title: Overexpression of a rice TIFY gene increases grain size through enhanced accumulation of carbohydrates in the stem.
abstract: Screening of rice full-length cDNA overexpressing (FOX) lines allowed the identification of a TIFY gene, TIFY11b, as a growth-promoting gene whose overexpression increased plant height and seed size. The grains of TIFY11b-overexpressing plants exceeded those of non-transformants in length, width and thickness, resulting in 9-21% increases in grain weight. The increase was achieved by overexpressing the gene in the whole plant body, but not by seed-restricted expression, indicating that seed enlargement is attributable to overexpression in vegetative organs such as the leaf. The whole-body overexpressing plants developed longer leaves along with higher levels of starch and sucrose in the leaf sheath and culm at the heading stage than the non-transformants. Although overexpression of TIFY11b did not alter the photosynthetic rate per leaf area before and after heading, it caused an accumulation of higher levels of the carbohydrate assimilate, probably due to increased photosynthesis per plant, suggesting that the increase in grain size and weight is attained by enhanced accumulation and translocation of the carbohydrate in the culms and leaf sheaths of the transgenic plants. Thus, TIFY11b is a novel grain-size increasing gene.
authors.affiliation: Hokuriku Research Center, National Agricultural Research Center, 1-2-1 Inada, Joetsu, Niigata 943-0193, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hakata
authors.forename: Masaharu
authors.initials: M
authors.lastname: Kuroda
authors.forename: Akihiro
authors.initials: A
authors.lastname: Ohsumi
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Hirose
authors.forename: Hidemitsu
authors.initials: H
authors.lastname: Nakamura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Muramatsu
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ichikawa
authors.forename: Hiromoto
authors.initials: H
authors.lastname: Yamakawa
mesh_terms: D050260:Carbohydrate Metabolism / Q000235:genetics*; D002523:Edible Grain / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D015870:Gene Expression; D017343:Genes, Plant / Q000235:genetics*; D012275:Oryza / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism*; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
chemical_list: D013395:Sucrose; D013213:Starch