A rapid cytokinin response assay in Arabidopsis indicates a role for phospholipase D in cytokinin signalling.

Seedlings of Arabidopsis thaliana harboring a fusion of the cytokinin-responsive ARR5 gene promoter and the GUS reporter gene were used for a pharmacological approach to study cytokinin signal transduction. The assay was shown to be rapid, sensitive, dose-dependent and highly specific for cytokinins, both adenine and phenylurea derivatives. Numerous inhibitors of known signalling pathways were tested and some were shown to suppress reporter gene induction. Particularly, primary alcohols that specifically inhibit phospholipase D (PLD) partially prevented cytokinin-induced GUS activity and reduced the accumulation of ARR5 gene transcripts. This indicates a role for PLD early during cytokinin signalling.