Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
Dev Cell. 2012 Jan 17;22(1):211-22. doi: 10.1016/j.devcel.2011.10.026.
The cell types of the plant root are first specified early during embryogenesis and are maintained throughout plant life. Auxin plays an essential role in embryonic root initiation, in part through the action of the ARF5/MP transcription factor and its auxin-labile inhibitor IAA12/BDL. MP and BDL function in embryonic cells but promote auxin transport to adjacent extraembryonic suspensor cells, including the quiescent center precursor (hypophysis). Here we show that a cell-autonomous auxin response within this cell is required for root meristem initiation. ARF9 and redundant ARFs, and their inhibitor IAA10, act in suspensor cells to mediate hypophysis specification and, surprisingly, also to prevent transformation to embryo identity. ARF misexpression, and analysis of the short suspensor mutant, demonstrates that lineage-specific expression of these ARFs is required for normal embryo development. These results imply the existence of a prepattern for a cell-type-specific auxin response that underlies the auxin-dependent specification of embryonic cell types.
植物根的细胞类型首先在胚胎发生早期被特化，并在植物的整个生命周期中保持不变。生长素在胚胎根起始中起着至关重要的作用，部分是通过 ARF5/MP 转录因子及其生长素不稳定抑制剂 IAA12/BDL 的作用。MP 和 BDL 在胚胎细胞中起作用，但促进生长素向相邻的胚外悬浮细胞（包括静止中心前体（下胚轴））的运输。在这里，我们表明，该细胞内的自主生长素反应对于根分生组织的起始是必需的。ARF9 和冗余的 ARFs 及其抑制剂 IAA10 在悬浮细胞中起作用，介导下胚轴的特化，并且令人惊讶的是，也阻止向胚胎身份的转化。ARF 的过表达和短悬浮突变体的分析表明，这些 ARF 的谱系特异性表达对于正常的胚胎发育是必需的。这些结果表明，存在一种细胞类型特异性生长素反应的预模式，它是生长素依赖性胚胎细胞类型特化的基础。
