Title : Investigating the biological roles of sinigrin hydrolysis products on insect herbivory in Brassicaceae
Abstract:
The glucosinolate-myrosinase system is an important defence mechanism in the Brassicaceae family, producing hydrolysis products such as isothiocyanates and nitriles, which play a significant role in insect-plant interactions. However, the biological function of epithionitriles remains unexplored. This study investigates the effects of two distinct hydrolysis products of sinigrin namely allyl isothiocyanate (AITC) and 1-cyano-2,3-epithiopropane (CETP) from Lepidium latifolium, a high altitude plant on two specialist herbivores, Pieris brassicae and Plutella xylostella. To corroborate these findings in a natural environment, the formation of AITC and CETP during different developmental stages of Lepidium latifolium was quantified and used in bioassays. AITC at variable concentrations increased the herbivory by two fold in P. brassicae larvae compared to the control. In contrast, CETP at the same concentration reduced herbivory by over six fold. Larval faecal metabolite analysis revealed the accumulation of toxic compounds in larvae fed with CETP, indicate the incomplete metabolic processing of CETP. Similar deterrent effects of CETP were observed in P. xylostella larvae suggests the broad-spectrum deterrent activity of CETP. The significant reduction in larval feeding on CETP highlights its potential as a natural insect repellent, offering a sustainable strategy to minimize pesticide usage in Brassica crop protection.
