History of the ADP/ATP-Translocase-Encoding Gene, a Parasitism Gene Transferred from a Chlamydiales Ancestor to Plants 1 Billion Years Ago

Abstract

Nonmitochondrial ADP/ATP translocase is an energy parasite enzyme. Its encoding gene, tlc , is found only in Rickettsiales , Chlamydiales , and plant and alga plastids. We demonstrate the presence of tlc in Parachlamydia acanthamoebae. This gene shares more similarity with the tlc 1 gene of Chlamydiaceae and the tlc of plant and alga plastids than with the tlc 2 gene of Chlamydiaceae . Phylogenetic analysis, including all other tlc homologs found in GenBank, showed that tlc was duplicated in a Chlamydiales ancestor before the appearance of multicellular eukaryotes. A time scale, calibrated with seven independent time points obtained from fossil estimates and from the 16S rRNA molecular clock, was congruent with the molecular clock provided by tlc . Plant and alga plastids acquired tlc approximately when Parachlamydiaceae and Chlamydiaceae diverged, at the eucaryotic radiation time, ca. 1 billion years ago.