Starch is major storage substance and accounts for 80% of dry weight in rice endosperm. The rice grain quality is partial determined by component, content and granule structure of starch. In this study, starchy mutant designated flo7, selected from the progeny of tissue culture of Nipponbare, displayed floury and opaque endosperm. The grain length of flo7 was longer, but grain width, grain thickness and 1000grain weight were lower than those of its wild type. Compared with the wild type, the flo7 endosperm accumulated a higher level of glucose, fructose and sucrose, but lower level of dry weight. There was no significant difference in protein content between the wild type and flo7 mutant. The amylose content and gel consistency of flo7 were lower than that of wild type, but the alkali spreading value of flo7 was higher. Scanning electron microscopic examinations showed that the mutant endosperms contained irregular, loosely packed, compound starch granules. Genetic analysis indicated that the mutant phenotype was determined by a single recessive nuclear gene. By means of molecular marker technique, flo7 gene was narrowed down to a 95.1 kb interval which includes 13 open reading frames (ORFs) on the long arm of chromosome 12. The results of RTPCR indicated that the expression levels of some genes involved in starch synthesis were influenced in flo7 mutant. These results suggested that FLO7 plays an important role in the synthesis and regulation of starch in rice.
\[1\]Hirose T,Terao T. A comprehensive expression analysis of the starch synthase gene family in rice (Oryza sativa L.). Planta, 2004, 220(1): 916.
\[2\]Kawasaki T, Mizuno K, Baba T, et al. Molecular analysis of the gene encoding a rice starch branching enzyme. Mol Gen Genet, 1993, 237(1/2): 1016.
\[3\]Kawagoe Y, Kubo A, Satoh H, et al. Roles of isoamylase and ADPglucose pyrophosphorylase in starch granule synthesis in rice endosperm. Plant J, 2005,42(2): 164174.
\[4\]Woo M O, Ham T H, Ji H S, et al. Inactivation of the UGPase1 gene causes genic male sterility and endosperm chalkiness in rice (Oryza sativa L.). Plant J, 2008, 54(2): 190204.
\[5\]Hanashiro I, Itoh K, Kuratomi Y, et al. Granulebound starch synthase I is responsible for biosynthesis of extralong unit chains of amylopectin in rice. Plant Cell Physiol, 2008, 49(6): 925933.
\[6\]Myers A M, Morell M K, James M G, et al. Recent progress toward understanding biosynthesis of the amylopectin crystal. Plant Physiol, 2000, 122(4): 989998.
\[7\]Shimada H, Tada Y, Kawasaki T, et al. Antisense regulation of the rice waxy gene expression using a PCRamplified fragment of the rice genome reduces the amylose content in grain starch. Theor Appl Gene, 1993, 86(6): 665672.
\[8\]Gao M, Fisher D K, Kim K N, et al. Evolutionary conservation and expression patterns of maize starch branching enzyme I and IIb genes suggests isoform specialization. Plant Mol Biol, 1996, 30(6): 12231232.
\[9\]Hamada S, Nozaki K, Ito H, et al. Two starchbranchingenzyme isoforms occur in different fractions of developing seeds of kidney bean. Biochem J, 2001, 359: 2334.
\[10\]Nishi A, Nakamura Y, Tanaka N, et al. Biochemical and genetic analysis of the effects of AmyloseExtender mutation in rice endosperm. Plant Physiol, 2001, 127(2): 459472.
\[11\]Fu F F, Xue H W. Coexpression analysis identifies Rice Starch Regulator1, a rice AP2/EREBP family transcription factor, as a novel rice starch biosynthesis regulator. Plant Physiol, 2010, 154(2): 927938.
\[12\]Wang J C, Xu H, Zhu Y, et al. OsbZIP58, a basic leucine zipper transcription factor, regulates starch biosynthesis in rice endosperm. J Exp Bot, 2013, 64(11): 34533466.
\[13\]Satoh H, Omura T. New endosperm mutations induced by chemical mutagens in rice Oryza sativa L. Jpn J Breeding, 1981, 31(3): 316326.
\[14\]She K C, Kusano H, Koizumi K, et al. A novel factor FLOURY ENDOSPERM2 is involved in regulation of rice grain size and starch quality. Plant Cell, 2010, 22(10): 32803294.
\[15\]Nishio T, Iida S. Mutants having a low content of 16kDa allergenic protein in rice (Oryza sativa L.). Theor Appl Genet, 1993, 86(2/3): 317321.
\[16\]Kang H G, Park S, Matsuoka M, et al. Whitecore endosperm floury endosperm 4 in rice is generated by knockout mutations in the C4type pyruvate orthophosphate dikinase gene (OsPPDKB). Plant J, 2005, 42(6): 901911.
\[17\]Ryoo N, Yu C, Park C S, et al. Knockout of a starch synthase gene OsSSIIIa/Flo5 causes whitecore floury endosperm in rice (Oryza sativa L.). Plant Cell Rep, 2007, 26(7): 10831095.
\[18\]Fujita N, Yoshida M, Kondo T, et al. Characterization of SSⅢadeficient mutants of rice: The function of SSⅢa and pleiotropic effects by SSⅢa deficiency in the rice endosperm. Plant Physiol, 2007, 144(4): 20092023.
\[19\]Cheng P, Wang Y H, Liu Feng, et al. FLOURY ENDOSPERM6 encodes a CBM48 domaincontaining protein involved in compound granule formation and starch synthesis in rice endosperm. Plant J, 2014, 77(6): 917930.
\[20\]Steegmans M, Iliaens S, Hoebregs H, et al. Enzymatic, spectrophotometric determination of glucose, fructose, sucrose, and inulin/oligofructose in foods. J AOAC Int, 2004. 87(5): 12001207.
\[21\]中华人民共和国农业行业标准.米质测定方法NY14788. 北京： 中国标准出版社, 2002.
\[22\]孙成效, 段彬伍, 谢黎虹,等. 利用近红外透射光谱技术同步测定糙米的多项品质指标初报. 中国水稻科学, 2006, 20(4): 451454.
\[23\]康海岐, 常红叶. 杂交水稻主要亲本材料的垩白性状及其胚乳结构电镜扫描. 中国农学通报, 2007, 23(4): 180185.
\[24\]Wu K S, Tanksley S D. Abundance, polymorphism and genetic mapping of microsatellites in rice. Mol Gen Genet, 1993, 241(1/2): 225235.
\[25\]Li Z, Trick H N. Rapid method for highquality RNA isolation from seed endosperm containing high levels of starch. BioTechniques, 2005, 38(6): 872876.
\[26\]金田蕴, 李辉. 水稻稳定高垩白率突变体的获得与理化特性分析.作物学报, 2010,6(1):121132.
\[27\]姚东升, 宋任涛. 玉米粉质胚乳突变体的研究进展. 自然杂志, 2013, 35(2): 105111.
\[28\]Wang Y, Ren Y, Liu X, et al. OsRab5a regulates endomembrane organization and storage protein trafficking in rice endosperm cells. Plant J, 2010, 64(5): 812824.
\[29\]Liu F, Ren Y, Wang Y, et al. OsVPS9A functions cooperatively with OsRAB5A to regulate postGolgi dense vesiclemediated storage protein trafficking to the protein storage vacuole in rice endosperm cells. Mol Plant, 2013, 6: 19181932.
\[30\]Ren Y, Wang Y, Liu F, et al. GLUTELIN PRECURSOR ACCUMULATION3 encodes a regulator of postGolgi vesicular traffic essential for vacuolar protein sorting in rice endosperm. Plant Cell, 2014, 26(1): 410425.
\[31\]Chavrier P, Goud B. The role of ARF and Rab GTPases in membrane transport. Curr Opin Cell Biol, 1999, 11(4): 466475.
\[32\]HanzalBayer M, Renault L, Roversi P, et al. The complex of Arl2GTP and PDEσ: From structure to function. EMBO J, 2002, 21(9): 20952106.
\[33\]Fukuda M, Wen L, SatohCruz M, et al. A guanine nucleotide exchange factor for Rab5 proteins is essential for intracellular transport of the proglutelin from the Golgi apparatus to the protein storage vacuole in rice endosperm. Plant Physiol, 2013, 162(2): 663674.
