Grapevine response to Planococcus ficus feeding

Plant response to insect feeding appears to be highly specific with regard to the organisms in the system. Here, we report on the interaction between grapevine Vitis vinifera plants and a phloem-feeding insect pest, the vine mealybug Planococcus ficus. Plants were exposed to P. ficus for periods of 6 hours and 96 hours, after which they were analysed for gene expression levels using microarrays and quantitative real-time PCR (qPCR). Both methods showed that grapevine displayed only a minimal response to mealybug feeding at the transcript level at both time periods. Intermediate grapevine exposure times (24, 48 and 72 hours) to P. ficus feeding were investigated using qPCR analysis of ten additional genes associated with known plant defense responses. Results showed that only a single gene, pathogenesis-related protein 1, was differentially expressed after 48 hours of mealybug feeding. During the course of mealybug feeding, however, a number of other genes were significantly up- or down-regulated at certain time points. Thus, it appears as if grapevine responds minimally to feeding by P. ficus as well as within a very narrow time period. The relative lack of grapevine plant defense mechanisms may be a result of the feeding strategies of mealybugs. Eight samples were analysed. Two replicates each were included for each treatment (6 hour and 96 hour feeding), resulting in four samples. Two control replicates were included for each treatment (6 hour and 96 hour feeding controls), resulting in a further four samples.