The galling parasite Daktulosphaira vitifoliae induces novel morphological change in Vitis

Galling parasites dramatically alter plant behavior, physiology, and morphology to enhance their fitness while reducing the health and productivity of the plant. To date, few parasite-plant modifications have been identified as physiologically important to the plant, and none have been directly linked to plant primary metabolism. We observed that gall formation in Vitis by the parasite, Daktulosphaira vitifoliae, induces adaxial stomatal formation adjacent gall openings. Vitis leaves are typically hypostomous, but gall induction creates adaxial stomata in increasing density with increasing proximity to the gall upwelling. These stomata are functional with intercellular air spaces that facilitate gas exchange to rapidly growing nutritive tissue. This observation is novel and, to our knowledge, has not been discussed previously in the context of benefit to the plant host or attacking parasite. Preliminary evidence suggests these stomata serve as an extended phenotype of the galling insect by enhancing the development of gall tissue. We are currently characterizing developmental gene expression and hormones to understand the mechanism regulating this phenomenon.