Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA 92093-0116, USA.
Development. 2010 Sep 1;137(17):2849-56. doi: 10.1242/dev.051748.
Plant axillary meristems are composed of highly organized, self-renewing stem cells that produce indeterminate branches or terminate in differentiated structures, such as the flowers. These opposite fates, dictated by both genetic and environmental factors, determine interspecific differences in the architecture of plants. The Cys(2)-His(2) zinc-finger transcription factor RAMOSA1 (RA1) regulates the fate of most axillary meristems during the early development of maize inflorescences, the tassel and the ear, and has been implicated in the evolution of grass architecture. Mutations in RA1 or any other known members of the ramosa pathway, RAMOSA2 and RAMOSA3, generate highly branched inflorescences. Here, we report a genetic screen for the enhancement of maize inflorescence branching and the discovery of a new regulator of meristem fate: the RAMOSA1 ENHANCER LOCUS2 (REL2) gene. rel2 mutants dramatically increase the formation of long branches in ears of both ra1 and ra2 mutants. REL2 encodes a transcriptional co-repressor similar to the TOPLESS protein of Arabidopsis, which is known to maintain apical-basal polarity during embryogenesis. REL2 is capable of rescuing the embryonic defects of the Arabidopsis topless-1 mutant, suggesting that REL2 also functions as a transcriptional co-repressor throughout development. We show by genetic and molecular analyses that REL2 physically interacts with RA1, indicating that the REL2/RA1 transcriptional repressor complex antagonizes the formation of indeterminate branches during maize inflorescence development. Our results reveal a novel mechanism for the control of meristem fate and the architecture of plants.
植物腋芽分生组织由高度组织化、自我更新的干细胞组成，这些干细胞产生不定芽或分化为花等结构。这些由遗传和环境因素决定的相反命运决定了植物种间结构的差异。Cys2-His2 锌指转录因子 RAMOSA1（RA1）在玉米花序、穗和穗颈的早期发育过程中调节大多数腋芽分生组织的命运，并且与草类结构的进化有关。RA1 或任何其他已知的 ramosa 途径成员（RAMOSA2 和 RAMOSA3）的突变会产生高度分枝的花序。在这里，我们报告了一个增强玉米花序分枝的遗传筛选，并发现了一个新的分生组织命运调节因子：RAMOSA1 增强子位点 2（REL2）基因。rel2 突变体显著增加了 ra1 和 ra2 突变体穗中长枝的形成。REL2 编码一种类似于拟南芥 TOPLESS 蛋白的转录共抑制因子，TOPLESS 蛋白在胚胎发生过程中维持顶端-基底极性。REL2 能够挽救拟南芥 top1 突变体的胚胎缺陷，表明 REL2 在整个发育过程中也作为转录共抑制因子发挥作用。我们通过遗传和分子分析表明 REL2 与 RA1 物理相互作用，表明 REL2/RA1 转录抑制复合物拮抗玉米花序发育过程中不定芽的形成。我们的结果揭示了控制分生组织命运和植物结构的新机制。
