Functional analysis of glucosinolate breakdown products in herbivory resistance of Brassica rapa

• Applicant: Dr. Katja Witzel
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448612257

Glucosinolates (GLS) and their hydrolysis products are an established example of constitutive plant defense mechanisms. However, due to the complexity of the individual compounds and the different herbivore preferences (specialist vs. generalist), their distinct roles in plant-herbivore interaction are far from being understood. This knowledge gap also hampers the breeding of herbivore-resistant Brassica crop cultivars. Field-testing of subspecies of Brassica rapa, a species encompassing a wide range of vegetables, was performed by the Russian project partner N. I. Vavilov All-Russian Research Institute of Plant Genetic Resources (VIR). Here, a clear preference pattern with regard to insect infestation was revealed. A wide variation of metabolites between subspecies was also determined, and correlations of the content of individual compounds between each other and with resistance to diseases and pests were found. The German project partner Leibniz Institute of Vegetable and Ornamental Crops (IGZ) previously demonstrated a high level of homogeneity with regard to subspecies-specific GLS pattern in a VIR core collection of B. rapa accessions originating from eight subspecies. However, a considerable variation in GLS hydrolysis product formation was found within the subspecies, which is mainly due to the differential action of specifier proteins. Specifier proteins channel the formation of epithionitriles, nitriles or, if absent, isothiocyanates, and play a central role in the breakdown of GLS into bioactive degradation products. We hypothesize that these proteins are major determinants in plant insect interaction. The aims of this proposed research are: 1) To survey the herbivore preference of 100 B. rapa accessions, originating from six subspecies, grown at three climatically different field stations in the Russian Federation2) To determine the level of congruence between natural field herbivory and artificial pest infestation 3) To assess the interrelation between field herbivory feeding behavior and secondary metabolite accumulation, especially GLS and GLS hydrolysis products 4) To identify and characterize yet unknown specifier proteins in B. rapa 5) To decipher the role of specifier proteins in plant-insect interaction6) To study how content and variability of secondary metabolites with protective function correlate with each other, and whether various biochemical protective mechanisms can be combined in one genotype.The results of this project will provide novel information on the role of GLS hydrolysis product diversification on plant-herbivore interaction. Moreover, by unravelling their impact, the targeted breeding of insect resistant Brassica crops will be possible.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Foundation for Basic Research, until 3/2022
• Cooperation Partner: Dr. Anna Artemyeva, until 3/2022