Mutualistic root endophytism of Sebacinales is not associated with the reduction of saprotrophic traits and requires a noncompromised plant innate immunity
G. LANGEN (1), U. Lahrmann (2), G. Jeena (1), H. Frerigmann (1), A. Zuccaro (1) (1) University of Cologne, Germany; (2) Fraunhofer Institute for Toxicology and Experimental Medicine, ITEM, Germany

During a compatible interaction, the sebacinoid root-associated fungi Serendipita indica (Piriformospora indica) and Serendipita vermifera (Sebacina vermifera) induce changes in root morphology and enhance shoot growth in Arabidopsis thaliana. Genomic traits of Sebacinales were revealed by Pfam analysis and compared with those of other root-associated fungi and saprotrophs. The transcriptional responses of S. indica, S. vermifera and of Arabidopsis roots to colonization were analyzed by custom-designed microarrays at three different symbiotic stages. We identified key genomic features characteristic of sebacinoid fungi, such as expansions for gene families involved in hydrolytic activities, carbohydrate-binding and protein–protein interaction. Additionally, we show that colonization of Arabidopsis correlates with the induction of salicylic acid catabolism and accumulation of jasmonate and glucosinolates (GSLs). Genes involved in root developmental processes were specifically induced by S. vermifera at later stages during interaction. Using different Arabidopsis indole-GSLs mutants and measurement of secondary metabolites, we demonstrate the importance of the indolic glucosinolate pathway in the growth restriction of S. indica and S. vermifera and we identify indole-phytoalexins and specifically indole-carboxylic acids derivatives as potential key players in the maintenance of a mutualistic interaction with root endophytes.

Abstract Number: P2-34
Session Type: Poster