ASGSB 1999 Annual Meeting Abstracts

IN VITRO PHOSPHORYLATION EVENTS DURING GROWTH AND GRAVITROPISM IN ZEA MAYS ROOTS AND A POSSIBLE ROLE OF STATHMIN. T.J. Mulkey and D.A. Prentice. Department of Life Sciences, Indiana State University, Terre Haute, IN

The relay-phosphoprotein, stathmin (also known as pp17, prosolin, Op18, p17, P19, pp20, pp21, pp23, and 19-K), is an approximately 19-kDa cytosolic protein implicated in signal transduction mechanisms. Twelve phosphorylated and two unphosphorylated forms of stathmin have been identified in animal systems. We have identified several stathmin-like protein forms in maize roots by Northern blots. The activity of the stathmin-like protein in roots can be altered by treatment with EDTA, calcium, indole-3-acetic acid (IAA), tetradeconoyl phorbol-13-acetate (TPA), and staurosporine. Alteration of the activity of the stathmin-like protein modifies growth rates and gravitropic curvature of intact maize roots. Inhibition of the phosphorylation of stathmin-like proteins decreases the growth rate of vertically oriented roots. Activators of the phosphorylation of stathmin-like proteins increase the growth rate of vertically oriented roots. Activators of stathmin-like protein phosphorylation can mimic auxin activity in vertical and graviresponding roots of maize. These data suggest a possible role of stathmin-like proteins in regulating auxin-mediated motor response of gravitropism through the second messenger system through which auxin regulates growth in the elongating region of the root. Further characterization of the role of stathmin as a possible regulator of signal transduction events during root gravitropic response and elongation will be presented.

Back to Meeting Program