The role of terpenes produced by Brassica napus in interactions with Verticillium longisporum

Abstract: Verticillium longisporum is responsible for severe yield losses, especially of oilseed rape (Brassica napus). Rapeseed is the third most important source of vegetable oil worldwide. The need to increase rapeseed oil yield is not only because is a source of healthy vegetable oil but also because it is used as a biodiesel. The control of Verticillium longisporum has been limited since this pathogen forms special resting structures that survive in the soil for a long time and under harsh environment, showing also delayed expression of symptoms. Volatile secondary metabolites exuded by plant roots have been involved in plant-plant and plant-herbivore signalling, while they affect fungal behaviour. For example, monoterpenes display strong inhibitory or stimulatory activities on fungi. Previous analysis showed that a group of V. longisporum genes are highly induced during application of monoterpenes. In this study, RT-qPCR analysis of V. longisporum genes exposed to terpenes produced by rapeseed plants, previously identified by RNAseq analysis upon infection of rapeseed showed to be induced. Consistent with the previous results, the Arabidopsis monoterpene mutant AT5G44630 (sesquiterpene synthase) was more tolerant to Verticillium infection, suggesting an involvement of this gene in disease development. An in vitro experiment showed that fungal biomass was lower in mutant Arabidopsis lines compared to the wild type (WT) plants. Finally, to produce rapeseed resistant plants to V. longisporum a clustered regulatory interspaced short palindromic repeats (CRISPR/Cas9) construct to was generated to produce rapeseed plants lacking the homologous AT5G44630 gene.