Phosphoenol pyruvate carboxylase (PEPC) is a ubiquitous cytoplasmic enzyme present in vascular plants and is also widely distributed among archeal, bacterial, cyanobacterial and unicellular green algal species. PEPC is clearly best known for its cardinal roles in C4- photosynthesis and CAM. Most of the vegetative, fruit and crop plants are C3 plants. The main problem with C3 plants is that they can’t tolerate the harsh conditions like drought and hot climates. C4 and CAM plants have special adaptations that enable them to survive in the hot and dry conditions. C4 and CAM plants have mechanism to control the photorespiration. One of such adaptation is the presence of enzyme PEPC. This enzyme catalyzes the irreversible β-carboxylation of PEP in the presence of HCO3 and Mg2 to yield oxaloacetate (4-C compound) and inorganic phosphate. Then 4-C compounds are transported to bundle sheath cells where bound carbon is released again as CO₂. One of the challenges that plant biotechnologists are facing is to modify the photosynthesis of C3 plants in order to achieve the increase in net carbon gain. Initially they were interested in engineering RuBisCo in order to increase its carboxylase activity as compare to oxygenase activity, but it has not been possible yet. Today main interest is to transfer the C4 traits in C3 plants to improve their photosynthetic characteristics and to make them stress tolerant. In modern day genetic engineering the Agrobacterium tumefaciens mediated gene transfer system is widely used to transform the plants. In current project, our aim is to transform local variety of tomato by cyanobacterial pepc gene using the Agrobacterium tumefaciens mediated gene transfer system. In the long run we intend to develop tomato plants with C4 plants like characteristics that demonstrate better growth and development in harsh environments.