Effect of glucosinolate structure in Arabidopsis thaliana (L.) defense against caterpillars of a different feeding specialization

Effect of glucosinolate structure in Arabidopsis thaliana (L.) defense against caterpillars of a different feeding specialization All glucosinolates (GS) consist of a common core structure with variable side chains including aliphatic, aromatic, or indolic moieties. The aliphatic GS profiles of Arabidopsis thaliana (L.) HEYN. and other members of Brassicaceae are highly variable between different accessions of one species, but intra-specific studies give only limited insights into the impact of a particular GS structure in the plant defense against insects. Therefore, to analyze whether different lengths of aliphatic side chains confer divergent biological activities, caterpillars with generalist or specialist feeding behavior were fed on wild type plant lines of A. thaliana Columbia (WT) or those altered for the expression of MAM3 (mam3(+)). Based on the chemical profile, various mam3(+) lines were assigned to a C3 (five lines) or C7/C8 (seven lines) methylsulfinylalkyl GS phenotype and insect performance of those lines were compared to the mainly C4 methylsulfinylalkyl GS producing WT lines. While aliphatic levels in mam3(+) lines overall decreased compared to the WT due to a decrease of 4-methylsulfinylbutyl GS, indolyl GS contents were similar to WT. The percentage weight gain of the generalist caterpillar Spodoptera exigua (HUBNER) after three days was higher on the mam3(+) lines with lower aliphatic GS contents, but significantly higher only on mam3(+) C3 lines. By contrast, the percentage larval weight gain of the specialist Pieris brassicae L. was not significantly different on the three GS phenotypes. These results suggest that GS chain length can influence the plant resistance against unspecialized insects.