Plant organs are produced in meristems in a continuous and predictable but nevertheless flexible manner. Phytohormones and transcription factors cooperate to balance meristem maintenance and organ production. Recent research has provided clues to the mechanisms underlying this cooperation. KNOTTED1-like homeobox (KNOX) and WUSCHEL (WUS) transcription factors facilitate high cytokinin activity in the shoot apical meristem (SAM), whereas high gibberellin and auxin activities promote the initiation of lateral organs at specific sites in the SAM flanks.
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We would like to thank Arnon Brand for the meristem SEM, Aya Shafir for advice on graphics, and Yuval Eshed, Zach Adam and members of the Ori lab for ideas, discussions and critical reading of the manuscript. Research on related topics in the Ori lab is supported by grants from the US–Israel Bi-national Agricultural Research and Development Fund (BARD, no. IS-3453-03) and the Israel Science Foundation (ISF no. 689/05).