MOLECULAR-CLONING AND CHARACTERIZATION OF ADP-GLUCOSE PYROPHOSPHORYLASE CDNA CLONES ISOLATED FROM PEA COTYLEDONS

Three ADP-glucose pyrophosphorylase (ADPG-PPase) cDNA clones have been isolated and characterized from a pea cotyledon cDNA library. Two of these clones (Psagps1 and Psagps2) encode the small subunit of ADPG-PP ase. The deduced amino acid sequences for these two clones are 95% ide ntical. Expression of these two genes differs in that the Psagps2 gene shows comparatively higher expression in seeds relative to its expres sion in other tissues. Psagps2 expression also peaks midway through se ed development at a time in which Psagps1 transcripts are still accumu lating. The third cDNA isolated (Psagpl1) encodes the large subunit of ADPG-PPase. It shows greater selectivity in expression than either of the small subunit clones. It is highly expressed in sink organs (seed , pod, and seed coat) and undetectable in leaves.