Responses of Arabidopsis thaliana plant lines differing in hydroxylation of aliphatic glucosinolate side chains to feeding of a generalist and specialist caterpillar

Plants contain variable chemical compositions which play a role in direct defense against phytophagous insects. Glucosinolates (GSs) are the predominant secondary metabolites and defense compounds in brassicaceous species. As a consequence of co-evolution between adapted crucifer-feeding specialists and their associated host-plants, specific plant insect interactions have developed in a divergent manner from non-adapted generalists. Therefore, generalist and specialist insects may provoke different insect-inducible plant responses. Here, we have investigated the specific biochemical and molecular plant responses of Arabidopsis thaliana (L) induced by the generalist Spodoptera exigua (Hubner) and the specialist Pieris brassicae L To get more detailed information about herbivore-mediated-specific plant responses in different chemotypes within one species, we used multiple plant lines with either the non-hydroxylated 3-methylsulfinylpropyl GS or the hydroxylated 3-hydroxypropyl GS in a comparable genetic background. Caterpillar feeding induced a stronger GS accumulation in the 3-hydroxypropyl GS chemotype than the 3-methylsulfinylpropyl GS chemotype, considering the overall insect-mediated changes in aliphatic and indole GS levels in all lines. Herbivory by the generalist S. exigua and the specialist P brassicae had similar effects on biochemical and transcriptional response pattern. Contrary to the paradigm that specialists may minimize the induction of chemical defenses, we observed a higher elicitation of GSs by the specialist species. The accumulation of especially 1-methoxy-indol-3-ylmethyl GS and the induced gene transcripts by the two species point to an insect-mediated activation of the jasmonic acid signaling pathway in the plant lines. (C) 2012 Elsevier Masson SAS. All rights reserved.