Identification of genes required for hydrogenase activity in Chlamydomonas reinhardtii

The eukaryotic green alga, Chlamydomonos reinhordtii, produces H-2 under anaerobic conditions, in a reaction catalysed by an [FeFe]-hydrogenase. To identify genes that influence H-2 production in C reinhordtii, a library of 6000 colonies on agar plates was screened with sensitive chemochromic H-2-sensor films for clones defective in H-2 production. Two mutants of particular interest were fully characterized. One mutant, hydEF-1, is unable to assemble an active [FeFe]-hydrogenase. This is the first reported C. reinhardtii mutant that is not capable of producing any H-2. The second mutant, sta7-10, is not able to accumulate insoluble starch and has significantly lowered H-2-photoproduction rates in comparison with the wild-type. in hydEF-1, anaerobiosis induces transcription of the two reported. C reinhardtii hydrogenase genes, HydA1 and HydA2, indicating a normal transcriptional response to anaerobiosis. in contrast, the transcription of both hydrogenase genes in sta7-10 is significantly attenuated.