The Genotypic Difference And Position Distribution Of Rice Seeds During Quality Formation

The "sink-source-stream" during grain filling, mainly about carbon-nitrogen metabolism, were mostly related to rice quality. In carbon metabolism, the assimilates transported from leaves and stems (source) to storage organs(sink), and reserve starch is eventually biosynthesized in amyloplasts afterward. For plants, inorganic nitrogen in the soil in the form of nitrate and ammonia is initially converted into glutamine and glutamate, thereby synthesized protein and deposited in protein body.In this paper, three cultivars differing in grain quality were used to investigate the expression pattern of various SSS isoform genes in filing stage and its relationship to starch quality in rice grain, and differences in starch physicochemical, physiological characteristics and the expression of gene related to starch synthesis were determined between Zhonghual1and Su-11; the morphology character within a panicle and the effect of protein on rice quality were also studied. The main results were as follows:1. The SSS activities of the three cultivars during the guain filling stage had no significant difference, while the GBSS activity for Zaoxiangnuo was obviously lower than that of Zhe104and Zhe733. Among the8isoforms, SSS, SSSⅠ, SSSⅡa and SSSⅢa had a higher expression in rice endosperm than in other organs, such as root, stem. The expression of the main isoforms of SSS and GBSS during grain filling stage indicated that they were difference in cultivars and grain filling stages.2. The marked difference in the shapes and sizes of starch granule and other starch physicochemical properties were observed beween Su-11mutant and its CK, with the mutant Su-11having relatively lower AC, much higher sucrose and fructose compared to wild-type. Although the activities of ADPG, SSS, SBE between the two cultivars showed the similar trend During the grain filling stage, while there was a significant difference in R enzyme acitivity, for the same period of the filling stage, the R enzyme activity of Su-11mutant was much lower.3. The differential expression was examined in starch synthesis genes between Zhonghua11and the mutant Su-11. Compared to Zhonghua11, the isoforms of SBE in Su-11were up-regulated in the14th and21th days after grain filling stage.For the two cultivars,IDBEⅢ and RBE were the main DBE expressed isoforms, for each of the two isoforms they got the similar trend between the two cultivars.4. The44rice cultivars amylose content ranged from14.8%to21.4%, with a mean of17.8%. Morphological traits of the rice panicle were poorly associated with mean grain AC on the average of the whole panicle, but closely related to AC variation and spatial distribution within a panicle, The extent of AC differences among the rachides within a panicle were also cultivar dependent, and significant differences were found between middle and top rachides for the compact-panicle cultivars, and between middle and bottom rachides for the loose-panicle cultivars.5. The marked difference in the anatomical structure of the vascular bundle was found between different positional rice rachillae, with the relative large total vascular area, phloem area and vessel area in central vascular bundle for superior positional rachilla within a panicle, indicting that the superior rachilla had better structure for the assimilate transport compared to the inferior positional rachilla; the similar time-course in the degradation pattern of some organelles of SE and CC in central vascular phloem was observed in different positional rachillae at grain filling stage, with the relative delaying degradation and disintegration of SE,CC and phloem parenchyma cells for inferior positional rachilla; the abundant mitochondrion, chloroplast, starch granules and plasmodesmata, and numerous CaM labeling density were found in SE and CC of superior rachilla compared to inferior positional rachilla at beginning filling stage, while no significant differences between two types of rachilla at middle and late filling stages, implying that superior postional rachilla had relatively better transporting function at initial filling stage relative to inferior rachilla.6. The effects of high temperature after flowing period on GOT and GPT activity showed the similar trend,increasing at early grain filling stage and decreasing at late grain filling stage,the activity of GS under high temperature were generally higher than that of under control temperature in the same period. The composition and accumulation configuration of storage protein in rice grain changed with the high temperature.