| 90% of composition of the rice in our daily diet is starch. The content of amylose and the elaborate construction of amylepctin both play a pivotal role in improving the cooking and eating quality properties of rice. The research on accumulation patterns and genetic mechanism of the synthesis of amylose,starch and amylepctin might help building the theoretical foundation for reaching the quality-improving target, The grain filling period is the most important period for starch accumulation, also the most actived time for the enzymes which belongs to the complex system related to starch synthesis, including AGPase, SS, SBE and DBE. ISA acts a crucial role of DBE catalyzing the hydrolysis(debranch) of α-(1–6) bonds in amylopectin and removal of the improper branch in order to product the correct amylopectin.In this study, the two transgressive lines which have higher amylose accumulation than their parents, and waxy rice, Longdao 8 were chosed as material. By analyzing the starch composition, ISA activity and key starch synthesis genes expression pattern in different grain filling period, we attempted to reveal the amylose accumulation difference in endosperm and the genetic reason for it; by unveiling how ISA influence the starch composition, we might help to uncover the mechanism of the transgressive variety of amylose content quantity. The nitrogenous fertilizing experiment was designed to know the how the composition of grain fertilizer affect the key genes expression of starch synthesis, in order to unveil the response of rice starch for the nitrogenous.The result shows that the first 20 days of grain filling are essential for the starch accumulation, in which the total content of starch reaches 90% of the maturity, suggesting it is important to focus on the agricultural manage at the early stage of grain tiling. The amylose, amylopectin and starch showed ‘s’ accumulation trend in japonica rice but the waxy rice has higher accumulation rate than japonica rice. In addition, amylose accumulation in endosperm is mainly regulated by the genetic level, as the high AC line always show higher amylose content than the low AC line at the same stage.Enzyme activity of ISA shows a unimodal curve trend model in endosperm of japonica rice;mediem level at 10 th – peak at 15 th – half down at 20 th – low at 25 th and30th,which hasnegative association with the amylose accumulation while positive with amylopectin accumulation. However, the waxy rice shows linear accumulation of ISA having the positive association with starch composition accumulation, suggesting that there is difference in the starch synthesis between japonica and waxy rice and ISA has greater impact in the starch synthesis of waxy rice.During grain filling period, ISA1 expression has the same pattern showing they have positive association; ISA2 was expressed highly at early stage but decreased quickly at later stage; ISA3 expression increased slightly at the middle and later stage, suggesting ISA1 might be the major gene controlling the enzyme activity of ISA. In the medium term of grain filling, the rice having high ISA1 expression showed low AC accumulation. GBSS1 has different expression pattern between high AC and low AC rice: in high AC rice, GBSS1 was expressed higher level at later stage, but in low AC rice, GBSS1 was expressed higher at middle stage.Rising the ratio of spike N-fertilizer can change the gene expression of GBSS1 and ISAs in different way,more obviously in early stage rather than later of grain filling period.At 10 th after heading,the gene expression of ISA1 and ISA2 increases,while ISA3 decreases,and GBSS1 doesn’t show serious change;At 20 th GBSS1 increases,while ISAs don’t change any more. |
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