Cytosolic calcium requirement for fructan synthesis initiation

MARTÍNEZ-NOËL G; TOGNETTI J; PONTIS H

San Carlos de Bariloche

Congreso; XXXIX Reunión Anual SAIB; 2003

SAIB

In a previous work we have shown the involvement of protein kinases in the process that leads to the induction of fructan synthesis by sucrose in wheat. Experiments with the addition of specific Ser-Thr protein kinase inhibitors (staurosporine and W7), and cation chelating agents (EDTA, EGTA) strongly suggested the participation of calcium dependent protein kinases (CDPKs) in this process. Here we present further evidence of the role of Ca2+ in this sugar signaling cascade. The incubation of wheat tissues (root and leaf blades) with sucrose led to a rapid increase in cytosolic calcium (noticeable after 30 min), as shown by using a fluorescent probe (fluo3 AM). When blockers of calcium channels of either the plasmatic (LaCl3) or intracellular (ruthenium red) membranes were added, the sucrose response (induction of fructan synthesizing enzymes) was inhibited in dose-dependent manner (IC50= 0,19 mM and 1,15 ìM, respectively). On the other hand, calcium by itself did not mimic the induction effect of sucrose. The time course of calcium requirement seems to indicate that the signaling process takes place within 2-3 hrs after increased sucrose concentration in leaf tissues. In conclusion, our results suggest that cytosolic calcium is involved in this sucrose mediated signaling pathway, probably in relation with CDPK action. Supported by ANPCyT and FIBA.