Cytokinin-induced changes in CLAVATA1 and WUSCHEL expression temporally coincide with altered floral development in Arabidopsis

Application of the cytokinin N6-benzylaminopurine (BAP) to the shoot apical meristem of Arabidopsis thaliana Landsberg erecta (L.) Heynh. induced aberrant flower development, including an increase in floral organ number resembling the clavata (clv) mutant phenotype. Transcriptome analysis of BAP-treated populations indicated that expression of CLV1, a gene encoding a receptor-like kinase involved in organ differentiation and stem-cell maintenance in shoot and floral apical meristems, was significantly reduced by the exogenous cytokinin. Time course analysis by RT-PCR of transcript levels in BAP-treated plants during flower development showed a decline and subsequent recovery of CLV1 and a concurrent increase in WUSCHEL (WUS), consistent with the known suppression of WUS by CLV. WUS encodes a homeodomain protein linked to shoot meristem proliferation. The temporal coincidence of aberrant floral phenotype with changes in transcript levels of CLV1 and WUS suggests that cytokinins regulate flower development through genes controlling shoot apical meristem activity.