Novel clades of chromodomain-containing Gypsy LTR retrotransposons from mosses (Bryophyta)

Retrotransposons are the major component of plant genomes. Chromodomain-containing Gypsy long terminal repeat (LTR) retrotransposons are widely distributed in eukaryotes. Four distinct clades of chromodomain-containing Gypsy retroelements are known from the vascular plants: Reina, CRM, Galadriel and Tekay. At the same time, almost nothing is known about the repertoire of LTR retrotransposons in bryophyte genomes. We have combined a search of chromodomain-containing Gypsy retroelements in Physcomitrella genomic sequences and an experimental investigation of diverse moss species. The computer-based mining of the chromodomain-containing LTR retrotransposons allowed us to describe four different elements from Physcomitrella. Four novel clades were identified that are evolutionarily distinct from the chromodomain-containing Gypsy LTR retrotransposons of other plants.