Figure 1.

C. reinhardtii sexual life cycle and sequenced samples. Vegetative C. reinhardtii cells of each mating type (MT+ and MT−) can be induced to undergo gametogenesis by nitrogen starvation. Gametes of opposite mating type recognize each other through flagellar adhesion and fuse to form a diploid zygote. During zygote maturation, MT− cpDNA is eliminated, flagella are resorbed, and a thick zygote cell wall forms. Upon return to nitrogen and light, zygospores undergo meiosis to form four haploid progeny (two of each mating type, all containing uniparentally inherited MT+ parental cpDNA) that reenter the vegetative cycle. Colored boxes designate samples and material sequenced. Blue and red unfilled circles represent MT+ and MT– chloroplast genomes, respectively. Filled pink and light blue circles represent nuclear DNA from MT+ and MT– strains, respectively. BS-Seq, Bisulfite sequencing.