title: Towards efficient photosynthesis: overexpression of Zea mays phosphoenolpyruvate carboxylase in Arabidopsis thaliana.
abstract: Plants with C4 photosynthesis are efficient in carbon assimilation and have an advantage over C3 photosynthesis. In C4 photosynthesis, the primary CO2fixation is catalyzed by phosphoenolpyruvate carboxylase (PEPC). Here, we show that overexpression of Zea mays PEPC cDNA, under the control of35S promoter, in Arabidopsis thaliana resulted in ~7-10 fold higher protein abundance and ~7-10 fold increase in PEPC activity in the transgenic lines than that in the vector control. We suggest that overexpression of PEPC played an anaplerotic role to increase the supply of 4-carbon carboxylic acids, which provided carbon skeletons for increased amino acid and protein synthesis. Higher protein content must have been responsible for increased metabolic processes including chlorophyll biosynthesis, photosynthesis, and respiration. Consequently, the PEPC-overexpressed transgenic plants had higher chlorophyll content, enhanced electron transport rate (ETR), lower non-photochemical quenching (NPQ) of chlorophyll a fluorescence, and a higher performance index (PI) than the vector control. Consistent with these observations, the rate of CO2assimilation, the starch content, and the dry weight of PEPC-overexpressed plants increased by 14-18 %, 10-18 %, and 6.5-16 %, respectively. Significantly, transgenics were tolerant to salt stress as they had increased ability to synthesize amino acids, including the osmolyte proline. NaCl (150 mM)-treated transgenic plants had higher variable to maximum Chl a fluorescence (Fv/Fm) ratio, higher PI, higher ETR, and lower NPQ than the salt-treated vector controls. These results suggest that expression of C4 photosynthesis enzyme(s) in a C3 plant can improve its photosynthetic capacity with enhanced tolerance to salinity stress.
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India.|School of Biotechnology, Kalinga Institute of Industrial Technology University, Bhubaneswar, Odisha, 751024, India.
authors.forename: Deepika
authors.initials: D
authors.lastname: Kandoi
authors.affiliation: School of Biotechnology, Kalinga Institute of Industrial Technology University, Bhubaneswar, Odisha, 751024, India.
authors.forename: Sasmita
authors.initials: S
authors.lastname: Mohanty
authors.affiliation: Department of Plant Biology, Department of Biochemistry and Center of Biophysics & Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
authors.lastname: Govindjee
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110067, India. bctripathy@mail.jnu.ac.in.
authors.forename: Baishnab C
authors.initials: BC
authors.lastname: Tripathy
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000378:metabolism; D015139:Blotting, Southern; D015153:Blotting, Western; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D018506:Gene Expression Regulation, Plant; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D010788:Photosynthesis; D055049:Salt Tolerance; D003313:Zea mays / Q000201:enzymology* / Q000378:metabolism
chemical_list: D002734:Chlorophyll; D002245:Carbon Dioxide; D010730:Phosphoenolpyruvate Carboxylase; D000077194:Chlorophyll A
keywords: Arabidopsis thaliana; C4 photosynthesis; CO2 assimilation; Chl a fluorescence; Phosphoenolpyruvate carboxylase; Salt stress