Identification of transcribed and persistent variants of the psbA gene carried by plastid minicircles in a dinoflagellate.
Plastid genomes of the peridinin-containing dinoflagellates are composed of a limited number of genes that are contained separately on small circular molecules (minicircles). It has been shown that occasionally aberrant minicircles are generated, but they are usually small and contain little coding information. In this study, we discovered multiple variants, a putative "gene family", of the gene psbA in the plastid minicircles of the dinoflagellate Alexandrium tamarense, which have persisted for almost 3 years in culture. Each variant, like the ordinary psbA, existed on distinct minicircles of similar size (5-6 kb). 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. Each psbA variant might have been generated by DNA recombination and/or replication slippage, as for previously reported aberrant 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.
Iida
Satoko
S
Kobe University Research Center for Inland Seas, 2746 Iwaya, Awaji 656-2401, Japan.
Kobiyama
Atsushi
A
Ogata
Takehiko
T
Murakami
Akio
A
D001483:Base Sequence; D017931:DNA Primers; D004141:Dinoflagellida / Q000235:genetics*; D008969:Molecular Sequence Data; D045332:Photosystem II Protein Complex / Q000235:genetics*; D018087:Plastids; D020133:Reverse Transcriptase Polymerase Chain Reaction
D017931:DNA Primers; D045332:Photosystem II Protein Complex; C422369:photosystem II, psbA subunit