Submitted to: International Society of Chemical Ecology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/17/2008
Publication Date: N/A
Technical Abstract: Fatty acid amino acid conjugates (FACs) in regurgitant of larval Spodoptera exigua1 were initially identified as plant volatile elicitors and research has been focused on this apparent ecological disadvantage rather than on possible benefit for the caterpillar itself. Recently, we demonstrated that N-linolenoyl- and N-linoleoyl-L-glutamine function as important intermediates that enhance the efficiency of nitrogen assimilation in S. litura larvae. This result might be best understood in the context of the lepidopteran larval stages that are thoroughly specialized morphology and ecology to maximized feeding, metabolism and growth. S. litura is one of the most notorious pests in Japan and efficient use of nitrogen resources is a vital issue for this phytophagous insects living on nitrogen-poor leaves. In this investigation we screened FACs through 26 lepidopteran species and found 17 of these species to have patterns of FACs in their gut contents that differed significantly from that of S. litura (??). Glutamine conjugates such as N-linolenoyl- and N-linoleoyl-L-glutamine seemed to be common to all these species, suggesting that these molecules are the primary structure of FACs. However, there were several additional evolutionary patterns based on acquirement of (i) glutamate conjugates, (ii) hydroxylated fatty acid conjugates, and (iii) both. Interestingly, hydroxylated FACs, including volicitin, were found only in Macrolepidoptera species (which are well developed and relatively big caterpillars), and most of which are vastly polyphagous. These results may give us a hint to understand the evolutionary interplay between a plants ability to detect and respond to different fatty acid amides and the insect’s dependence on these same compounds for maximized nitrogen assimilation.