Regulation of cell wall remodeling in grapevine (Vitis vinifera L.) callus under individual mineral stress deficiency created by João C. Fernandes, Luis F. Goulao and Sara Amâncio

Cell wall (CW) is a dynamic structure that determines the plant form, growth and response to environmental conditions. Vitis vinifera callus grown under nitrogen (−N), phosphorous (−P) and sulfur (−S) deficiency were used as a model system to address the influence of mineral stress in CW remodeling. Callus cells morphology was altered, mostly under –N, resulting in changes in cell length and width compared with the control. CW composition ascertained with specific staining and immuno-detection showed a decrease in cellulose and altered pattern of pectin methylesterification. Under mineral stress genes expression from candidate families disclosed mainly a downregulation of a glycosyl hydrolase family 9C (GH9C), xyloglucan transglycosylase/hydrolases (XTHs) with predicted hydrolytic activity and pectin methylesterases (PMEs). Conversely, upregulation of PMEs inhibitors (PMEIs) was observed. While methylesterification patterns can be associated to PME/PMEI gene expression, the lower cellulose content cannot be attributed to altered cellulose synthase (CesA) gene expression suggesting the involvement of other gene families. Salt extracts from –N and −P callus tissues increased plastic deformation in cucumber hypocotyls while no effect was observed with −S extracts. The lower endo-acting glycosyl hydrolase activity of −N callus extracts pinpoints a more expressive impact of −N on CW-remodeling.