Mesophyll cells from the leaves of Zinnia elegans, when cultured in a medium containing a specific ratio of auxin to cytokinin, directly transdifferentiate into tracheary elements. Cells pass through an irreversible point of determination during this process and I have identified both proteins that are secreted into the medium at the point of determination, as well as some cDNAs whose expression appears to be determination-dependent.
My project will be to understand the nature and function of the corresponding genes and products in the determination events at both a molecular and a cellula level. Further work on the differential screening of cDNA libraries will allow me to define marker for stages of determination and subsequent differentiation.
A focus of my work would be on a 87kDa protein that I have identified as being a major secreted protein only at the point of determination under inductive conditions. Immuno-screening of expression libraries will enable me to characterise the corresponding cDNA and will allow me to examine the expression and function of this protein both in intact plants and at key stages of determination in culture. If time permits the work will expand into two areas, characterisation of genomic clones and a search for homologues in Arabidopsis in order to generate transgenic plants for over- and under-expression of the corresponding message.
The project will involve training in a wide variety of cell biological, immunological biochemical and molecular biological techniques, and will help me to begin to understand the molecular basis for cell determination in plant development.