MBE Advance Access originally published online on October 13, 2004
Molecular Biology and Evolution 2005 22(2):308-316; doi:10.1093/molbev/msi018
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Research Article |
A Functional Screen Identifies Lateral Transfer of ß-Glucuronidase (gus) from Bacteria to Fungi
Center for the Application of Molecular Biology to International Agriculture (CAMBIA), Canberra, Australia
E-mail peter{at}cambia.org.
Lateral gene transfer (LGT) from prokaryotes to microbial eukaryotes is usually detected by chance through genome-sequencing projects. Here, we explore a different, hypothesis-driven approach. We show that the fitness advantage associated with the transferred gene, typically invoked only in retrospect, can be used to design a functional screen capable of identifying postulated LGT cases. We hypothesized that ß-glucuronidase (gus) genes may be prone to LGT from bacteria to fungi (thought to lack gus) because this would enable fungi to utilize glucuronides in vertebrate urine as a carbon source. Using an enrichment procedure based on a glucose-releasing glucuronide analog (cellobiouronic acid), we isolated two gus+ ascomycete fungi from soils (Penicillium canescens and Scopulariopsis sp.). A phylogenetic analysis suggested that their gus genes, as well as the gus genes identified in genomic sequences of the ascomycetes Aspergillus nidulans and Gibberella zeae, had been introgressed laterally from high-GC gram+ bacteria. Two such bacteria (Arthrobacter spp.), isolated together with the gus+ fungi, appeared to be the descendants of a bacterial donor organism from which gus had been transferred to fungi. This scenario was independently supported by similar substrate affinities of the encoded ß-glucuronidases, the absence of introns from fungal gus genes, and the similarity between the signal peptide-encoding 5' extensions of some fungal gus genes and the Arthrobacter sequences upstream of gus. Differences in the sequences of the fungal 5' extensions suggested at least two separate introgression events after the divergence of the two main Euascomycete classes. We suggest that deposition of glucuronides on soils as a result of the colonization of land by vertebrates may have favored LGT of gus from bacteria to fungi in soils.
Key Words: Lateral gene transfer • gus • ß-glucuronidase • bacteria • fungi
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. Eudes, G. Mouille, J. Thevenin, A. Goyallon, Z. Minic, and L. Jouanin Purification, Cloning and Functional Characterization of an Endogenous beta-Glucuronidase in Arabidopsis thaliana Plant Cell Physiol., September 1, 2008; 49(9): 1331 - 1341. [Abstract] [Full Text] [PDF]
|
|