Abstract
Selaginella moellendorfii (spikemoss) sequence trace data encoding a polypeptide highly similar to angiosperm and moss phage-type organelle RNA polymerases (RpoTs) were used to isolate a BAC clone containing the full-length gene SmRpoT as well as the corresponding cDNA. The SmRpoT mRNA comprises 3452 nt with an open reading frame of 3006 nt, encoding a putative protein of 1002 amino acids with a molecular mass of 113 kDa. The SmRpoT gene comprises 19 exons and 18 introns, conserved in their position with those of the angiosperm and Physcomitrella RpoT genes. In phylogenetic analyses, the Selaginella RpoT polymerase is in a sister position to all other phage-type polymerases of angiosperms. However, according to its conserved exon-intron structure, the Selaginella RpoT gene is representative of the molecular evolutionary lineage giving rise to the RpoT gene family of flowering plants. The N-terminal transit peptide of SmRpoT is shown to confer targeting of green fluorescent protein exclusively to mitochondria after transient expression in Arabidopsis and Selaginella protoplasts. Angiosperms and the moss P. patens possess small gene families encoding RpoTs, which include mitochondrial- and chloroplast-targeted RNA polymerases. In striking contrast, the Selaginella RpoT gene is shown to be single-copy, although Selaginella, as a lycophyte, has a phylogenetic position between Physcomitrella and angiosperms. Thus, there is no evidence that Selaginella may contain a nuclear-encoded phage-type chloroplast RNA polymerase.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.