[Indole butyric acid activates Ca2+-ATPase in Malus hupehensis Rhed. roots by protein phosphorylation].

The effect of IBA on protein kinase and Ca(2+)-ATPase activity of Malus hupehensis Rhed. roots were studied by adding 3, 3', 4', 5, 7-pentahydroxyflavone (quercetin), a protein kinase inhibitor, and IBA into the Hagland nutrient solution at different time. The results showed that membrane protein phosphorylation in roots occurred mainly on the serine residues. After treatment of Malus hupehensis Rhed.roots with 100 mumol/L IBA, the activity of protein kinase and Ca(2+)-ATPase increased several dozens of times in 2-3 h and then decreased rapidly after they reached the vertex. The protein kinase activity changes earlier than that of Ca(2+)-ATPase. Quercetin not only inhibits the protein kinase activity, but also weakens the activation of Ca(2+)-ATPase by IBA markedly. It is suggested that Ca(2+)-ATPase may be a member of IBA signal transduction in M. hupehensis roots and IBA activates Ca(2+)-ATPase activity through protein phosphorylation.