Effects of adenine and cytokinins on growth and protein kinase activity of Verticillium albo-atrum.

Growth of Verticillium albo-atrum in liquid Czapek-Dox broth was stimulated about four-fold by added 10 mM adenine, N6-benzyladenine, or kinetin. Less stimulation was evident at lower concentrations. With none of these included in the basal growth medium, detectable protein kinase activity in cell-free extracts was low and responded minimally to cAMP (adenosine 3',5'-cyclic monophosphate) in the reaction mixture. With each of these compounds as an additive to the growth medium, protein kinase activity was not only greater but also responded markedly (several fold) to cAMP. These results demonstrate a strong correlation between exogenously supplied adenine and related compounds, increased growth, increased protein kinase activity, and kinase response to cAMP in this organism.