The shape and size of a plant cell can be determined by a variety of genetic and environmental factors, and involves an interplay between cell turgor and a regulated loosening of the surrounding cell wall or extracellular matrix. The regulation of sugar metabolism, uptake and transport also plays a central role in these growth processes. This project involves Arabidopsis receptor like protein kinases, the cell Wall Associated Kinases (WAKs), that are linked to pectin and are required for cell expansion. WAK attachment to pectin in the cell wall may be part of a mechanism that leads to the regulation of vacuolar invertase, and this in turn could influence turgor and hence cell expansion. Mutations in WAKs lead to a loss of cell expansion and in a wak2-1 mutant allele, a reduction of invertase activity in the vacuole. There are five WAKs in the Arabidopsis genome, and it has already been established that WAK2 is required for cell elongation and solute metabolism. The experiments will explore whether two other WAKs, WAK1 and WAK4 which are responsible for most of the remaining WAK activity in Arabidopsis, play the same role. The phenotypes of mutations in WAK1 and 4 will be explored by determining whether, like wak2-1, both sugars and salts are required for growth. A microscopic analysis will be used to determine if the mutations affect cell elongation. Enzyme activity and mRNA levels for key enzymes regulating solute metabolism will be measured to determine if the wak1 and wak4 alleles have the same affect as does the wak2-1 mutation. Thus it will be established whether other WAK family members have similar or distinct roles in cell expansion and plant development. These studies will explore fundamental events in cells that determine their shape and size, and thus architecture and function of plants. The research will be carried out at small liberal arts college, where undergraduate students will be provided with an integrative approach to science, and be prepared for the challenges of graduate and professional schools upon graduation.
