Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)
Jeudi 31 mars 2016
Amphi 208 (Cœur d’École) à 14h
Study of plant and fungal cytokinins in the rice-Magnaporthe oryzae interaction
BPMP, Equipe Hormones, Nutriments et Développement
Cytokinins (CKs) are plant hormones known to participate in cellular and biological processes like cell division and nutrient partitioning. Their involvement in plant-pathogen interactions is an emerging feature. In a first part, I will present that exogenous application of the CK kinetin at an appropriate time before infection could increase rice resistance against the fungal pathogen Magnaporthe oryzae, which is the causal agent of the rice blast, the most devastating disease in rice. Furthermore, we isolated rice mutant lines which accumulated lower levels of the inactive CK cis Zeatin glucosides. Consistent with previous results, these mutant plants were more resistant to the rice blast and this could be associated to the enhanced expression of plant defenses observed in healthy plants. These results support a model where CKs produced during (or accumulated before) rice blast infection act synergistically in planta with the classical salicylic acid dependent-defense pathway to amplify resistance to M. oryzae. Magnaporthe and other plant pathogens have been shown to produce CKs but the function of this mimicry production by non-tumor inducing pathogens, has yet to be established. The second part is about the identification of a gene required for the fungal CK biosynthesis, CKS1, in Magnaporthe oryzae which is also highly conserved among fungi. Although cytokinin deficient strains (i.e. cks1 knock-out mutants) showed normal in vitro growth and development, they were severely affected for in planta growth and virulence. In addition, our results suggest that fungal-derived CKs are key effectors required for dampening host defenses and affecting sugar and amino acid distribution in and around the infection site. I will discuss the possible models explaining how CKs can favor (plant) resistance on one side and favor virulence (fungus) on the other.
Contact : Emilie Chanclud