INVOLVEMENT OF CALCIUM AND CALMODULIN IN PROTEIN AND AMINO-ACID-METABOLISM IN RICE ROOTS UNDER ANOXIA

The pretreatment of rice roots for 1 h in aerobic conditions with the Ca2+-channel blockers ruthenium red (RR) and verapamil and the calmodu lin (CaM) antagonists N-(6-aminohexyl)-5-chloro-1-naphtylenesulfonamid e (W-7) and trifluoperazine, induced during 3 h of anoxia: (i) inhibit ion of amino acid and gamma-aminobutyric acid (Gaba) accumulation; (ii ) a decline in the protein content; (iii) a release of amino acids and K+ into the growth media. The calcium ionophore A23187 reversed these effects in RR-treated roots. Moreover, the aerobic pretreatment of ri ce roots with A23187 alone or CaCl2 increased the accumulation of amin o acids and Gaba. These data indicate that the Ca2+/CaM complex is inv olved in the transduction of an anaerobic signal by inhibiting proteol ysis and solute release, and activating the Ca2+/CaM-dependent glutama te decarboxylase.