薄壳型苦荞“库-源”关系与种子形成的调控机制研究

Tartary buckwheat contains high amounts of flavonoids compounds, specifically rutin, which provides many health benefits to humans such as the improvement of plasma cholesterol, hypertension and diabetes. However, the low productivity, combined with the thick-shell that is difficult to process, hinders the development of the tartary buckwheat industry. Our research team engaged in the thin-shell type buckwheat germplasm identification and high-yield hybrid breeding for years. We have obtained a number of new high-yield thin-shell tartary buckwheat materials with steady genetic characteristic. Till now, the metabolic physiological characteristics of thin-shell tartary buckwheat and the mechanisms that regulate seed morphogenesis are not clear. Therefore, in this project, the characteristics of carbon and nitrogen metabolism, the patterns of metabolites accumulation, distribution and mobilization, and the traits of yield and quality are investigated to explore the metabolic physiological characteristics that involves in seed development, which is further to reveal the “sink-source” relationship of thin-shell tartary buckwheat. Meanwhile, the microscopic observation of seed and shell, the characteristics of carbon and nitrogen metabolism, the accumulation pattern of metabolites, and the gene cloning, sequencing and expression of AGL11 that involves in the regulation of seed and shell morphogenesis, are investigated to explore the mechanism of the morphogenesis of seed (“sink”) and its shell in thin-shell tartary buckwheat. The proposed work in this project will provide the basis for the research of hybrid breeding, cultivation, promotion, nourishing and hygienical function of thin-shell tartary buckwheat, which is further to promote the industry development of tartary buckwheat.

苦荞富含黄酮类化合物，特别是芦丁，具有降血糖、降血压和降血脂等保健疗效。但是，苦荞的产量水平较低，且果壳厚，在加工过程中难以脱壳，限制了苦荞产业的发展。本研究团队长期从事薄壳型易脱壳苦荞种质资源鉴定与高产杂交育种工作，现已获得一批遗传稳定且具有高产潜力的薄壳苦荞材料。不过，对于薄壳苦荞类型代谢生理特性与种子形成的关系及其调控机制还不清楚。本项目拟对薄壳苦荞进行碳氮代谢生理特性、代谢物质积累、分配与再分配规律、产量与品质性状等研究，探讨薄壳苦荞的代谢生理特性及其与种子形成的关系，揭示薄壳苦荞的“库-源”关系；同时，对种子及其果壳进行解剖学观察、碳氮代谢生理特性、代谢物组分积累规律、调控种子形成关键基因AGL11的克隆、测序、序列分析和基因表达等研究，探讨薄壳苦荞种子(“库”器官)及其果壳形成的机制，为推动薄壳苦荞高产优质杂交育种、栽培、推广、营养保健功能研究与产业发展奠定基础。

常规苦荞果壳厚，难脱壳，限制了产业的发展。本课题组通过有性杂交获得了易脱壳薄壳苦荞品种。本项目以薄壳苦荞贵米苦荞18（M18）、贵米苦荞55（M55）、贵米苦荞104（M105）等为材料，母本小米荞（XMQ）与厚壳父本晋荞麦2号（JQ2）为对照开展研究。显微观察发现灌浆初期薄壳与厚壳种子果壳细胞结构明显差异，表现在细胞壁较薄，细胞层数少、木质化程度低。M18果壳率显著降低，但千粒重也显著低于JQ2，说明薄壳苦荞千粒重还有待改良。对苦荞AGL11进行克隆，发现其编码区全长为678bp。薄壳与厚壳苦荞AGL11序列差异明显，薄壳的M18、M104、M55、翅米荞独立于JQ2，被聚在一起。AGL11基因在根、茎、叶、花、种子中均有表达，但在种子中高表达。灌浆前期和中期JQ2种子中AGL11表达量均显著高于M18和XMQ，表明AGL11基因表达量与种子果壳厚度密切相关。灌浆期对净光合速率，碳、氮代谢关键酶活性和代谢物含量进行研究，发现M18净光合速率较XMQ明显提高，部分淀粉合成相关酶活性和硝酸还原酶活性提高，进而促进籽粒产量提高。M18单株粒数较亲本显著增加，“库”容量明显提高，但饱满粒数无差异，说明“源”不足仍是限制产量提高的主因。GC-MS鉴定到92个代谢物，包括29个有机酸、24个氨基酸、10个糖类物质、6个磷酸盐、6个糖醇类等。灌浆前期、中期和后期，M18与XMQ分别存在60、54和50个显著差异代谢物(DEMs)，与JQ2分别存在65、43和59个DEMs。Venn鉴定到共同差异物分别为33、17和28个。KEGG发现这些DEMs主要富集于氨基酸代谢途径。灌浆期间大多数氨基酸变化趋势与同一代谢途径中其他代谢物相似。灌浆后期苦荞种子中谷氨酰胺含量显著下降，天冬酰胺含量均显著提高，与其它作物不一致。蒸煮食味品质分析发现，M18冷胶粘度显著低于JQ2，回复值显著低于JQ2，食味鉴定分析认为M18口感优于JQ2，推测这可能与显著提高的糖类与糖醇类物质有关。此外，M18种子总黄酮含量达到JQ2的水平，说明其保健功效较好。综合认为薄壳苦荞米适合亚洲人群消费，具有广阔的市场前景。