Plant postembryonic development takes place in the meristems, where stem cells self-renew and produce daughter cells that differentiate and give rise to dif- ferent organ structures. For the maintenance of meri- stems, the rate of differentiation of daughter cells must equal the generation of new cells: How this is achieved is a central question in plant development. In the Arabidopsis root meristem, stem cells surround a small group of organizing cells, the quiescent center. Together they form a stem cell niche [1, 2], whose position and activity depends on the combinatorial action of two sets of genes—PLETHORA1 (PLT1) and PLETHORA2 (PLT2) [3, 4] and SCARECROW (SCR) and SHORTROOT (SHR) —as well as on polar auxin transport. In contrast, the mechanisms controlling meristematic cell differentiation remain unclear. Here, we report that cytokinins control the rate of mer- istematic cell differentiation and thus determine root- meristem size via a two-component receptor histidine kinase-transcription factor signaling pathway. Analy- sis of the root meristems of cytokinin mutants, spatial cytokinin depletion, and exogenous cytokinin applica- tion indicates that cytokinins act in a restricted region of the root meristem, where they antagonize a non- cell-autonomous cell-division signal, and we provide evidence that this signal is auxin.
Cytokinins determine Arabidopsis root meristem size by controlling cell differentiation / DELLO IOIO, Raffaele; LINHARES F., S; Scacchi, E; CASAMITJANA MARTINEZ, E; Heidstra, R; Costantino, Paolo; Sabatini, Sabrina. - In: CURRENT BIOLOGY. - ISSN 0960-9822. - 17:(2007), pp. 678-682. [10.1016/j.cub.2007.02.047]