Evolutionary reshuffling in the Errantivirus lineage Elbe within the Beta vulgaris genome

Summary

LTR retrotransposons and retroviruses are closely related. While a viral envelope gene is found in some LTR retrotransposons and all retroviruses, only the latter have the ability of infectivity. The identification of Ty3‐gypsy‐like retrotransposons possessing putative envelope‐like open reading frames (ORFs) blurred the taxonomical borders and led to the establishment of the Errantivirus, Metavirus and Chromovirus genera within the Metaviridae. Only a few plant Errantiviruses have been described and their evolutionary history is not well understood. In this study we investigated 27 retroelements of four abundant Elbe retrotransposon families belonging to the Errantiviruses in Beta vulgaris (sugar beet). Retroelements of the Elbe lineage integrated between 0.02 Mya and 5.59 Mya, and show family‐specific variations in autonomy and degree of rearrangements: While Elbe3 members are highly fragmented, often truncated and present in a high number of solo‐LTRs, Elbe2 members are mainly autonomous. We observed extensive reshuffling of structural motifs across families leading to the formation of new retrotransposon families. Elbe retrotransposons harbor the typical envelope‐like gene often containing transmembrane domains. During the course of Elbe evolution, the additional ORFs have been strongly modified or independently acquired. Taken together, the Elbe lineage serves as retrotransposon model reflecting the different stages in Errantivirus evolution and allows a detailed analysis of retrotransposon family formation.

© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd