Abstract
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 phosphoenolpyruvate 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 PEPC gene (named AaPEPC1) from Agave americana into tobacco. In comparison with wild-type and empty vector controls, transgenic tobacco plants constitutively expressing AaPEPC1 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, AaPEPC1 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 AaPEPC1 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.
Highlights
Introduction iationsHuman population increases, global climate changes and natural resources reductions could seriously impact food and energy security in the future [1,2,3,4,5,6,7,8]
Through a tBLASTn search against A. americana transcriptomics data [28], using the phosphoenolpyruvate carboxylase (PEPC) protein sequences of Arabidopsis thaliana as queries, we identified a total of 21 transcripts encoding PEPC in A. americana
After we identified the crassulacean acid metabolism (CAM)-isoform of PEPC from A. americana, we wanted to dedetermine the impact of overexpressing this Agave gene on the photosynthetic carbon termine the impact of overexpressing this Agave gene on the photosynthetic carbon memetabolism and abiotic stress tolerance in Nicotiana sylvestris, which is a C3 plant tabolism and abiotic stress tolerance in Nicotiana sylvestris, which is a C3 plant species
Summary
Introduction iationsHuman population increases, global climate changes and natural resources reductions could seriously impact food and energy security in the future [1,2,3,4,5,6,7,8]. The drylands, with precipitation amounts that are inadequate for most present-day food and bioenergy crops, covers approximately 40% of the world’s land [9,10]. Around 20% of irrigated areas in the world are under salt stress which has become a big constraint limiting agricultural production [11,12,13]. The phytotoxic effects of nanoparticles could impact plant growth [14,15]. To address these challenges, tremendous efforts have been put into improving photosynthesis, drought tolerance and salt tolerance in crop plants through breeding and genetic engineering over the past 50 years, though there has been limited success in simultaneously enhancing both biomass production and stress tolerance [16].
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