Data Sheet 2_Chloroplast DNA minicircles composition, structure, and variation within Breviolum psygmophilum (Symbiodiniaceae, dinoflagellates).pdf

Past studies that have identified minicircles in Symbiodiniacae have used minicircles from other algal taxa as a starting point for discovery and thus the full minicircle complement is unknown. Here we have used rolling circle amplification (RCA), an unbiased methodology, to identify circular DNA in the algae Breviolum psygmophilum (formerly Symbiodiaceae Clade B). The amplified minicircles were sequenced via Illumina MiSeq and Oxford Nanopore Technologies.

Using this approach, we determined that B. psygmophilum cpDNA contains 14 minicircles, 4 of which have more than one variant. In addition, the relative abundance of individual minicircles is plastic, varying across physiological stages from the linear growth phase and the early declining growth phase. These observations raise the possibility that the evolution of chloroplast minicircles may provide a means of modulating gene dosage through variation in DNA relative abundance, a level of flexibility that may not be readily achievable in the typical single-circular chloroplast genomes found in most plants and algae.</p>