Natural GMOs Part 193. Horizontal Gene Transfer Contributes to the Diversity of Fungal Metabolism

Genes move around microbes and fungi

The immense diversity of secondary metabolites found in fungal species raises the intriguing question of their evolutionary origin. Lateral or horizontal gene transfer (HGT) across species barriers has long been known for bacteria but was thought to play a minor role in the evolution of eukaryotic species.

However, recent data from genome sequencing studies have indicated that HGT has contributed considerably to this richness in metabolites [that is to say, chemicals made by fungi ] [14], [15].

 Investigation of 60 completely sequenced fungal genomes using strict phylogenomic criteria showed that 713 bacterial genes had been transferred to fungal genomes [16]. Several of these genes are involved in carbohydrate metabolism, allowing fungi to propagate under extreme environmental conditions. Early evidence that fungi acquired bacterial genes came from sequence comparison of beta-lactam antibiotic biosynthesis genes. The first two steps of beta-lactam antibiotic biosynthesis are catalyzed by a nonribosomal peptide synthetase and isopenicillin N synthase, leading to the intermediate isopenicillin N, which is common to all penicillins and their derivatives. Sequencing of the corresponding genes (pcbAB and pcbC) has provided evidence that these two genes are clustered in both bacteria and fungi (Figure 1). Furthermore, the clustered organization and the lack of any intronic sequences led to the assumption that bacterial beta-lactam antibiotic genes were transferred to fungal species such as A. nidulans, Penicillium chrysogenum, and Acremonium chrysogenum. The transfer of bacterial genes to a eukaryotic nucleus has a wide range of consequences. For example, the foreign genes have to adapt to the eukaryotic host system and its expression machinery. In prokaryotes, pathway-specific regulators commonly determine gene expression, while in eukaryotes, expression of secondary biosynthesis genes is often governed by global regulators. Good examples of such eukaryotic global regulators are LaeA and VeA, both part of a multi-subunit protein complex that controls the expression of genes, including those that encode beta-lactams, that are involved in fungal secondary metabolite processes [17], [18].

@ PLOS Pathogens: Putting Fungi to Work: Harvesting a Cornucopia of Drugs, Toxins, and Antibiotics:

The Pundit's reflection:
In other articles, detection of movement of genes between plants and fungi has been described. There are multitudes of natural GMOs.

Citations
14. Fitzpatrick DA (2012) Horizontal gene transfer in fungi. FEMS Microbiol Lett 329: 1–8. doi: 10.1111/j.1574-6968.2011.02465.x
Abstract
Horizontal gene transfer (HGT) is frequently observed in prokaryotes and until recently was assumed to be of limited importance to eukaryotes. However, there is an increasing body of evidence to suggest that HGT is an important mechanism in eukaryotic genome evolution, particularly in unicellular organisms. The transfer of individual genes, gene clusters or entire chromosomes can have significant impacts on niche specification, disease emergence or shift in metabolic capabilities. In terms of genomic sequencing, the fungal kingdom is one of the most densely sampled eukaryotic lineages and is at the forefront of eukaryote comparative genomics and enables us to use fungi to study eukaryotic evolutionary mechanisms including HGT. This review describes the bioinformatics-based methodologies commonly used to locate HGT in fungal genomes and investigates the possible mechanisms involved in transferring genetic material laterally into fungal species. I will highlight a number of fungal HGT events and discuss the impact they have played on fungal evolution and discuss the implications HGT may have on the fungal tree of life.


15. Teichert I, Nowrousian M (2011) Evolution of genes for secondary metabolism in fungi. In: Pöggeler S, Wöstemeyer J, editors. The Mycota XIV. Berlin, Heidelberg: Springer Verlag. pp. 231–255.