Parcy François, Bomblies Kirsten, Weigel Detlef
Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
Development. 2002 May;129(10):2519-27. doi: 10.1242/dev.129.10.2519.
The Arabidopsis transcription factor LEAFY acts upstream of homeotic genes such as AGAMOUS to confer floral identity on meristems that arise after the transition to reproductive development. Compared to the genetic circuitry regulating the establishment of floral meristem identity, little is known about its maintenance. Previous experiments with leafy heterozygous plants and agamous mutants grown in conditions that reduce the floral inductive stimulus have shown that both genes are required to prevent reversion of floral to inflorescence meristems. Here, we present evidence that LEAFY maintains floral meristem identity independently of AGAMOUS, and that the primary role of LEAFY is either direct repression of shoot identity genes or repression of an intermediate factor that activates shoot identity genes. The latter conclusions were deduced from the phenotypes conferred by a gain-of-function transgene, LEAFY:VP16, that appears to act as a dominant negative, or antimorphic, allele during maintenance of floral meristem identity. These observations contrast with previous findings that LEAFY acts as a direct activator of floral homeotic genes, supporting the hypothesis that the transcriptional activity of LEAFY is dependent on specific co-regulators.
拟南芥转录因子LEAFY在诸如AGAMOUS等同源异型基因的上游起作用，赋予向生殖发育转变后产生的分生组织花的特征。与调节花分生组织特征建立的遗传回路相比，对其维持了解甚少。之前对在降低花诱导刺激条件下生长的leafy杂合植物和agamous突变体进行的实验表明，这两个基因对于防止花分生组织逆转为花序分生组织都是必需的。在此，我们提供证据表明LEAFY独立于AGAMOUS维持花分生组织特征，并且LEAFY的主要作用要么是直接抑制茎特征基因，要么是抑制激活茎特征基因的中间因子。后一个结论是从功能获得型转基因LEAFY:VP16赋予的表型推导出来的，该转基因在花分生组织特征维持期间似乎作为显性负等位基因或反形态等位基因起作用。这些观察结果与之前LEAFY作为花同源异型基因的直接激活剂的发现形成对比，支持了LEAFY的转录活性依赖于特定共调节因子的假说。
