Although Rhesus (Rh) proteins are best known as antigens on human red blood cells, they are not restricted to red cells or to mammals, and hence their primary biochemical functions can be studied in more tractable organisms. We previously established that the Rh1 protein of the green alga Chlamydomonas reinhardtii is highly expressed in cultures bubbled with air containing high CO2 (3%), conditions under which Chlamydomonas grows rapidly. By RNA interference, we have now obtained Chlamydomonas rh mutants (epigenetic), which are among the first in nonhuman cells. These mutants have essentially no mRNA or protein for RH1 and grow slowly at high CO2, apparently because they fail to equilibrate this gas rapidly. They grow as well as their parental strain in air and on acetate plus air. However, during … Continue reading Lack of the Rhesus protein Rh1 impairs growth of the green alga Chlamydomonas reinhardtii at high CO2