N-terminal acetyltransferase 3 gene is essential for robust circadian rhythm of bioluminescence reporter in Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii is a model species of algae for studies on the circadian clock. Previously, we isolated a series of mutants showing defects in the circadian rhythm of a luciferase reporter introduced into the chloroplast genome, and identified the genes responsible for the defective circadian rhythm. However, we were unable to identify the gene responsible for the defective circadian rhythm of the rhythm of chloroplast 97 (roc97) mutant because of a large genomic deletion. Here, we identified the gene responsible for the roc97 mutation through a genetic complementation study. This gene encodes a protein that is homologous to the subunit of N-terminal acetyltransferase (NAT) which catalyzes N-terminal acetylation of proteins. Our results provide the first example of involvement of the protein N-terminal acetyltransferase in the circadian rhythm.