Towards efficient photosynthesis: overexpression of Zea mays phosphoenolpyruvate carboxylase in Arabidopsis thaliana

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• 作者：Deepika Kandoi ; Sasmita Mohanty ; Govindjee ; Baishnab C. Tripathy
• 关键词：Arabidopsis thaliana ; C4 photosynthesis ; Chl a fluorescence ; CO2 assimilation ; Phosphoenolpyruvate carboxylase ; Salt stress
• 刊名：Photosynthesis Research
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：130
• 期：1-3
• 页码：47-72
• 全文大小：2,853 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Plant Physiology
  
• 出版者：Springer Netherlands
• ISSN：1573-5079
• 卷排序：130

文摘

Plants with C4 photosynthesis are efficient in carbon assimilation and have an advantage over C3 photosynthesis. In C4 photosynthesis, the primary CO₂ fixation is catalyzed by phosphoenolpyruvate carboxylase (PEPC). Here, we show that overexpression of Zea mays PEPC cDNA, under the control of 35S 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 CO₂ assimilation, 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 (F_v/F_m) 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.