Introgression of C4 Pathway Gene(s) in C3 Plants to Improve Photosynthetic Carbon Assimilation for Crop Improvement: A Biotechnological Approach

Abstract

Environmental abiotic stresses including salinity, drought, temperature, and elevated CO2 lead to adverse effects on photosynthesis and crop productivity. Photosynthesis is a prominent biological process, which converts atmospheric CO2 into an organic compound. There are three different methods of carbon assimilation, and based on which, plants are categorized as C3, C4, or CAM. Among all the types, C4 plants are considered the most productive with low photorespiration, and high water- and nitrogen-use efficiency, compared to C3 plants. The enzymes involved in C4 photosynthesis carbon assimilation, also play a fundamental role in the plant's defence response to different abiotic and biotic stresses. The majority of agriculture crops, rice, wheat, soybean, and potato possess C3 carbon assimilation and encounter low photosynthesis, and high photorespiration under stress conditions. Gene introgression is one of the most reliable, and cost-effective approachs for improving crops, and C4 photosynthetic enzyme-encoding genes are considered potential candidates for enhanced carbon assimilation and stress tolerance. In this chapter, different biological routes of CO2 assimilation, types of C4 pathways, the evolution of C4 plants, and the effect of elevated CO2 on C3 and C4 plants are discussed. The chapter deals with the study of the physiology of C3 plants overexpressing C4 photosynthetic genes. However, expression of single or multiple C4 genes in C3 plants showed both positive and negative effects. Moreover, this approach of C3 plant improvement provides a useful insight to improve carbon assimilation under challenging climate change for better performance of photosynthesis and increased biomass production of C3 plants.