Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSPenetration-specific effectors from Phytophthora parasitica favour plant infection. Edouard Evangelisti 1* , Benjamin Govetto 2 , Naima Minet-Kebdani 1 ,Marie-Line Kuhn 1 , Agnes Attard 1 , Franck Panabieres 1 , Mathieu Gourgues 1 . 1) UMR Institut Sophia Agrobiotech, INRA/CNRS/Université de Nice, SophiaAntipolis, France; 2) Institut Méditerranéen de Biodiversité et d'Écologie marine et continentale (IMBE), CNRS-INEE - IRD -Aix Marseille Université -Université d'Avignon - Institut Pytheas.Oomycetes are major crop pests which cause million dollars losses every year. To date only a few efficient chemicals are available against thesefilamentous microorganisms. A better understanding of the molecular events occuring during plant-oomycete interactions will help to propose newstrategies for crop protection. We performed a transcriptional analysis in order to identify oomycete penetration-specific genes and identified a set ofpenetration-specific effectors (PSE) bearing a RXLR motif. This motif was previously shown to promote effector import into plant cells during the biotrophicstage in feeding structures called haustoria. Here we report the functional analysis of three candidate genes, referred to as PSE1, PSE2 and PSE3. The threeeffectors were able to abolish plant defense responses when transiently expressed in Nicotiana plants. Moreover, constitutive expression of PSE1 andPSE3 in A. thaliana led to an enhanced susceptibility to P. parasitica infection suggesting a role for these proteins in P. parasitica pathogenicity. TransgenicArabidopsis lines accumulating PSE1 protein showed several developmental perturbations that were associated with altered auxin physiology. Rootgrowth inhibition assays showed that auxin signaling pathway is not altered by PSE1 accumulation. Nevertheless, the coiled-root phenotype and theenhanced susceptibility of PSE1-expressing lines to P. parasitica were reverted by synthetic auxin 2,4-D supply, or treatment with the auxin efflux inhibitorTIBA suggesting that a reduced auxin accumulation is responsible for these phenotypes. This hypothesis was confirmed by a reduced activity of the pDR5auxin sensitive promoter at the root apex. The alteration of the expression pattern observed for two auxin efflux carriers, PIN4 and PIN7 suggests that aperturbation of auxin efflux could be responsible for the PSE1 associated defects. We proposed that PSE1 could favour P. parasitica virulence byinterfering with auxin content. Our results show that penetration specific effectors can modulate general plant functions to facilitate plant infection.Perturbation of hormone physiology was previously reported for other plant pathogens, including nematodes and bacteria, supporting the hypothesis thatinfection strategies from distant pathogens species could converge onto a limited set of plant targets.66