Abstract:

【Objective】The research aims to lay a theoretical basis for clarifying the influencing mechanism of nitrogen fertilization during grain filling period on rice starch quality.【Method】Four japonica rice varieties with significant difference in amylose content in grains were selected. Pot experiments were conducted to study the effect of nitrogen application on the starch component and protein content in rice grains, and the protein hydrolysis of rice grains on starch viscosity properties, and to analyze the effect of nitrogen nutrition on the activity of sucrose synthase(SuSy), sucrose phosphate synthase(SPS) and acid invertase(AI) and the mRNA expression levels of OsGBSSⅠ, OsISAⅠ, OsSBEⅠand OsSBEⅡ genes of rice grains during grain filling period.【Results】The results showed that the grain amylopectin content was sensitive to nitrogen nutrition, and nitrogen nutrition during grain filling period changed the content of starch components in grains. The cooking and eating quality of high amylose content varieties degraded even more. The removal of rice protein could significantly improve the viscosity of rice, and the starch composition had a great influence on the viscosity properties of rice starch. Increasing nitrogen nutrition at grain filling stage significantly or highly significantly increased the activity of SuSy and AI in grains, and significantly inhibits the activity of SPS. The nitrogen nutrition at grain filling stage changed the mRNA expression level of OsGBSSⅠ, OsISAⅠ and OsSBEⅡ of rice grains at different stages of grain filling, so that the change dynamics of the mRNA expression quantity of these genes changed during grain filling period except OsSBEⅠ. Due to the influence of nitrogen nutrition, at the beginning of grain filling, OsGBSSⅠ expression level was upregulated significantly, but downregulated significantly in the middle and late stages of grain filling. Nitrogen fertilization could significantly inhibit the transcription expression quantity of OsISAⅠ of grains at grain filling stage and OsSBEⅠ of grains in the middle and late stages of grain filling, and could significantly improve the mRNA expression quantity of OsSBEⅠ of grains in the early and middle stages of grain filling. Nitrogen nutrition could inhibit the transcription expression quantity of OsSBEⅡ gene of grains at the beginning of grain filling, and improve the transcription expression quantity of genes in the middle and late stages of grain filling.【Conclusion】In addition to the effect of protein content on starch quality during grain filling and ripening, nitrogen nutrition also affected starch content and fine structure by regulating enzyme activities and gene expression related to starch synthesis. Ultimately, it changed the rice viscosity and taste quality.

Key words: rice, nitrogen nutrition, key enzyme genes involved in starch synthesis, transcription expression quantity

摘要：

【目的】旨在为阐明灌浆成熟期氮素营养对水稻淀粉品质影响机理以及建立优质高产水稻栽培技术提供理论依据。【方法】选用4个籽粒直链淀粉含量差异显著的粳稻品种,通过盆栽试验研究氮素营养对稻米淀粉组分和蛋白质含量及稻米蛋白质水解对淀粉黏滞特性的影响,并分析氮素营养对灌浆过程中籽粒蔗糖合酶(SuSy)、蔗糖磷酸合酶(SPS)、蔗糖酸性转化酶(AI)活性及OsGBSSⅠ、OsISAⅠ、OsSBEⅠ、OsSBEⅡ基因转录表达量的影响。【结果】结果表明,籽粒支链淀粉含量对氮素营养很敏感,灌浆成熟期氮素营养能改变籽粒淀粉组分含量;施氮条件下,高直链淀粉含量品种蒸煮食味品质下降更加明显,去除稻米蛋白质可明显提高稻米黏滞特性,蛋白质对淀粉黏滞特性的影响很大;增加灌浆成熟期氮素营养能显著或极显著提高籽粒SuSy和AI活性,显著抑制籽粒SPS活性;灌浆成熟期氮素营养能改变灌浆不同时期籽粒OsGBSSⅠ、OsISAⅠ和OsSBEⅡ基因转录表达量,以致灌浆过程中这些基因的转录表达量变化动态发生改变,但OsSBEⅠ基因转录表达量不因氮素营养而发生改变;受氮素营养的影响,灌浆起始期籽粒OsGBSSⅠ基因表达量明显上调,而灌浆中后期明显下调;氮素营养明显抑制灌浆成熟期籽粒OsISAⅠ基因和灌浆中后期的OsSBEⅠ基因转录表达,显著提高灌浆前期和中期的籽粒OsSBEⅠ基因转录表达量;氮素营养能抑制灌浆起始期籽粒OsSBEⅡ基因的转录表达,而提高灌浆中后期的基因转录表达。【结论】灌浆成熟期氮素营养除了通过蛋白质含量对淀粉品质产生影响外,还通过调控淀粉合成相关的酶活性和基因表达量等生理环节对淀粉含量和精细结构起作用,最终改变稻米黏滞特性和食味品质。

关键词: 水稻, 氮素营养, 淀粉合成关键酶基因, 转录表达量