EXPRESSION OF ARABIDOPSIS RESPONSE REGULATOR HOMOLOGS IS INDUCED BY CYTOKININS AND NITRATE

We examined cytokinin and nitrate responsiveness in gene expression of five distinct response regulator homologs (ARR3-ARR7) in the leaves o f nitrogen-starved Arabidopsis plants. The transcripts accumulated aft er spraying the shoots with t-zeatin, The induction of accumulation wa s highly specific for cytokinins. The transcripts also accumulated by supply of nitrate to the culture medium, These findings suggest that A RRs are involved in inorganic nitrogen signal transduction mediated by cytokinin as in the case of ZmCip1, a response regulator homolog rece ntly identified in maize. (C) 1998 Federation of European Biochemical Societies.