Optimization of carbon and nitrogen utilization for enhanced photosynthesis, biomass and yield by coexpression of phosphoenolpyruvate carboxylase , aspartate aminotransferase and glutamine synthetase in Brassica juncea

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Abstract
Summary: Coexpression of genes involved in carbon (C) and nitrogen (N) metabolism offers a promising avenue for improving crop yield. This study investigated the impact of coexpressing phosphoenolpyruvate carboxylase [ ZmPEPC ( P )], aspartate aminotransferase [ GmAspAT ( A )] and glutamine synthetase [ NtGS ( G )] in Brassica juncea to enhance plant yield through improved C and N utilization. Plants coexpressing three genes ( BjPAG ) showed a significant increase in plant growth, biomass, chlorophyll and carotenoid content, while exhibiting decreased anthocyanin and hydrogen peroxide production. These improvements were observed under both ambient (~400 ppm; ACO 2 ) and low (~200 ppm; LCO 2 ) atmospheric CO 2 conditions. Chlorophyll fluorescence study revealed that BjPAG plants had higher photosynthetic efficiency, particularly increased maximum quantum yield of PSII and performance index. This facilitated increased CO 2 assimilation, total soluble sugar and starch accumulation, along with altered stomatal traits under both ACO 2 and LCO 2 conditions. Additionally, BjPAG plants accumulated less ammonium than control plants under both CO 2 levels, indicating effective functioning of the overexpressed genes. Improved performance (enhanced photosynthetic rates, biomass and seed yield) of BjPAG plants under various N environments (6, 3 and 0.3 m m N) also supported improved N utilization. NMR analysis suggested that PAG ‐coexpression resulted in a higher flux of assimilated CO 2 and NH 3 towards sugars, amino acids, organic acids, polyphenols and glucosinolates. In conclusion, this study highlights the effectiveness of coexpressing ZmPEPC , GmAspAT and NtGS in B. juncea , leading to efficient C and N utilization, ultimately resulting in enhanced photosynthesis, plant biomass and seed yields, and as a promising strategy for increasing the yield of food crops.
Funding Information
  • Council of Scientific and Industrial Research, India (MLP‐0201)
  • Department of Science and Technology, Ministry of Science and Technology, India (WOS‐A)

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