Local and systemic changes in squash gene expression in response to silverleaf whitefly feeding

Squash genes (SLW1 and SLW3) induced systemically after silverleaf whitefly feeding were identified. Differences in the local and systemic expression of SLW1 and SLW3 after feeding by the closely related silverleaf and sweetp otato whiteflies were observed. Temporal and spatial studies showed that SL W1 and SLW3 were induced when second, third, and fourth nymphal instars wer e feeding. Although only barely detected after wounding and bacterial infec tion, SLW1 and SLW3 RNAs were abundant during water-deficit stress. Treatme nts with wound/defense signal molecules showed that SLW1 RNAs accumulated i n response to methyl jasmonate and ethylene, whereas SLW3 was not regulated by known wound/defense signals, suggesting utilization of a novel mechanis m for defense signal transduction. SLW1 RNAs accumulated during floral and fruit development, whereas SLW3 RNAs were not detected during vegetative or reproductive development. The potential roles of SLW1, an M20b peptidase-l ike protein, and SLW3, a beta-glucosidase-like protein, in defense and the leaf-silvering disorder are discussed.