| This research investigated early transcriptional responses of the model legume, Medicago truncatula, to herbivory by caterpillars of the beet armyworm, Spodoptera exigua. Differentially expressed genes were identified by the differential display technique, cDNA-amplified fragment length polymorphism (cDNA-AFLP). To distinguish between caterpillar-specific responses and general wound responses, a subset of plants was mechanically damaged. Furthermore, to identify responses to salivary elicitors, plants were subject to herbivory by caterpillars with normal salivary secretions and those that had their spinneret, the appendage through which labial saliva is secreted, cauterized shut. Eighteen differentially expressed gene fragments, representing 16 genes, were identified. The expression pattern of 5 of these genes was analyzed by Northern analysis, confirming a caterpillar-specific reduction in transcripts encoding rubisco activase and glyceraldehyde-3-phosphate dehydrogenase. This research shows that plants are able to differentiate between caterpillar herbivory and mechanical damage and that transcriptional response are initiated within one hour after caterpillar infestation. |
