This project aims to test the hypothesis that an increase in purine biosynthesis and hence ureide biosynthesis in the nodules of transgenic winged bean (Psophocarpus tetragonolobus ), a tropical legume, will result in improved assimilation of fixed nitrogen, and hence increased overall plant productivity under symbiotic conditions. It necessitates: (i) the development of an efficient Agrobaclerium-mcdiaied transformation and regeneration protocol for a tropical legume; (ii) the isolation of purine biosynthetic cDNA clones from a mothbean (Vigna aconitifolia) nodule library by functional complementation of Escherichia coli auxotrophic mutants, and characterization of these clones; and (iii) the production of nodulated transgenic tropical legumes over-expressing glutamine phosphoribosyl amidotransferase (PRAT), the main regulatory enzyme in purine biosynthesis, in the nodules. If the proposed mode! is successful, this strategy can then be applied to improving the yields of regionally important legumes such as kidney bean (Phaseolus vulgaris) and pigeon pea (Cajanas cajart).