CHLOROPLASTIC GENOMES OF GINKGO-BILOBA AND CHLAMYDOMONAS-MOEWUSII CONTAIN A CHLB GENE ENCODING ONE SUBUNIT OF A LIGHT-INDEPENDENT PROTOCHLOROPHYLLIDE REDUCTASE

We have cloned and sequenced a Chlamydomonas moewusii chloroplastic DN A fragment that includes a 563 amino-acid open reading frame (ORF563, chlB) presenting 89% amino-acid homology with ORF513 from Marchantia p olymorpha. It is also homologous to ORF510 from Pinus thunbergii but i ncludes two insertions absent in both M. polymorpha and P. thunbergii. The derived polypeptide is 54% similar to the product of bchB from Rh odobacter capsulatus, identified as one subunit of a light-independent NADH-protochlorophyllide reductase. We also isolated and sequenced an homologous chloroplastic gene from the gymnosperm Ginkgo biloba. Nort hern hybridizations performed on RNA isolated from synchronized Chlamy domonas eugametos cells showed higher expression between the tenth hou r of light and the eighth hour of darkness, peaking during the first 2 h of darkness.