rapidly identifying H. arabidopsidis effectorsthat contribute to virulence by developing methods to detectand quantify multiple candidates in bacterial mixedinfections using either Illumina sequencing or capillaryelectrophoresis. In these assays, referred to here as inplanta effector competition assays, we estimate the contributionto virulence of individual effectors by calculatingthe abundance of each HaRxL in the bacterial populationrecovered from leaves 3 days after inoculation relative toabundance in the initial mixed inoculum. We identifiedHaRxL that enhance Pseudomonas syringae pv. tomatoDC3000 growth in some but not all Arabidopsis accessions.Further analysis showed that HaRxLL464, HaRxL75,HaRxL22, HaRxLL441, and HaRxL89 suppress pathogenassociatedmolecular pattern-triggered immunity (PTI) andlocalize to different subcellular compartments in Nicotianabenthamiana, providing evidence for a multilayered suppressionof PTI by pathogenic oomycetes and molecularprobes for the dissection of PTI.