title: Photosynthetic characteristics in genetically modified sense-RbcS silver birch lines.
abstract: Transgenic silver birch lines carrying extra copies of endogenous small subunit of Rubisco (RbcS)-gene under 35S CaMV promoter were used to study the carbon use efficiency of silver birch (Betula pendula Roth). A five week greenhouse experiment was carried out with four transgenic lines, R3.2, R7.2, E5 and E25, and their corresponding wild types (wt). The first fully developed leaves were used for analyses. Three of the produced lines, R3.2, E5 and E25, differed from the wt lines. Line R3.2 showed an altered growth rhythm; its chlorophyll content, Rubisco amount and activity as well as photosynthetic characteristics were reduced at the beginning of the experiment, which resulted in decreased biomass and growth. In lines E25 and E5, the biomass accumulation was shifted to roots, and in line E25, the total biomass was also reduced. In line E25, the differences were particularly marked in the dry mass, indicating a difference in water use, seen as increased transpiration. Introduction of sense RbcS decreased the Rubisco amount in birch leaves to 80% of wt at times during the tree development, but the lower amount of Rubisco was usually not seen in photosynthesis. The accumulation and distribution of biomass within the plants was altered.
authors.affiliation: Finnish Forest Research Institute, Punkaharju Research Unit, 58450 Punkaharju, Finland. sari.kontunen-soppela@uef.fi
authors.forename: Sari
authors.initials: S
authors.lastname: Kontunen-Soppela
authors.forename: Maarit
authors.initials: M
authors.lastname: Sillanpää
authors.forename: Eeva-Maria
authors.initials: EM
authors.lastname: Tuhkanen
authors.forename: Sirkka
authors.initials: S
authors.lastname: Sutinen
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kangasjärvi
authors.forename: Elina
authors.initials: E
authors.lastname: Vapaavuori
authors.forename: Hely
authors.initials: H
authors.lastname: Häggman
mesh_terms: D029662:Betula / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D018628:Gene Dosage; D017343:Genes, Plant; D010788:Photosynthesis / Q000235:genetics*; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics* / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D002734:Chlorophyll; D012273:Ribulose-Bisphosphate Carboxylase