Abstract
The peridinin-containing dinoflagellate is an algal group of Alveolata with plastids that originated from secondary endosymbiosis involving a red algal lineage. Plastomes of the peridinin-containing dinoflagellates are composed of a limited number of genes that are contained separately on small circular molecules, termed minicircles. We discovered multiple variants of the gene psbA in the minicircles of the dinoflagellate Alexandrium tamarense, which have persisted for almost three years in culture. Each variant, like the ordinary psbA, existed on distinct minicircles of similar size. These psbA variants retained all, or almost all, the coding sequence of the ordinary gene and all four were transcribed and edited after transcription, even though they could not encode the entire protein due to intervening or translocated sequences. Repeat elements were generally found in the relatively large non-coding region of these minicircles. The fact that these minicircles are transcribed, individually edited and maintained in the genome suggests that they are functionally important, although their precise roles remain unclear.
