title: Increased Rubisco content in transgenic rice transformed with the 'sense' rbcS gene.
abstract: Rice (Oryza sativa L.) plants with substantially increased Rubisco content were obtained by Agrobacterium-mediated transformation with the rice rbcS sense gene under the control of the rice rbcS promoter. The primary transformants were screened for the ratio of Rubisco to leaf-N content, and the transformants with >120% wild-type levels of Rubisco were selected. In the progeny of the selected lines of the transformants, the mRNA levels of one member of the rbcS gene family were increased from 3.9- to 6.2-fold, whereas those of other members of the rbcS gene family were unchanged. The total levels of rbcS mRNA were increased from 2.1- to 2.8-fold. The levels of rbcL mRNA were increased from 1.2- to 1.9-fold. Rubisco protein content was significantly increased by 30% on a leaf area basis. The ratio of Rubisco-N to leaf-N was also increased by 10-20%, irrespective of N treatment. The specific activity of Rubisco per unit of enzyme protein was not different. However, light-saturated photosynthesis was not enhanced even when the rate was measured at low [CO2] where Rubisco becomes limiting for photosynthesis. Some lines showed lower photosynthesis at high [CO2] (>60 Pa). We conclude that introduction of additional sense rbcS leads to overexpression of rbcS and that this overexpression slightly up-regulates the gene expression of rbcL at the transcript level and enhances the amount of Rubisco holoenzyme. However, overproduction of Rubisco protein does not improve photosynthesis.
authors: Department of Applied Plant Science, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Sendai 981-8555, Japan.
authors: Yuji
authors: Y
authors: Suzuki
authors: Maki
authors: M
authors: Ohkubo
authors: Hanako
authors: H
authors: Hatakeyama
authors: Keiko
authors: K
authors: Ohashi
authors: Ryuichi
authors: R
authors: Yoshizawa
authors: Soichi
authors: S
authors: Kojima
authors: Toshihiko
authors: T
authors: Hayakawa
authors: Tomoyuki
authors: T
authors: Yamaya
authors: Tadahiko
authors: T
authors: Mae
authors: Amane
authors: A
authors: Makino
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D009584:Nitrogen / Q000378:metabolism; D012275:Oryza / Q000201:enzymology* / Q000235:genetics*; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics*
chemical_list: D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase; D009584:Nitrogen