Protein Trafficking to the Plant Vacuolar Membrane
Research in our lab is focused on targeting mechanisms for plant tonoplast proteins using both classical genetic and chemical genetic approaches.
Tonoplast membrane transporters carry out the movement of molecules in and out of the plant vacuole including lipids, ions, sugars, hormones and defense molecules. The transport of molecules across the tonoplast is essential for plant vacuolar function, including the maintenance of cellular turgor and ion sequestration, which ultimately control osmotic potential of the cytosol. To improve plant stress tolerance and ultimately increase the nutritional value of plants for human consumption, it is essential that we understand how to regulate vacuolar trafficking of membrane proteins.
Novel inhibitors of tonoplast protein trafficking
In order to characterize trafficking pathways of tonoplast proteins, we identified chemical inhibitors that affect protein trafficking to the vacuole. One inhibitor, named C834, inhibits the targeting of the GFP-TIP2;1 marker protein to the tonoplast.
Using C834 treatments as well as other pharmacological tools, our group has shown that, in Arabidopsis, TIP3;1 and TIP2;1 are likely to use a Golgi-independent pathway, while TIP1;1 is likely to use a Golgi-dependent pathway. It is unknown at this point why these proteins are bypassing the Golgi, and how these closely related proteins are being targeted to each pathway.
C834 inhibits the targeting of the GFP-TIP2;1 marker protein to the tonoplast.
Novel regulators of tonoplast protein trafficking and vacuole biogenesis
With the goal of identifying proteins that regulate the trafficking pathway for TIP2;1, we have identified mutants in which these proteins are mis-localized. One of these mutants highlighted the role of a SNARE protein and phosphoinositides in vacuole fusion.
Loss of function alleles of VTI11 have many vacuoles per cell
We are currently characterizing the role of VTI11 SNARE in vacuole fusion during the development of the large central vacuole. This protein is critical for the normal morphology of the vacuole as evidenced by the mutant phenotypes of itt3, a new allele for this locus.