Coordinated Activation of Chitinase Genes and Extracellular Alkalinization in Suspension-cultured Tobacco Cells

Abstract

Rapid alkalinization of the culture medium in response to an elicitor was observed before the accumulation of transcripts of the chitinase genes. A correlation between the increase in extracellular pH and the induction of the chitinase genes was investigated. N, N'-Dicyclohexylcarbodiimide, an inhibitor of proton channels such as H⁺-ATPase, and carbonyl cyanide m-chlorophenylhydrazone, a protonophore, also induced the expression of basic class I and acidic class II chitinase genes and the rapid alkalinization of the culture medium. Both the alkalinization of the culture medium and the induction of the basic class I chitinase genes in response to the elicitor were inhibited by fusicoccin. These inhibitory effects were also observed by the treatment with staurosporine, and by the treatments with La³⁺ ions or Gd³⁺ ions. By contrast, the elicitor-inducible accumulation of transcripts of the acidic class II chitinase genes was not prevented in the presence of these inhibitors.