IDENTIFICATION AND DNA SEQUENCE OF A NEW H+‐ATPase IN THE UNICELLULAR GREEN ALGA CHLAMYDOMONAS REINHARDTII (CHLOROPHYCEAE)

Insertional mutagenesis was used to identify genes involved in mating and/or zygote formation in the unicellular green alga Chlamydomonas reinhardtii Dangeard. Approximately 800 insertionally mutagenized transformants were examined, and a single nonagglutinating mutant was identified. Plasmid rescue was used to clone a genomic fragment containing transforming DNA. This fragment was then used to identify the wild‐type copy of the gene disrupted during mutagenesis. The wild‐type gene is transcribed during all stages of the life cycle and, based on sequence similarity, encodes a P2‐type proton transporting ATPase. The gene is referred to as Pmh1 for plasma membrane H+‐ATPase. PMH1 displays the greatest sequence similarity to ATPases from two parasitic flagellates and a raphidophytic alga but not to the ATPase from a closely related green alga. We propose that PMH1 represents a distinct H+‐ATPase isoform expressed in flagellates.