Analysis of molecular mechanisms involved in the evolution of plant morphology

禾本科植物的花形态不同于典型的双科植物。为了更好地了解这种转移的分子基础，我们分别分离了拟南芥a类基因aptala1 （AP1）和C类基因AGAMOUS（AG）的同源基因RAP1A、RAP1B和RAG。RAP1A的表达模式。利用原位杂交技术对RAG和水稻B类基因同源物OsMADS2进行了分析。RAP1A mRNA在小穗发育早期表达于花分生组织的顶端区域，随后在发育中的外稃、外稃和小叶中表达。OsMADS2转录本首次在雄蕊原基形成区域被观察到。不久之后，OsMADS2 mRNA出现在小叶原基和雄蕊原基中，这种RNA积累模式一直持续到花发育后期。RAG在野生型小穗雄蕊和雌蕊中表达。这些RNA积累模式与拟南芥A、B、C类基因的模式相似，支持了ABC模式可能扩展到水稻的观点。为了阐明禾本科不育器官（如茎节、外稃和古稃）与双子叶花器官之间的进化关系，我们表达了水稻（Oryza sativa L.）的RAG基因。AGAMOUS（AG）同源基因，在一个肌动蛋白I启动子控制下的水稻植株。由于RAG的异位表达，小泡同质转化为雄蕊。总的来说，在26个独立的转基因品系中，有18个品系观察到小泡向类胺器官的转化。与小叶几乎完全转化相反，转基因植株在古叶和外稃中没有表现出任何形态改变。我们的研究结果证实了小叶瓣相当于双梗花瓣的预测，ABC模型至少可以应用于水稻小叶瓣和雄蕊的器官规格。另一方面，古体或外稃中没有形态学改变，这提出了将ABC模型简单应用于小叶外结构可能无效的可能性。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