ALISON DeLONG Ph.D., Harvard University 1989 Assistant Professor MCB Graduate Program 401-863-3888 [email protected]

We are using molecular and genetic approaches to gain insight into the mechanisms that control plant growth and development. A large number of plant signal transduction pathways have been shown to involve reversible protein phosphorylation events that regulate key steps in development, as well as responses to the environment. A rapidly growing body of evidence shows that the activities of protein phosphatases make important contributions to the regulatory circuitry controlling cell biology and development, and that protein phosphatase activities themselves are tightly regulated. Our goal is to gain insight into the function of protein phosphatase 2A (PP2A), an enzyme that performs important roles in phosphorylation cascades governing cell proliferation, morphogenesis and cell fate. Our current research focuses on elucidating the biological functions of PP2A in Arabidopsis thaliana, a 'model species' for which a wealth of molecular genetic tools and techniques have been developed, and for which a completed genome sequence is now available.

My laboratory is using both dominant-defective and loss-of-function approaches to study PP2A functions in Arabidopsis. Our analysis of one PP2A mutant has already shown that PP2A activity plays a role in regulating plant responses to gravity, a major environmental cue for plant growth. Genetic experiments also suggest a role for PP2A in embryogenesis. Our ongoing studies are focused on determining the mechanism through which PP2A activity influences these processes, using analytical tools provided by biochemistry and cell biology as well as molecular biology and genetics.

We are also using a functional genomics approach to isolate new PP2A mutants, to identify additional signal transduction and growth control roles of PP2A. Another area of interest is the use of dominant-defective PP2A mutations to study PP2A functions. Characterizing the phenotypes of transgenic plants expressing dominant-defective PP2A alleles will increase our understanding of PP2A function in cell division, pattern formation and differentiation. We have undertaken similar experiments with human PP2A genes, with the long-term goal of assessing the roles of PP2A in the regulation of proliferation.

Publications

DeLong, A., K. Mockaitis and S. Christensen (2002) Protein phosphorylation in the delivery of and response to auxin signals. Plant Mol Biol. 49: 285-303.

Muday, G.K. & A. DeLong (2001) Polar auxin transport: Controlling where and how much. Trends in Plant Science 6: 535-542.

Rashotte, A. M., A. DeLong & G. K. Muday (2001) Genetic and chemical reductions in protein phosphatase activity alter auxin transport, gravity response and lateral root growth. The Plant Cell 13: 1683-1697.

Lizotte, D., D. D. McManus, H. R. Cohen, & A. DeLong (1999) Functional expression of human and Arabidopsis protein phosphatase 2A in Saccharomyces cerevisiae and isolation of dominant-defective mutants. Gene 234: 35-44.

Deruère, J., K. Jackson, C. Garbers, D. Söll & A. DeLong (1999) The RCN1-encoded A subunit of protein phosphatase 2A increases phosphatase activity in vivo. Plant Journal 20: 389-399.

Garbers, C., A. DeLong, J. Deruère, P. Bernasconi & D. Söll (1996) A mutation in Protein Phosphatase 2A Regulatory Subunit A Affects Auxin Transport in Arabidopsis. EMBO J. 15: 2115-2124.