TRANSCRIPTOMIC ANALYSIS REVEALS THE ACTION MECHANISM OF SIRODESMIN PL TOXIN IN BRASSICA NAPUS.

POMBO. MARINA; ELLIOTT, CANDACE; ROSLI, HERNAN; ROMERO, FERNANDO M.; GARRIZ, ANDRES; RUIZ, OSCAR; IDNURM, ALEXANDER; ROSSI, FRANCO RUBÉN

Congreso; Congreso conjunto SAIB-SAMIGE; 2020

Brassicanapus (colza, oilseedrape) is currently the second-largest produced oilseed crop worldwide. Like mostcrops, B. napus is continuouslyexposed to a myriad of microorganisms. Phoma stem canker (also known as the Blacklegdisease) is caused by a complex of Leptosphaeriaspecies (L. maculans and L. biglobosa), and is one of the most importantdiseases of B. napus and otherBrassica species. This disease results in important economic losses eachseason, as it reduces yield by restricting water and nutrient transport throughthe stem, resulting in premature senescence. It has been demonstrated that someplant pathogenic fungi can produce secondary metabolite toxins as part of amultifaceted strategy to increase its infection and virulence in plants.Sirodesmin PL is the major component of the phytotoxic extracts produced by L. maculans. This toxin is a member ofthe epipolythiodioxopiperazine (EPTs) class of fungal secondary metabolites,which are characterized by a sulphur-bridged dioxopiperazine ring. Thedisulphide bridge allows ETPs to cross-link proteins via cysteine residues, andto generate reactive oxygen species through redox cycling. It has beendemonstrated that L. maculans mutantsunable to produce Sirodesmin PL are less virulent on stems of B. napus. Previously, we showed thatSirodesmin PL requires functional thiols for its toxicity and that it modifiesthe redox status in B. napuscotyledons. Nevertheless, the toxicity mechanisms of this toxin are yet farfrom being understood. Here, we present results from a global transcriptomic studyafter the treatment of B. napuscotyledons with Sirodesmin PL. Changes in the transcriptome were analyzed at 16and 48 hours post-treatment. In this way, the amount of up-regulateddifferentially expressed genes (DEGs) were larger than those downregulated atboth times post-treatment. To identify the biological processes, molecularfunctions and cellular components that are affected by Sirodesmin PL treatment,we performed Gene Ontology (GO) term enrichment on upregulated anddownregulated DEG sets. Biological process related to cellular nitrogencompound metabolism, amine metabolism, oxidation-reduction process, sulphur compoundmetabolism, and transmembrane transport were upregulated. On the other hand,biological processes related to photosynthesis, chlorophyll biosynthesis,carbohydrate metabolism, and oxidation-reduction process were downregulated. Finally,several genes involved in the biosynthesis and signaling of plant defensehormones, including jasmonic acid and ethylene, were upregulated afterSirodesmin PL treatment. This study makes a significant contribution tounderstand the molecular responses of B.napus to Sirodesmin PL for the development of effective strategies in L. maculans-resistance breeding.