Journal Article

Expression Patterns of Genes Encoding Carbohydrate-metabolizing Enzymes and their Relationship to Grain Filling in Rice (<i>Oryza sativa</i> L.): Comparison of Caryopses Located at Different Positions in a Panicle

Tsutomu Ishimaru, Tatsuro Hirose, Toshiaki Matsuda, Akitoshi Goto, Kazunari Takahashi, Haruto Sasaki, Tomio Terao, Ryu-ichi Ishii, Ryu Ohsugi and Tohru Yamagishi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 4, pages 620-628
Published in print April 2005 | ISSN: 0032-0781
Published online April 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci066
Expression Patterns of Genes Encoding Carbohydrate-metabolizing Enzymes and their Relationship to Grain Filling in Rice (Oryza sativa L.): Comparison of Caryopses Located at Different Positions in a Panicle

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In rice, caryopses located at the base of the panicle have a lower growth rate than those at the tip of the panicle. The former and latter types of caryopses are called inferior and superior caryopses, respectively. Taking the different growth rate into consideration, sugar status and the expression of genes encoding carbohydrate-metabolizing enzymes in inferior caryopses were compared with those in superior caryopses. During the first 5 d after flowering, superior caryopses elongated rapidly, but inferior caryopses did not. At this phase, inferior caryopses had a low ratio of hexose to sucrose, high activity of acid invertase and the absence of the expression of the genes encoding the above enzymes except for two isoforms of cell wall invertase, OsCIN4 and INV1, in comparison with superior caryopses. At the start of caryopsis elongation in both superior and inferior caryopses, the hexose/sucrose ratio increased accompanied by gene expression of vacuolar invertase (INV3), sucrose synthase (RSus1) and ADP-glucose pyrophosphorylase (AGP-L2: D50317). Furthermore, the genes related to endospermal starch accumulation were expressed highly with the decrease in the hexose/sucrose ratio after its peak. Based on the comparison of superior and inferior caryopses, the possible mechanism of grain filling in rice is discussed.

Keywords: Carbohydrate metabolism; Grain filling; Inferior caryopses; Oryza sativa L.; Sink strength; Superior caryopses; AGPase, ADP-glucose pyrophosphorylase; CWI, cell wall invertase; DAF, days after flowering; DIG, digoxigenin; SUS, sucrose synthase; VCI, vacuolar invertase.

Journal Article.  5989 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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