PHYSIOLOGICAL AND TRANSCRIPTOMIC CHANGES IN Brassica napus COTYLEDONS TREATED WITH SIRODESMIN PL PHYTOTOXIN

POMBO MA; ELLIOTT C; MAIALE SJ; ROSLI HG; ROMERO FM; GÁRRIZ A; RUIZ OA; IDNURM A; ROSSI FR

Congreso; XXXIII Argentinian meeting of plant physiology; 2021

Brassica napus (colza, canola) is the second-largest oilseed crop produced worldwide. Hemibiotrophic fungus Leptosphaeria maculans, is a devastating pathogen that causes blackleg disease in this plant species. Yield reduction and important economical losses are associated to infected plants because of a restriction in water and nutrient transport through the stem. It has been demonstrated that Sirodesmin PL is the major component of phytotoxic extracts produced by L. maculans and mutant isolates, unable to produce Sirodesmin PL, are less virulent on stems of B. napus. Nevertheless, the toxicity-mediating mechanisms are yet far from being understood. Here, we present results from global transcriptomic and physiological studies after treatment of B. napus cotyledons with Sirodesmin PL. Gene Ontology term enrichment of differentially expressed genes (DEGs) indicated that this toxin induced genes associated to different plant defense responses such as those involved in hormonal pathways, ROS accumulation and callose deposition. We also found that Sirodesmin PL suppressed genes associated to photosynthesis. In agreement with this, we corroborated that the whole photosynthetic activity was negatively affected by the treatment. Parameters associated with chlorophyll fluorescence and number of chloroplasts per cell were significantly lower in the spongy and palisade parenchyma of leaves treated with Sirodesmin PL. This study makes a significant contribution to understanding the molecular responses of B. napus to Sirodesmin PL, which could promote the development of effective strategies in L. maculans-resistance breeding programs.