The C4 rice project aims to install a C4 photosynthetic pathway into the C3 crop rice, predicted to improve photosynthetic efficiency, biomass and water use efficiency (Furbank, Kelly and von Caemmerer, 2023). This goal requires the expression of multiple genes at high levels and in the correct cell types. A minimal C4 cycle prototype has been generated in rice using five key enzymes derived from Zea mays on a single construct - carbonic anhydrase, phosphoenolpyruvate (PEP) carboxylase, NADP-malate dehydrogenase, pyruvate orthophosphate dikinase and NADP-malic enzyme (Ermakova et al., 2020). While able to support CO2 incorporation into C4 acids, these lines had very low malic enzyme activity (<2% of Zea mays). Subsequently, transgenic rice lines were generated using a synthetic promoter system (Danila et al., 2022), resulting in up to 50% of maize levels of NADP-malic enzyme localised to the bundle sheath chloroplasts. Crosses were made between these lines and the previously generated lines containing the remainder of the C4 pathway enzymes. These crosses expressed all five genes in the required cell types at 10-50% of maize expression levels. Glasshouse experiments on of the crossed lines showed no detrimental effects on plant growth or yield. Kinetic analysis of stomatal response phenotypes showed that high NADP-malic enzyme lines responded faster to changes in light intensity. These results suggest that introduction of even a partial C4 pathway in rice could benefit plants under higher and dynamic light environments in the field.