Analysis of molecular mechanisms involved in the evolution of plant morphology

禾本科植物的花形态与典型的双子叶植物不同。为了更好地理解这种转移的分子基础，我们分离了RAP1A、RAP1B和RAG，它们分别是拟南芥A类基因APETALA1（AP1）和C类基因AGAMOUS（AG）的推定的水稻同源物。通过原位杂交分析了RAP1A、RAG和水稻B类基因同源基因OsMADS 2的表达模式。RAP1A mRNA在小穗发育的早期在花分生组织的顶端区域表达，然后在发育中的外稃、内稃和浆片中表达。OsMADS2转录本首先在雄蕊原基形成的区域被观察到。随后，OsMADS2 mRNA在浆片原基和雄蕊原基中出现，这种RNA积累模式一直持续到花发育后期。RAG在野生型幼穗的雄蕊和雌蕊中均有表达。这些RNA积累部分 ...更多信息 为了阐明禾本科植物的不育器官如浆片、外稃和内稃与双子叶植物花器官的进化关系，我们在水稻（Oryza sativa L.）AGAMOUS（AG）直系同源基因，在水稻植物中受肌动蛋白I启动子控制。总之，在26个独立的转基因株系中的18个中观察到浆片向雄蕊器官的转化。与发生在浆片中的几乎完全转化相反，没有转基因植物在内稃或外稃中表现出任何形态学改变。我们的研究结果证实了预测，浆片是一个相当于双子叶植物的花瓣，ABC模型可以应用于水稻至少在浆片和雄蕊的器官规格。另一方面，内稃或外稃的形态改变的情况下提出的可能性，ABC模型的简单应用到结构以外的浆片可能是无效的。少

The floral morphology of grass species is distinct from typical dicot plants. In order to achieve a better understanding of the molccular basis for this diversion, we isolated RAP1A, RAP1B and RAG, putative rice homologs for the Arabidopsis class A gene APETALA1(AP1) and class C gene AGAMOUS(AG), respectively. Expression patterns of RAP1A.RAG, and OsMADS2, a rice homolog of the class B gene, were analyzed by in situ hybridization. RAP1A mRNA was expressed in the apical region of the floral meristem at an early stage of spikelet development, and then its expression was localized in developing lemma, palea and lodicules. OsMADS2 transcript was first observed in the region where stamen primordia are formed. Soon after, OsMADS2 mRNA appeared in the lodicule primordia as well as stamen primordia and this RNA accumulation pattern persisted till late stages of floral development. The expression of RAG was observed in stamens and pistils of wild type young spikelets. These RNA accumulation pat … More terns are mostly similar to those of Arabidopsis class A, B, C genes supporting the notion that the ABC model may be extended to rice.In order to clarify the evolutionary relationship between grass sterile organs, such as lodicules, the lemma and the palea, and the dicot floral organs, we expressed RAG, a rice (Oryza sativa L.) AGAMOUS(AG) ortholog, in rice plants under the control of an Actin I promoter.As a consequence of the ectopic expression of the RAG, lodicules were homeotically transformed into stamens. In total, the transformation of lodicules to staminoid organs was observed in 18 out of 26 independent transgenic lines. In contrast to the almost complete transformation occurred in lodicules, none of the transgenic plants exhibited any morphological alterations in the palea or the lemma. Our results confirmed the prediction that the lodicule is an equivalent of a dicot petal and that the ABC model can be applied to rice at least for organ specification in lodicules and stamens. On the other hand, the absence of morphological alterations in the palea or the lemma raised the possibility that the simple application of the ABC model to structures outside the lodicules may not be valid. Less