Analyse COI1-abhängiger Signalprozesse in Arabidopsis Wurzeln nach Infektion mit dem Pilzpathogen Verticillium longisporum
Organismische Interaktionen, chemische Ökologie und Mikrobiome pflanzlicher Systeme
Zusammenfassung der Projektergebnisse
The ascomycete Verticillium longisporum is a soil-borne vascular pathogen that causes major yield losses on rapeseed (Brassica napus). Our previous analysis of the V. longisporum/Arabidopsis thaliana interaction has unraveled that COI1, which is the receptor of the plant defense hormone jasmonoyl-isoleucine (JA-Ile), promotes disease. Unexpectedly, COI1 does not require JA-Ile for this disease-promoting function. Albeit COI1 does not affect fungal entry into the root, it is required in the root to promote propagation of the fungus in the shoot. In order to further elucidate this novel root-born COI1 function, next generation sequencing of RNA from mock-treated and infected coi1 (JA receptor mutant) and aos (JA biosynthesis mutant) was performed. Unexpectedly, V. longisporum-induced genes were not identified. Obviously, the plant cannot recognize the fungus in our axenic infection system that allows fungal entry into the root without wounding. Still, the analysis had unraveled that most of the genes that were differentially expressed in coi1 versus aos and wild-type showed elevated transcript levels in coi1 already in the uninfected state. Analysis of the relative transcript levels of two marker gene that are under the negative control of the JA-Ileindependent COI1 function showed that known components of the jasmonate signaling pathway like NINJA, MYC2/MYC3/MYC4 or EIN3/EIL1 are not operating downstream of this novel COI1 function. No conclusive data were obtained about the role of JAZ proteins. RNAseq analysis performed with uninfected and infected soil-grown coi1 and aos plants showed, that most of the genes that are up-regulated in coi1 are induced by V. longisporum. This may suggest that the coi1-mediated tolerance is due to pre-induction of a specific set of genes. The identification of a master regulator of this program might give information on strategies to confer tolerance to V. longisporum.
