FaesAG基因参与调控甜荞雌雄蕊异型分化的分子机制

Common buckwheat (Fagopyrum esculentum, Polygonaceae), a pseudo-cereal with healing benefits, has a short vegetative period with dimorpic stamen and gynoecium. Buckwheat possesses a dimorpic flowers, with populations being equally composed of plants with pin flowers (long pistil and short stamens) and plants with thrum flowers (short pistil and long stamens). Moreover, they are strictly self-incompatible with obligate cross-pollination between pin and thrum flowers,which make it an excellent model for studying developmental dimorpic flower-fate specification. Our study revealed that FaesAG plays a central role in specifying stamen and carpel identity in buckwheat, and encodes a MADS-box transcription factors. In addition, the functions of the genes are highly correlated with their expression zones. In combination of various methods and techniques, the proposal aims to document the FaesAG gene differential expression between thrum and pin flower development, and uncover the molecular mechanisms of FaesAG invovling in dimorphic stamen and gynoecium specification. Moreover, the upstream genes regulating the tancription of the FaesAG and they working together to specify the stamen and gynocium development are discussed. The results should provide valuable information to understand the flower evolution of the Fagopyrum spp. Moreover, it should also provide suitable candidate genes for genetic improvement and cross breeding in buckwheat.

甜荞（Fagopyrum esculentum）是蓼科（Polygonaceae）药食兼用的非禾谷类作物，其株系中thrum型（短花柱长雄蕊）和pin型（长花柱短雄蕊）花按1：1分离，自花或同型花之间授粉不亲和，成为研究植物雌、雄蕊异型分化调控的理想材料。同时，其雌、雄蕊异型分化又限制了荞麦品系间精准杂交。项目组在研究甜荞花型调控中发现：FaesAG基因具有参与调控甜荞雌、雄蕊正常发育的重要功能。本项目拟从该基因入手，系统研究其参与甜荞thrum型和pin花雌、雄蕊异型分化调控过程。在此基础上，分析上游关键转录因子FaesAP2_1和FaesAP2_2对FaesAG基因转录调控的差异，及FaesAG基因协同其他雌、雄蕊特征决定转录因子调控甜荞雌、雄蕊异型分化的分子过程。解析FaesAG基因参与调控甜荞雌、雄蕊异型分化的分子机制。为甜荞的分子改良、杂交育种与荞麦属植物的花型演变研究积累资料。

甜荞（Fagopyrum esculentum）是蓼科（Polygonaceae）荞麦属药食兼用且具有二型花的非禾谷类作物，其群体中thrum型（短花柱长雄蕊）和pin型（长花柱短雄蕊）花植株按1：1分离，自花或同型花间授粉不亲和，异型花间仅等高的柱头和花药间授粉才能正常结实，自然结实率低、杂交育种困难；另甜荞仅具有3轮花器官的结构与多数双子叶植物具典型4轮花器官的结构明显不同，成为研究植物花型演化，雌、雄蕊异型分化调控的理想材料。结合同源克隆、RNA-seq和RACE技术，分别从甜荞中分离出FaesAG、FaesAP1、FaesAP2_1和FaesAP2_2基因。蛋白序列同源比对和分子系统发育分析显示：FaesAG属核心真双子叶植物中C类MADS-box家族中的euAG进化系转录因子，FaesAP1属核心真双子叶植物中A类MADS-box家族中的euAP1进化系转录因子，FaesAP2_1和FaesAP2_2属AP2/ERF家族中euAP2进化系中的AP2型转录因子。表达模式分析表明：FaesAG仅在甜荞thrum型和pin型花植株雌、雄蕊中表达，表达量在2种花雄蕊花药迅速膨大期最高；FaesAP1基因的主要在花器官中表达，在花被片的表达量最高，并在花被片快速生长期维持较高的水平；FaesAP2_1和FaesAP2_2基因与AP2基因的表达模式有很大差别。功能分析表明：FaesAG基因具有参与调控甜荞thrum型和pin型花雌、雄蕊的发育，同时作为甜荞C功能基因，其将A功能基因活性限制在花被轮；FaesAP1是甜荞A功能候选基因，其具有参与调控正常花被片的发育，抑制C功能基因在花被轮的活性。FaesAP1协同FaesAG基因参与促进甜荞花分生组织形成，维持花器官的正常发育。该研究结果对完善目前甜荞雌、雄蕊异型分化理论、花型调控分子基础的同时，为研究荞麦属植物的花型演变积累了资料。受项目资助目前公开发表学术论文5篇，授权发明专利2项，培养毕业硕士2人。