Altering the Glucosinolate Profile of Arabidopsis thaliana: Characterization and Impact on Resistance Against Botrytis cinerea

Abstract

The glucosinolate-myrosinase system is a well-known part of the Brassicacea plant immunity. This family includes several important crop species as well as the model organism Arabidopsis thaliana, thus encouraging and facilitating extensive research on this field. The glucosinolate-myrosinase system in A.thaliana involves a plethora of glucosinolates that through myrosinase activity is hydrolyzed to bioactive compounds with potential antimicrobial activities. The glucosinolate composition of A.thaliana differs between tissues, and rosette leaves are dominated by methionine derived aliphatic glucosinolates and tryptophan derived indolic glucosinolates. Throughout the last decades, the role of the majority of genes involved in glucosinolate biosynthesis have been revealed, thus allowing for an intentional alteration of the glucosinolate profiles and investigation of its impact. In the current study we characterized several mutants and transgenic lines intended to alter the length (MAM1 k.o) or structure (ALK overexpression) of the aliphatic glucosinolate side chain and assessed the impact of these alterations on pathogen resistance. ESP overexpression lines intended to alter the hydrolytic activity of myrosinase did expectedly not display an altered glucosinolate profile. However, a suspected silencing of ESP was observed, and the hydrolysis product profiles of these lines were not characterized. Despite the expected change in the glucosinolate profiles of the mam1 and ALK-lines, as well as additional increase in aliphatic glucosinolate content in the ALK-lines, no clear and consistent alterations in resistance towards Botrytis cinerea were observed. Through conducting growth experiments under both long day (16h light) and short day (10h light) conditions, we found an increase in indolic glucosinolate amounts in plants grown under long day conditions suspected to be caused by expression level increase of MYB51.