Fungi ligE-type glutathione S-transferases horizontally transferred into plants and a protozoan

Abstract

Horizontal gene transfers (HGT) were considered as common evolution approaches for organisms. However, most HGT especially those HGT among distant species, like microbes to plants, were over-estimated because they were just identified based on the criteria of Blast searches and gene tree-species tree reconciliation. Recently, a ligE-type glutathione S-transferase (GST), Fhb7-GST was considered as an HGT from Epichloe to Thinopyrum elongatum. To confirm and clarify the occurring patterns of this HGT, homologue searches were conducted. Although TeFhb7-GST was not found in other plants, ligE-GSTs were found in not only plants but also an ameba protozoan. Additionally, ligE-GSTs were likely to horizontally transfer from fungi to other organisms. LigE-GSTs evolve in various fungi, but they only exist in some liverworts and green algae. Interestingly, all these ligE-GST genes in these plants share more than 90% similarities with that from fungus Coniosporium apollinis. More than that, the protozoan homologue from Acanthamoeba castellanii have 94.9% similiarity with that from C. apollinis. Actually, only a few substitutions were found in two homologues except a 111-bp lost in A. castellanii ligE-GST. All these results suggested HGT is an important evolutionary method for all organisms. Notably, natural HGT remind us to reevaluate the transgenic crops.