title: Hybrid Rubisco of tomato large subunits and tobacco small subunits is functional in tobacco plants.
abstract: Biogenesis of functional ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in plants requires specific assembly in the chloroplast of the imported, cytosol-synthesized small subunits (SS) with the chloroplast-made large subunits (LS). Accumulating evidence indicates that chloroplasts (plastids) generally have a low tolerance for assembling foreign or modified Rubisco. To explore Rubisco engineering, we created two lines of transplastomic tobacco plants whose rbcL gene was replaced by tomato-derived rbcL: plant LLS2 with Rubisco composed of tobacco SS and Q437R LS and plant LLS4 with a hybrid Rubisco of tobacco SS and tomato LS (representing four substitutions of Y226F, A230T, S279T and Q437R from tobacco LS). Plant LLS2 exhibited similar phenotypes as the wild type. Plant LLS4 showed lower chlorophyll and Rubisco levels particularly in young emerging leaves, lower photosynthesis rates and biomass during early stages of development, but was able to reach reproductive maturity and somewhat wild type-like phenotype under ambient CO₂ condition. In vitro assays detected similar carboxylase activity and RuBP affinity in LLS2 and LLS4 plants as in wild type. Our studies demonstrated that tomato LS was sufficiently assembled with tobacco SS into functional Rubisco. The hybrid Rubisco of tomato LS and tobacco SS can drive photosynthesis that supports photoautotrophic growth and reproduction of tobacco plants under ambient CO₂ and light conditions. We discuss the effect of these residue substitutions on Rubisco activity and the possible attribution of chlorophyll deficiency to the in planta photosynthesis performance in the hybrid Rubisco plants.
authors.affiliation: Department of Biological Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA. xhzhang@fau.edu
authors.forename: Xing-Hai
authors.initials: XH
authors.lastname: Zhang
authors.forename: James
authors.initials: J
authors.lastname: Webb
authors.forename: Yi-Hong
authors.initials: YH
authors.lastname: Huang
authors.forename: Li
authors.initials: L
authors.lastname: Lin
authors.forename: Ri-Sheng
authors.initials: RS
authors.lastname: Tang
authors.forename: Aimin
authors.initials: A
authors.lastname: Liu
mesh_terms: D018533:Biomass; D002245:Carbon Dioxide / Q000502:physiology; D002678:Chimera / Q000235:genetics* / Q000378:metabolism; D002734:Chlorophyll / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D017343:Genes, Plant; D008027:Light; D018551:Solanum lycopersicum / Q000235:genetics*; D010641:Phenotype; D010788:Photosynthesis / Q000235:genetics* / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000502:physiology; D021122:Protein Subunits / Q000235:genetics* / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics* / Q000502:physiology
chemical_list: D010940:Plant Proteins; D021122:Protein Subunits; D002734:Chlorophyll; D002245:Carbon Dioxide; D012273:Ribulose-Bisphosphate Carboxylase