The rice heterochronic gene SUPERNUMERARY BRACT regulates the transition from spikelet meristem to floral meristem
The rice heterochronic gene SUPERNUMERARY BRACT regulates the transition from spikelet meristem to floral meristem
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DOI：
10.1111/j.1365-313x.2006.02941.x
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发表时间：
2007-01-01
期刊：
影响因子：
7.2
通讯作者：
An, Gynheung
中科院分区：
文献类型：
--
作者：
Lee, Dong-Yeon;Lee, Jinwon;An, Gynheung
分生组织身份转换的调控是生殖发育的关键步骤。茎尖分生组织（SAM）在获得花序分生组织的同一性后，依次向二级和高级分生组织过渡，最终形成花器官。尽管对SAM向花序分生组织转变的分子机制有充分的了解，但对花序，特别是单子房花序发育的机制知之甚少。本文报道了控制小花分生组织向花分生组织过渡和花器官发育的SUPERNUMERARY BRACT （SNB）基因的鉴定。该基因编码一个携带两个AP2结构域的转录因子。SNB:GFP融合蛋白定位于细胞核。SNB在所有被检测的组织中表达，但在新出现的小穗分生组织中表达最强烈。在SNB基因敲除的植物中，从小穗分生组织到花分生组织的转变被延迟，导致在另一种叶根分类中产生多个初级颖片。额外苞片的发育干扰了随后的花结构。在一些小穗，空颖片和小叶被转化成外稃/古样器官。偶尔，雄蕊和心皮的数量发生改变，小穗轴的腋部出现异位小花。这些表型表明snb是一个异时突变体，影响小穗分生组织的相变、花器官的模式形成和小穗分生组织的决定性。
Regulating the transition of meristem identity is a critical step in reproductive development. After the shoot apical meristem (SAM) acquires inflorescence meristem identity, it goes through a sequential transition to second- and higher-order meristems that can eventually give rise to floral organs. Despite ample information on the molecular mechanisms that control the transition from SAM to inflorescence meristems, little is known about the mechanism for inflorescence development, especially in monocots. Here, we report the identification of the SUPERNUMERARY BRACT (SNB) gene controlling the transition from spikelet meristem to floral meristem and the floral organ development. This gene encodes a putative transcription factor carrying two AP2 domains. The SNB:GFP fusion protein is localized to the nucleus. SNB is expressed in all the examined tissues, but most strongly in the newly emerging spikelet meristems. In SNB knockout plants, the transition from spikelet meristems to floral meristems is delayed, resulting in the production of multiple rudimentary glumes in an alternative phyllotaxy. The development of additional bracts interferes with subsequent floral architecture. In some spikelets, the empty glumes and lodicules are transformed into lemma/palea-like organs. Occasionally, the number of stamens and carpels is altered and an ectopic floret occurs in the axil of the rachilla. These phenotypes suggest that snb is a heterochronic mutant, affecting the phase transition of spikelet meristems, the pattern formation of floral organs and spikelet meristem determinancy.