CLONING AND CHARACTERIZATION OF THE NUCLEAR GENE ENCODING PLASTID GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE FROM THE MARINE RED ALGA GRACILARIA-VERRUCOSA

The single-copy nuclear gene (GapA), encoding the plastid-localized gl yceraldehyde-3-phosphate dehydrogenase (GAPDH) of the marine red al,oa Gracilaria verrucosa, has been cloned and sequenced. The GapA transcr iptional initiation site was located 49 bp upstream of the start codon , and a putative TATA box was found 54 bp farther upstream. A spliceos omal intron was identified in the transit-peptide-encoding region in a position very similar to intron 1 of GapA and GapB of higher plants; no introns occur in the region encoding the mature protein. These obse rvations provisionally suggest that both red algae and higher plants d escend from a single ancestral pho tosynthetic eukaryote, i.e. that a single endosymbiotic event gave rise to red algal and higher-plant pla stids.