The Requirements for Ca^<2+>, Protein Phosphorylation, and Dephosphorylation for Ethylene Signal Transduction in Pisum sativum L.

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The role of Ca^<2+> and protein phosphorylation in the transduction of the ethylene signal resulting in induction of 1-aminocyclopropane-1-carboxylic acid (ACO oxidase has been studied in peas (Pisum sativum L.) by a pharmacological approach. 2,5-Norbornadiene (NBD) and aminoethoxyvinylglycine (AVG) reduced the basal level of ACC oxidase transcript and its enzyme activity. Only NBD was shown to inhibit the ethylene response, the accumulation of ACC oxidase transcript and the stimulation of its enzyme activity. Ethylene influenced ^<45>Ca^<2+> influx into the segment tissues from pea epicotyls, and ethylene glycol-bis(β-aminoethyl ether)N,N,N,N′N′-tetraacetic acid (EGTA), a Ca^<2+> chelator, inhibited the ethylene response. Ca^<2+> depletion by pretreatment with EGTA also blocked the ethylene response, which almost completely recovered when Ca^<2+> was added exogenously after Ca^<2+> depletion. Ca^<2+> channel blockers, verapamil, and LaC1_3, used to certify the role of extracellular Ca^<2+>, all inhibited the ethylene response. A protein kinase inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), and protein phosphatase inhibitors, vanadate and okadaic acid, also inhibited the ethylene response. The results of the present study suggest that Ca^<2+> influx from the extracellular space, protein phosphorylation, and dephosphorylation are required for the induction of ACC oxidase by ethylene.
日本植物生理学会の論文