Overexpression of an <i>Agave</i> Phospho<i>enol</i>pyruvate Carboxylase Improves Plant Growth and Stress Tolerance

• Main Authors: Degao Liu, Rongbin Hu, Jin Zhang, Hao-Bo Guo, Hua Cheng, Linling Li, Anne M. Borland, Hong Qin, Jin-Gui Chen, Wellington Muchero, Gerald A. Tuskan, Xiaohan Yang
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Cells
• Subjects: <i>Agave americana</i>; crassulacean acid metabolism; genetic engineering; <i>Nicotiana sylvestris</i>; phospho<i>enol</i>pyruvate carboxylase; photosynthesis
• Online Access: https://www.mdpi.com/2073-4409/10/3/582

It has been challenging to simultaneously improve photosynthesis and stress tolerance in plants. Crassulacean acid metabolism (CAM) is a CO₂-concentrating mechanism that facilitates plant adaptation to water-limited environments. We hypothesized that the ectopic expression of a CAM-specific phospho<i>enol</i>pyruvate carboxylase (PEPC), an enzyme that catalyzes primary CO₂ fixation in CAM plants, would enhance both photosynthesis and abiotic stress tolerance. To test this hypothesis, we engineered a CAM-specific <i>PEPC</i> gene (named <i>AaPEPC1</i>) from <i>Agave americana</i> into tobacco. In comparison with wild-type and empty vector controls, transgenic tobacco plants constitutively expressing <i>AaPEPC1</i> showed a higher photosynthetic rate and biomass production under normal conditions, along with significant carbon metabolism changes in malate accumulation, the carbon isotope ratio δ¹³C, and the expression of multiple orthologs of CAM-related genes. Furthermore, <i>AaPEPC1</i> overexpression enhanced proline biosynthesis, and improved salt and drought tolerance in the transgenic plants. Under salt and drought stress conditions, the dry weight of transgenic tobacco plants overexpressing <i>AaPEPC1</i> was increased by up to 81.8% and 37.2%, respectively, in comparison with wild-type plants. Our findings open a new door to the simultaneous improvement of photosynthesis and stress tolerance in plants.