MOLECULAR CHARACTERIZATION OF A NOVEL, NUCLEAR-ENCODED, NAD(-DEPENDENT GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE IN PLASTIDS OF THE GYMNOSPERM PINUS-SYLVESTRIS L())

Angiosperms and algae possess two distinct glyceraldehyde-3-phosphate dehydrogenase (GAPDH) enzymes, an NAD(+)-dependent tetramer involved i n cytosolic glycolysis and an NADP(+)-dependent enzyme of the Calvin c ycle in chloroplasts. We have found that the gymnosperm Pinus sylvestr is possesses, in addition to these, a nuclear-encoded, plastid-specifi c, NAD(+)-dependent GAPDH, designated GapCp, which has not previously been described from any plant. Several independent full-size cDNAs for this enzyme were isolated which encode a functional transit peptide a nd mature subunit very similar to that of cytosolic GAPDH of angiosper ms and algae. A molecular phylogeny reveals that chloroplast GapCp and cytosolic GapC arose through gene duplication early in chlorophyte ev olution. The GapCp gene is expressed as highly as that for GapC in lig ht-grown pine seedlings. These findings suggest that aspects of compar tmentalized sugar phosphate metabolism may differ in angiosperms and g ymnosperms and furthermore underscore the contributions of endosymbiot ic gene transfer and gene duplication to the nuclear complement of gen es for enzymes of plant primary metabolism.