Nicolas Dimopoulos, Darren Wong, Tegan Haslam, Rodrigo Lopez Gutierrez, Ljerka Kunst, and Simone Diego Castellarin*  
*The University of British Columbia, 2205 East Mall, Vancouver, BC V6T 1Z4, Canada (simone.castellarin@ubc.ca)

In grapes, the cuticle protects the berry from water loss, which may in turn affect the final berry size at ripening. Water deficit (WD) is a common stress in vine-yards, but little is known about how the berry cuticle is modified in response to this stress. Our previous work showed that the expression of some cuticle genes is modulated in grape berries exposed to water deficit stress. Furthermore, differen-tial expression and gene regulatory network analyses of grapevine RNA-seq datasets indicated that the cuticular wax biosynthetic pathway is differentially regulated during berry development and in response to environmental stresses, including water deficit. Thus, we hypothesize that in response to WD stress, the developing grape berry will modify the composition of cuticular waxes on the berry surface to reduce the rate of water loss. To study this question, we carried out experiments in 2015 and 2016 to characterize changes in transpiration and cuticular wax composition of developing Merlot berries in response to WD stress and found that the rate of water transpiration did not change in response to WD stress. Nevertheless, we expect changes in cuticular wax composition and in expression of cuticular wax biosynthetic genes in response to WD stress, since our experiment in 2015 indicated changes in berry wax composition. We are currently analyzing the wax composition and expression of key cuticular genes in the samples collected in 2016 to confirm our results.

Funding Support: Oregon Wine Board, Oregon Wine Research Institute