The role of abiotic and biotic factors in glucosinolate changes in Brassicales

Abstract

In this work the glucosinolate (GSL) contents in edible plants and the response of GSL contents to biotic and abiotic stress were analyzed. Fluctuations in GSL contents in Nasturtium officinale were determined in the course of a growing season and in administered N. officinale during a human trial. Results showed only minor changes in GSL contents, which are similar during the development of N. officinale and cultivation of different batches. Hydrolysis of GSLs was analyzed in Moringa oleifera and potential breakdown products were discussed on the basis of structurally related GSLs. Glucosinolate changes were also investigated as a result of biotic stress. Higher contents of gluconasturtiin were observed in Brassica napus infected with Verticillium longisporum. Direct growth inhibitory aspects of gluconasturtiin-derived breakdown products were discussed. Infection of B. napus with Plasmodiophora brassicae on the other hand resulted in lower contents of GSLs. Regulation of gluconasturtiin biosynthesis by more virulent pathotypes might be the cause for differing contents between plants infected with pathotypes differing in their virulence. Furthermore, the influence of abiotic stress on GSL contents in plants was analyzed in this study. Rhythmic GSL fluctuations were observed in B. napus grown in light/dark and continuous light conditions and the influence of the expression of genes involved in biosynthesis and breakdown of GSLs were discussed. The influence of salt stress on Lepidium latifolium revealed significantly higher contents of the aliphatic GSL sinigrin, which might be involved in water homeostasis in the plant. Lastly, it was observed that drought stress resulted in higher contents of the indolic GSL glucobrassicin (GB) in Arabidopsis thaliana. The investigation of deuterium incorporation into GB revealed higher biosynthesis of GB during drought stress. The expression analysis of genes responsible for breakdown of GSLs and synthesis of indole-3-acetic acid (IAA) strongly suggests glucobrassicin as a source of IAA in drought-stressed plants.