title: Fine Mapping ofCarbon Assimilation Rate 8, a Quantitative Trait Locus for Flag Leaf Nitrogen Content, Stomatal Conductance and Photosynthesis in Rice.
abstract: Increasing the rate of leaf photosynthesis is one important approach for increasing grain yield in rice (Oryza sativa). Exploiting the natural variation in CO2assimilation rate (A) between rice cultivars using quantitative genetics is one promising means to identify genes contributing to higher photosynthesis. In this study, we determined precise location ofCarbon Assimilation Rate 8(CAR8) by crossing a high-yieldingindicacultivar with a Japanese commercial cultivar. Fine mapping suggested thatCAR8encodes a putative Heme Activator Protein 3 (OsHAP3) subunit of a CCAAT-box-binding transcription factor called OsHAP3H. Sequencing analysis revealed that theindicaallele ofCAR8has a 1-bp deletion at 322 bp from the start codon, resulting in a truncated protein of 125 amino acids. In addition,CAR8is identical toDTH8/Ghd8/LHD1, which was reported to control rice flowering date. The increase ofAis largely due to an increase of RuBP regeneration rate via increased leaf nitrogen content, and partially explained by reduced stomatal limitation via increased stomatal conductance relative toA. This allele also increases hydraulic conductivity, which would promote higher stomatal conductance. This indicates thatCAR8affects multiple physiological aspects relating to photosynthesis. The detailed analysis of molecular functions ofCAR8would help to understand the association between photosynthesis and flowering and demonstrate specific genetic mechanisms that can be exploited to improve photosynthesis in rice and potentially other crops.
authors.affiliation: Department of Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and TechnologyFuchu, Japan; Institute of Global Innovation Research, Tokyo University of Agriculture and TechnologyFuchu, Japan; Precursory Research for Embryonic Science and Technology, Japan Science and Technology AgencyKawaguchi, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Adachi
authors.affiliation: Department of Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology Fuchu, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yoshikawa
authors.affiliation: Institute of Crop Science, National Agriculture and Food Research Organization Tsukuba, Japan.
authors.forename: Utako
authors.initials: U
authors.lastname: Yamanouchi
authors.affiliation: Department of Frontier Research, Kazusa DNA Research Institute Kisarazu, Japan.
authors.forename: Takanari
authors.initials: T
authors.lastname: Tanabata
authors.affiliation: Institute of Crop Science, National Agriculture and Food Research OrganizationTsukuba, Japan; Rice Research Institute, Shenyang Agricultural UniversityShenyang, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and TechnologyFuchu, Japan; Institute of Global Innovation Research, Tokyo University of Agriculture and TechnologyFuchu, Japan.
authors.forename: Taiichiro
authors.initials: T
authors.lastname: Ookawa
authors.affiliation: Institute of Crop Science, National Agriculture and Food Research Organization Tsukuba, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Institute of Global Innovation Research, Tokyo University of Agriculture and TechnologyFuchu, Japan; Department of Ecology and Evolutionary Biology, University of TorontoToronto, ON, Canada.
authors.forename: Rowan F
authors.initials: RF
authors.lastname: Sage
authors.affiliation: Department of Biological Production Science, Graduate School of Agriculture, Tokyo University of Agriculture and TechnologyFuchu, Japan; Institute of Global Innovation Research, Tokyo University of Agriculture and TechnologyFuchu, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hirasawa
authors.affiliation: Institute of Crop Science, National Agriculture and Food Research Organization Tsukuba, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Yonemaru
keywords: Oryza sativa; RuBP regeneration; leaf nitrogen content; photosynthesis; quantitative trait locus; stomatal conductance