A Functional Isopenicillin N Synthase in an Animal Genome

Abstract

Horizontal transfer of genes is widespread among prokaryotes, but is less common between microorganisms and animals. Here, we present evidence for the presence of a gene encoding functional isopenicillin N synthase, an enzyme in the β-lactam antibiotics biosynthesis pathway, in the genome of the soil-living collembolan species, Folsomia candida (FcIPNS). At present, this gene is only known from bacteria and fungi, as is the capacity to produce β-lactam antibiotics. The FcIPNS gene was located on two genomic contigs, was physically linked to a predicted insect ATP-binding cassette transporter gene, and contained three introns each flanked by eukaryotic splicing recognition sites (GT/AG). Homology searches revealed no similarity between these introns and the FcIPNS regions of bacteria or fungi. All amino acids conserved across bacteria and fungi were also conserved in F. candida. Recombinant FcIPNS was able to convert its substrate amino δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine into isopenicillin N, providing strong evidence that FcIPNS is functional. Phylogenetic analysis clustered FcIPNS outside the bacterial IPNS clade, and also outside the fungal IPNS clade, suggesting an ancient gene transfer followed by divergence in the F. candida genome. In conclusion, the data suggest that the soil-living collembolan F. candida has assimilated the capacity for antibacterial activity by horizontal gene transfer, which may be an important adaptive trait in the microbe-dominated soil ecosystem.

Collembolan Transcriptomes Highlight Molecular Evolution of Hexapods and Provide Clues on the Adaptation to Terrestrial Life

“…A variety of genetic mechanisms giving rise to new genes have been identified, including gene duplication, gene fusion and fission, exon shuffling, de novo origination from previously non-coding sequences and horizontal gene transfer [26]. Recently, we have identified horizontal gene transfer as a genetic mechanism that explains the presence of unique functional genes in collembolans [96]. The fact that F .…”

“…The fact that F . candida is the first animal that is equipped with a biosynthesis pathway for β-lactam antibiotics [96] underpins the importance of such evolutionary processes in this animal group.…”

Biochemical pathways supporting beta-lactam biosynthesis in the springtail Folsomia candida

“…Previously, we applied in situ hybridization to show that ACVS is localized and strongly induced in the gut epithelium of the animal (Nota et al, 2008). Furthermore, Roelofs et al (2013) showed that the formation of a beta-lactam can be catalyzed by beta-lactam biosynthesis genes belonging to the genome of Folsomia . Very recently, we detected and quantified beta-lactam compounds in Folsomia using an ELISA assay in vivo , and preliminary data show that this metabolite increases in abundance after heat shock treatment (W.S., unpublished data).…”

“…Biosynthesis of these compounds has been described in several species of Actinobacteria and Proteobacteria and in several fungi (Ozcengiz and Demain, 2013). It was not reported in animals until recently, when the first metazoan beta-lactam biosynthesis genes were characterized in the springtail Folsomia candida (Roelofs et al, 2013). Folsomia candida is a soil-dwelling basal hexapod, the closest relatives of the insects (Misof et al, 2014).…”

“…Beta-lactam biosynthesis genes are involved in the stress response of F. candida and are upregulated upon exposure to a variety of stressors (de Boer et al, 2015). Most probably, F. candida acquired its beta-lactam genes through horizontal gene transfer (Roelofs et al, 2013). However, in addition to the core biosynthesis pathway, other pathways are required for beta-lactam biosynthesis.…”