水稻胚乳5-羟色胺累积的效应及其代谢关联研究

There are a variety of metabolites in rice endosperm, which are closely related to endosperm development, nutritional quality and seed physiology. Serotonin, as an important secondary metabolite, not only affects physiological metabolism in animals and humans, but also involves in plant growth, development, defense and stress response. However, the serotonin accumulation and its metabolic connection with other pathway(s) are barely reported in rice, especially in rice endosperm. In previous studies, we found that the serotonin biosynthesis and accumulation were closely related to lysine metabolism in rice endosperm, and both serotonin and lysine biofortification caused dark-brown seed phenotype. Besides, the serotonin accumulation could be obviously induced by low temperature during seed development. In present study, with the aim to better understand the metabolic connections among nutrients in rice endosperm, high serotonin transgenic rice lines will be used to investigate the effects on physiological and biochemical of seed development, quality formation and seed germination. More importantly, the systems biological approaches, including transcriptome, metabolome and bioinformatics, and the molecular and biochemical technologies such as qRT-RCR and LC/GC-MS will be used to explore the connections between serotonin and other metabolic pathways, such as lysine metabolism. Besides, the response of serotonin metabolism to temperature will be further analyzed by with low temperature treatment during seed development. Taken together, all the experiments and data will greatly strength our understanding of the metabolic connections among different nutrients in rice endosperm, and subsequently help to further improve rice nutritional quality.

水稻胚乳中含有种类丰富的代谢物，与籽粒发育、品质形成及种子生理等密切相关。5-羟色胺作为一种重要的次生代谢物，其不仅影响动物的生理代谢，还参与植物的生长发育和胁迫防御等，但其在水稻籽粒中的累积效应和代谢关联研究还较为欠缺。我们在前期研究中发现，水稻胚乳中5-羟色胺合成与赖氨酸代谢存在显著关联，它们的累积均会引起较为明显的棕褐色籽粒表型，并易受低温诱导。本研究拟以已培育的高5-羟色胺含量转基因水稻为材料，比较分析胚乳中5-羟色胺累积对籽粒发育、品质形成及种子萌发等生理生化的影响。同时，借助代谢组学、转录组学、生物信息学等系统生物学手段和定量PCR、LC/GC-MS等技术，解析5-羟色胺累积后与赖氨酸等其他代谢途径的关联，并结合温度处理探明其在低温胁迫中的作用及其对低温的响应机制。相关结果可望为深入阐明水稻胚乳中各营养元素代谢通路间的关联机制提供理论基础，也可为改良稻米营养品质提供技术指导。

水稻胚乳中含有种类丰富的代谢物，与籽粒发育、品质形成及种子生理等密切相关。5-羟色胺作为一种重要的次生代谢物，参与植物的生长发育和胁迫防御等，但其在水稻籽粒中的累积效应和代谢关联研究还较为欠缺。本研究通过过表达5-羟色胺合成代谢关键基因TDC1、TDC3和T5H，创建高5-羟色胺含量的转基因水稻，进而比较分析各转基因材料及非转基因对照的生长发育、品质形成及种子生理生化特性。结果显示TDC1和TDC3基因过表达材料中色胺、5-羟色胺含量大幅度提高，但对植株的生长发育有较为明显的影响，产生如植株变矮、种子变小、籽粒呈黑色等表型；而T5H基因过表达材料中5-羟色胺含量提高幅度相对适中，且对植株生长发育、种子生理生化和稻米品质等影响较小或没有影响。同时，借助代谢组学、转录组学、生物信息学等系统生物学方法和定量RT-PCR、LC/GC-MS等技术，明确5-羟色胺累积可对氨基酸代谢、次级代谢、激素合成及信号传导、能量代谢等途径产生一定的影响，但转化GT的效应小于GD1和GD3。最后，通过差异代谢物和差异表达基因的关联分析，发现高5-羟色胺水稻中影响较大的代谢途径与高赖氨酸水稻中关联的代谢途径存在高度的重合，说明5-羟色胺与赖氨酸合成代谢之间确实存在关联，且与脂肪酸和激素代谢也存在关联。进一步地，通过对多个高5-羟色胺转基因材料比较分析，发现所有高5-羟色胺水稻中色氨酸代谢途径的最终产物犬尿喹啉酸均显著改变，因此暗示调控色氨酸和赖氨酸代谢途径可能使得下游代谢物发生紊乱，激发了5-羟色胺和赖氨酸代谢的新途径。相关研究可望为高5-羟色胺功能性水稻的培育提供一种可能的策略，可为深入阐明水稻胚乳中氨基酸代谢通路间的关联机制提供理论基础，也可为改良稻米营养品质提供技术指导。