Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8657, Japan.
Plant J. 2012 Apr;70(2):327-39. doi: 10.1111/j.1365-313X.2011.04872.x. Epub 2012 Jan 13.
Post-embryonic development depends on the activity of meristems in plants, and thus control of cell fate in the meristem is crucial to plant development and its architecture. In grasses such as rice and maize, the fate of reproductive meristems changes from indeterminate meristems, such as inflorescence and branch meristems, to determinate meristems, such as the spikelet meristem. Here we analyzed a recessive mutant of rice, aberrant spikelet and panicle1 (asp1), that showed pleiotropic phenotypes such as a disorganized branching pattern, aberrant spikelet morphology, and disarrangement of phyllotaxy. Close examination revealed that regulation of meristem fate was compromised in asp1: degeneration of the inflorescence meristem was delayed, transition from the branch meristem to the spikelet meristem was accelerated, and stem cell maintenance in both the branch meristem and the spikelet meristem was compromised. The genetic program was also disturbed in terms of spikelet development. Gene isolation revealed that ASP1 encodes a transcriptional co-repressor that is related to TOPLESS (TPL) in Arabidopsis and RAMOSA ENHANCER LOCUS2 (REL2) in maize. It is likely that the pleiotropic defects are associated with de-repression of multiple genes related to meristem function in the asp1 mutant. The asp1 mutant also showed de-repression of axillary bud growth and disturbed phyllotaxy in the vegetative phase, suggesting that the function of this gene is closely associated with auxin action. Consistent with these observations and the molecular function of Arabidopsis TPL, auxin signaling was also compromised in the rice asp1 mutant. Taken together, these results indicate that ASP1 regulates various aspects of developmental processes and physiological responses as a transcriptional co-repressor in rice.
胚胎后发育依赖于植物分生组织的活性，因此分生组织中细胞命运的控制对植物发育及其结构至关重要。在水稻和玉米等禾本科植物中，生殖分生组织的命运从不定向分生组织（如花序和侧芽分生组织）转变为定向分生组织（如小穗分生组织）。在这里，我们分析了水稻隐性突变体 aberrant spikelet and panicle1 (asp1)，该突变体表现出多种表型，如分支模式紊乱、小穗形态异常和叶序排列混乱。仔细观察发现，asp1 中分生组织命运的调节受到了损害：花序分生组织的退化被延迟，从侧芽分生组织向小穗分生组织的转变被加速，侧芽分生组织和小穗分生组织中的干细胞维持受到损害。小穗发育的遗传程序也受到干扰。基因分离表明，ASP1 编码一种转录共抑制子，它与拟南芥中的 TOPLESS (TPL)和玉米中的 RAMOSA ENHANCER LOCUS2 (REL2)有关。很可能是多效缺陷与 asp1 突变体中与分生组织功能相关的多个基因的去抑制有关。asp1 突变体还表现出侧芽生长的去抑制和营养期叶序紊乱，表明该基因的功能与生长素作用密切相关。与这些观察结果和拟南芥 TPL 的分子功能一致，水稻 asp1 突变体中的生长素信号也受到损害。综上所述，这些结果表明，ASP1 作为水稻中的转录共抑制子，调节着发育过程和生理反应的各个方面。
