水稻杂交后代灌浆成熟期籽粒淀粉合成关键酶和谷氨酰胺合成酶活性变化的初步研究

 以东农423和藤系180为试材,籽粒直链淀粉和蛋白质含量为选择指标,通过逐代的定向选择形成了遗传背景相近且直链淀粉和蛋白质含量有显著差异的杂种后代,并对水稻灌浆成熟过程中籽粒ADPG焦磷酸化酶、可溶性淀粉合酶、淀粉分支酶、谷氨酰胺合成酶活性变化进行了初步研究。高直链淀粉含量杂交后代的籽粒ADPG焦磷酸化酶、可溶性淀粉合酶、淀粉分支酶活性峰值显著或极显著高于低直链淀粉含量后代,而且在籽粒灌浆前期蛋白质含量高的后代籽粒谷氨酰胺合成酶活性显著或极显著高于蛋白质含量低的后代。因此,通过直链淀粉和蛋白质含量的连续定向选择可以显著提高或降低灌浆过程中的籽粒碳氮代谢关键酶活性。     

控释氮肥对杂交水稻糙米蛋白质品质和氮代谢关键酶活性的影响

以八两优100（杂交早稻）和威优46（杂交晚稻）为材料,研究了施用控释氮肥对稻米蛋白质含量、氨基酸含量及其组分以及叶片和籽粒中硝酸还原酶（NRase）、谷氨酰胺合成酶（GS）和蛋白水解酶活性的影响。结果表明,八两优100和威优46控释氮肥处理糙米蛋白质、复合蛋白含量均显著或极显著高于尿素处理,其中谷蛋白和谷蛋白/醇溶蛋白比值增幅明显。施控释氮肥的八两优100和威优46糙米氨基酸总量、必需氨基酸和限制性氨基酸含量均较施用尿素的明显提高。在施用尿素和控释氮肥条件下,供试两组合叶片中NRase、蛋白水解酶、GS以及籽粒中的GS活性的动态变化一致。施用控释氮肥有利于功能叶中NRase、GS、蛋白水解酶以及籽粒中的GS活性维持较高水平。控释氮肥对杂交水稻功能叶氮代谢关键酶活性和籽粒中蛋白质合成及氨基酸积累均有明显的调节作用。这可能是控释氮肥能显著提高杂交水稻产量和蛋白质及氨基酸含量的生理原因之一。     

水稻灌浆成熟期籽粒谷氨酰胺合成酶活性变化及其与稻米品质关系的初步研究

 选用稻米蒸煮食味品质有显著差异的4个粳稻品种，通过盆栽试验对水稻灌浆成熟期籽粒谷氨酰胺合成酶活性变化及其与稻米蒸煮食味品质关系进行了初步研究。结果表明，水稻灌浆过程中籽粒谷氨酰胺合成酶活性随灌浆进程逐渐增加，达到峰值后又逐渐下降，呈单峰曲线变化；抽穗15 d以前蛋白质含量高的品种谷氨酰胺合成酶活性大于蛋白质含量低的品种，而以后与之相反；灌浆前期，籽粒谷氨酰胺合成酶活性与味度值、最高黏度、崩解值间呈负相关，灌浆中、后期呈正相关，而与籽粒最终蛋白质含量和黏滞峰消减值在灌浆前期呈正相关，灌浆中、后期呈负相关，而且相关程度随灌浆时段而发生变化；抽穗后15~20 d是籽粒谷氨酰胺合成酶活性与味度值、RVA谱特性间的相关性质发生变化的转折时期。     

粳稻超亲变异系籽粒谷氨酰胺合成酶基因表达特性及序列变异分析

选用籽粒蛋白质含量有显著差异的亲本和杂种后代超亲变异系,比较分析灌浆过程中籽粒蛋白质积累特性、谷氨酰胺合成酶(GS)活性变化、GS基因mRNA表达量变化和基因碱基序列。结果表明,杂交后代通过籽粒蛋白质含量的连续定向选可获得超亲变异系,籽粒蛋白质积累量与基因型紧密相关;灌浆过程中籽粒GS活性呈单峰曲线变化,籽粒蛋白质含量与籽粒GS活性密切相关,而且籽粒GS活性也能产生超亲变异;在灌浆过程中籽粒蛋白质含量不同的亲本及超亲变异系籽粒GS1.3和GS2基因的mRNA表达量变化趋势基本一致,即随灌浆进程mRNA表达量逐渐增加,到抽穗后15~20d表达量最高,随后逐渐下降,呈单峰曲线变化;GS1.3和GS2基因mRNA表达量与籽粒蛋白质含量关系密切,GS基因mRNA表达量高的基因型籽粒蛋白质含量也高,而且超亲表达;尽管不同品种GS1.3和GS2基因碱基序列保守性很高,但不同品种水稻GS1.3和GS2基因的碱基序列和蛋白质氨基酸序列并不完全一致,存在着个别碱基不同的基因多态性,品种间有性杂交后代在基因分离和稳定过程中通过碱基的替换仍然能发生碱基的随机性变化及三联体密码和氨基酸的变化。     

6-苄氨基嘌呤对水稻灌浆成熟期籽粒氮代谢及蒸煮食味品质的影响

选用两个品质不同的粳稻品种,研究在抽穗期喷洒6 苄氨基嘌呤（6 BA）对灌浆成熟期籽粒氮代谢及蒸煮食味品质的影响。 抽穗后随灌浆进程籽粒谷氨酰胺合成酶活性逐渐增加,达到峰值后又逐渐下降,呈单峰曲线变化,且抽穗后20 d 的酶活性最高;蛋白质含量高的品种灌浆前期籽粒谷氨酰胺合成酶活性高于蛋白质含量低的品种;与未喷6 BA对照相比,抽穗期喷洒6 BA供试品种的味度值、最高黏度、崩解值、可溶性蛋白含量等均有不同程度的提高,籽粒谷氨酰胺合成酶活性和消减值降低,但蛋白质和直链淀粉含量变化很小。     

烯效唑对水稻氮代谢及稻米蛋白质含量的影响

以杂交稻组合汕优63为材料,探讨了烯效唑处理对水稻开花后剑叶和籽粒氮代谢、稻米蛋白质含量及产量的影响。结果表明,烯效唑处理后,籽粒灌浆前、中期剑叶内可溶性蛋白质含量提高,而成熟期其含量与对照基本相同,甚至略低于对照;烯效唑提高了强、弱势粒中谷氨酰胺合成酶活性以及强势粒发育前期的非蛋白氮含量,并促进其向蛋白氮的转化,使成熟期非蛋白氮含量低于对照,而各时期蛋白氮含量均高于对照,成熟期强、弱势粒中蛋白氮含量和单粒蛋白氮绝对积累量均得以提高;烯效唑提高了稻米内蛋白质含量和蛋白质产量,浸种和喷施处理蛋白质含量平均分别比对照高7.2%和8.3%,蛋白质产量平均分别比对照高13.1%和13.4%。     

高温对水稻灌浆期籽粒氮代谢关键酶活性及蛋白质含量的影响

 选用粳稻品种越光与籼稻品种IR72为材料,研究了高温对水稻灌浆期籽粒谷氨酰胺合成酶（GS）、谷氨酸合酶（GOGAT）、谷氨酸 草酰乙酸转氨酶（GOT）、谷氨酸 丙酮酸转氨酶（GPT）的活性及蛋白质与氨基酸含量的影响。结果表明,灌浆期高温下水稻籽粒GOGAT、GOT与GPT活性显著或极显著升高,但籽粒GS活性显著或极显著降低;籽粒蛋白质及氨基酸各组分含量极显著增加。高温下籽粒GS活性显著降低并未影响籽粒蛋白质的合成,认为籽粒GS不是限制水稻蛋白质合成的关键酶。     

粳稻杂种后代胚乳可溶性淀粉合成酶及同工型基因表达特性分析

以籽粒直链淀粉含量为选择指标,从东农423×藤系180F2代起连续定向选择培育成的籽粒直链淀粉含量有显著差异的F10后代东农1006(直链淀粉含量为18.82%)、东农1012(直链淀粉含量为7.70%),同样,从系选1号×通769后代中选出东农1001(直链淀粉含量为17.51%)、东农1024(直链淀粉含量为7.40%)比较分析了灌浆过程中籽粒直链淀粉含量和可溶性淀粉合成酶活性及同工型基因表达量等变化特征。结果表明,灌浆不同时期籽粒直链淀粉含量低的后代及亲本直链淀粉量始终低于直链淀粉含量高的后代及亲本;成熟期籽粒直链淀粉含量低的亲本和后代籽粒支链淀粉含量均显著高于籽粒直链淀粉含量高的亲本和后代,抽穗后10d、17d、24d的籽粒直链淀粉含量与支链淀粉含量间均呈负相关,但相关未达显著水平;抽穗后10d、17d、24d的可溶性淀粉合成酶活性与籽粒直链淀粉含量的相关系数分别为0.8115**,-0.7554*,-0.5957,与支链淀粉含量的相关系数分别为-0.0694,0.5453,-0.0207;在灌浆过程中亲本及后代的胚乳OsSSSⅠ、OsSSSⅡ-1、OsSSSⅡ-3、OsSSSⅢ-1和OsSSSⅢ-2基因随籽粒灌浆进程其mRNA转录表达量逐渐增加,达到峰值后又逐渐下降,呈单峰曲线变化;而OsSSSⅢ-2和OsSSSⅣ-2基因mRNA转录表达量在灌浆各时期都比其他基因大;灌浆不同时期直链淀粉含量高的后代与高亲相比、直链淀粉含量低的后代与低亲相比,既有转录表达量增加的基因,也有降低的基因;可溶性淀粉合成酶活性与OsSSSⅠ、OsSSSⅡ-3、OsSSSⅢ-2的mRNA转录表达量正相关,相关达显著水平;与OsSSSⅡ-1、OsSSSⅣ-2的mRNA转录表达量正相关,但相关未达显著水平,与OsSSSⅢ-1的mRNA转录表达量呈负相关,但相关未达显著水平。     

不同蛋白含量大豆品种氮代谢关键酶活性及叶片氮同化物含量变化

以高蛋白野生大豆、普通野生大豆和栽培大豆为材料,研究大豆籽粒蛋白质含量与各生育期叶片谷氨酰胺合成酶活性(GSA)、硝酸还原酶活性(NRA)以及叶片不同氮同化物含量之间的关系。结果表明:高蛋白野生大豆在V6期到R8期的NRA、R3期开始各个时期的GSA都明显高于其它品种。R3期以外的其它各生育期,高蛋白野生大豆可溶性蛋白含量高于其它品种。叶片游离氨基酸含量则表现为R2期之前野生大豆高于栽培大豆,R2期及以后各个时期又明显低于栽培大豆。籽粒蛋白质含量与R3期到R8期的NRA以及R3、R8期的GSA呈正相关关系。V3期可溶性蛋白质含量和V6期游离氨基酸含量与籽粒蛋白质含量呈正相关。叶片硝态氮含量与籽粒蛋白质含量没有相关性。     

大豆不同亲本组合对后代品系蛋白质含量的影响

结合大豆育种实际工作,设置低蛋白×低蛋白、低蛋白×高蛋白2种不同类型的大豆杂交组合,先后对各组合类型后代单株及后代品系蛋白质、油分含量进行测定分析。结果表明,大豆杂交亲本蛋白质含量通过杂交后代群体对后代品系蛋白质含量特征有显著的影响,亲本蛋白质含量与后代品系蛋白质含量表现为显著的正相关。不同蛋白质含量的大豆杂交亲本组合类型对后代品系蛋白质含量有显著的影响。试验明确了大豆杂交后代群体蛋白质含量的遗传过程以及选择作用对后代品系蛋白质含量的影响,为大豆蛋白质育种实践提供参考。     

Effects of Grain Protein Content Selection on Protein Content and Key Enzyme Activity Involved in Nitrogen Metabolism in Progenies Derived from a Rice Cross

Two japonica rice parents (Tong 769 and Xixuan 1) and their progenies, significantly different in protein content of grains, were investigated to reveal the activities of proteinase in leaves and glutamine synthetase in grains, as well as the dynamic changes of soluble protein content in grains during rice grain filling. The results showed that the parents were very similar in protein content, however, advanced lines with different protein contents in grains and varied activities of proteinase and glutamine synthetase were acquired by consecutively directional selection of the grain protein content in their progenies. Moreover, the enzyme activity and the protein content in grains exceeded their parents during grain filling. The protein content in grains was positively related with the proteinase activity, and the soluble protein content was negatively related with the glutamine synthetase activity in grains to some extent.     

Changes in Activities of Key Enzymes for Starch Synthesis and Glutamine Synthetase in Grains of Progenies from a Rice Cross During Grain Filling

The progenies differed in amylose and protein contents in grains, which derived from a rice cross, Dongnong 423×Toukei 180, were used to study changes in the activities of ADP-glucose pyrophosphorylase (AGPP), soluble starch synthetase (SSS), starch branching enzyme (SBE) and glutamine synthetase (GS) in rice grains during grain filling. The activities of AGPP, SSS and SBE gradually increased and then declined as a single-peak curve with the process of grain filling in the progenies with high and low amylose contents in grains. The progenies with high amylose content peaked earlier in the AGPP, SSS and SBE activities and had higher AGPP, SSS and SBE activities at the early grain filling stage than those with low amylose content. The GS activity peaked earlier and was higher at the late stage of grain filling in the progenies with high protein content than in those with low protein content. It is suggested that the activities of key enzymes for starch synthesis and glutamine synthetase could be changed in oriented breeding for amylose and protein contents in grains.     

Effects of Uniconazole on Nitrogen Metabolism and Grain Protein Content of Rice

The effects of uniconazole by soaking seeds and spraying leaves at booting stage with different concentrations （0, 20 and 40 mg/kg） on the nitrogen metabolism of flag leaf and grains after flowering, and rice grain protein content and yield were studied with hybrid rice combination Shanyou 63. Under uniconazole treatment, the soluble protein content in flag leaf was increased in early and middle period of grain filling, but this content was nearly the same as or even lower than that of control at maturity; Glutamine synthetase activity in superior and inferior grains and non-protein nitrogen content in superior grains at early stage of grain development were promoted, and moreover, the transforming speed from non-protein nitrogen to protein nitrogen was accelerated; Non-protein nitrogen content was lower than that of control at maturity, but protein nitrogen content at each stage was higher than those of control; Protein nitrogen content in superior and inferior grains and protein nitrogen absolutely accumulative content in a grain both were enhanced and protein content and yield in rice grain were raised. The application of uniconazole by soaking seeds and spraying leaves raised crude protein content by an average of 7.2% and 8.3%, and protein yield by an average of 13.1% and 13.4%, respectively.     

Changes in Activities of Glutamine Synthetase during Grain Filling and Their Relation to Rice Quality

Four japonica rice varieties differed in cooking and eating qualities were used in a pot experiment to study the relationship between the activities of glutamine synthetase during grain filling and rice quality. The activities of glutamine synthetase gradually increased and then declined as a single peak curve in the course of grain filling. The 15th day after heading was a turning point, before which the enzymatic activities in the inferior rice varieties with high protein content were higher than those in the superior rice varietie with low protein content, and after which it was converse. The activity of glutamine synthetase in grain was correlated with the taste meter value, peak viscosity and breakdown negatively at the early stage of grain filling whereas positively at the middle and late stages. Moreover, it was correlated with the protein content of rice grain and setback positively at the early stage and negatively at the middle and late stages. The correlation degree varied with the course of grain filling. From 15 days to 20 days after heading was a critical stage, in which the direction of correlation between the activity of glutamine synthetase and taste meter value and RVA properties of rice changed.