Protein phosphatase activities in wheat leaves

GISELLE MARTÍNEZ NOEL; TOGNETTI JORGE; PONTIS HORACIO

Hawai, USA

Congreso; ASPB; 2003

In addition to playing a central role in metabolism, soluble sugars help regulate many developmental and physiological processes in plants. Sugars have important hormone-like functions as primary messengers in signal transduction but the molecular mechanism underlying are largely unknown. In our laboratory we have shown that protein kinases and phosphatases play a role in sucrose induction of fructan metabolism in wheat leaves. Of the two components, kinases (PK) and phosphatases (PP), the first one has been studied intensively, while the second has only received lately more attention. We have previously demonstrated that okadaic acid blocks the induction of sucrose:fructan 6-fructosyl transferase mediated by sugars in wheat leaves, suggesting the participation of PP2A in the process as is the most sensitive phosphatase to the inhibitor. We have measure total soluble PP2A activity in extracts of wheat leaves treated with water (W) or with sucrose (Suc). No difference in activities were found in short term treatment (3 hs) but after 6 hs or longer times, PP2A activity decrease in plants treated with Suc. These findings led us to try to characterize the PP. We have submitted the extracts to ion exchange chromatography on DEAE-Sephacel followed by passage through Superose 12. Two peaks with PP activity were eluted in the first chromatography. Each peak on the gel filtration step unfold in two others. These results resemble those obtain with PP from animal origin indicating the presence of different subunits. Work is in progress to further characterize these proteins. Supported by ANPCyT and FIBA