Department of Plant Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.
Dev Cell. 2013 Feb 25;24(4):438-45. doi: 10.1016/j.devcel.2013.01.019.
Plant shoots display indeterminate growth, while their evolutionary decedents, the leaves, are determinate. Determinate leaf growth is conditioned by the CIN-TCP transcription factors, which promote leaf maturation and are negatively regulated by miR319 in leaf primordia. Here we show that CIN-TCPs reduce leaf sensitivity to cytokinin (CK), a phytohormone implicated in inhibition of differentiation in the shoot. We identify the SWI/SNF chromatin remodeling ATPase BRAHMA (BRM) as a genetic mediator of CIN-TCP activities and CK responses. An interactome screen further revealed that SWI/SNF complex components including BRM preferentially interacted with basic-helix-loop-helix (bHLH) transcription factors and the bHLH-related CIN-TCPs. Indeed, TCP4 and BRM interacted in planta. Both TCP4 and BRM bound the promoter of an inhibitor of CK responses, ARR16, and induced its expression. Reconstituting ARR16 levels in leaves with reduced CIN-TCP activity restored normal growth. Thus, CIN-TCP and BRM together promote determinate leaf growth by stage-specific modification of CK responses.
植物芽具有不定向生长的特性，而其进化后代——叶片则具有定向生长的特性。定向叶片生长受 CIN-TCP 转录因子调控，这些因子促进叶片成熟，并在叶片原基中受到 miR319 的负调控。本文中，我们发现 CIN-TCP 降低了叶片对细胞分裂素（CK）的敏感性，CK 是一种参与抑制芽中分化的植物激素。我们将 SWI/SNF 染色质重塑 ATP 酶 BRAHMA（BRM）鉴定为 CIN-TCP 活性和 CK 反应的遗传介质。相互作用组筛选进一步表明，SWI/SNF 复合物成分包括 BRM，优先与碱性螺旋-环-螺旋（bHLH）转录因子和相关的 CIN-TCPs 相互作用。事实上，TCP4 和 BRM 在体内相互作用。TCP4 和 BRM 均与 CK 反应抑制剂 ARR16 的启动子结合，并诱导其表达。在 CIN-TCP 活性降低的叶片中恢复 ARR16 水平可恢复正常生长。因此，CIN-TCP 和 BRM 共同通过特定阶段对 CK 反应的修饰来促进定向叶片生长。
