Abstract Detail

Recent Topics Posters

Schardl , Christopher Lewis [1], Calie, Patrick J [2], Jaromczyk, Jerzy W [3], Yoshida, Ruriko [4], Young, Carolyn A [5].

HGT alternatives: Trans-species polymorphism, paralogy and loss, and frequency dependent selection in alkaloid biosynthesis genes.

Wide (inter-family) horizontal gene transfer (HGT, a.k.a. lateral gene transfer) is increasingly invoked to explain phylogenetic patterns exhibited by certain gene classes in fungi, especially secondary metabolism genes. Curiously, wide HGT claims generally involve the “flexible genome,” which is comprised of conditionally dispensable genes, rather than the “core genome” which is comprised of housekeeping genes. Support for wide HGT is fundamentally parsimony based, but requires weighting of HGT vs alternative explanations in the absence of empirical evidence; begging the question, how should one weigh a process that was never observed experimentally against others with known mechanisms, some of which typify the flexible genome? The genome sequences were determined for more than 25 ascomycetes that produced one or more of the alkaloid types, ergot alkaloids, indole-diterpenes, lolines and peramine. Most of these fungi are Clavicipitaceae that are symbiotic or parasitic on plants. Phylogenies of alkaloid genes compared to housekeeping genes supported instances of trans-species polymorphism and paralogy. Comparative genomics indicated frequent gene losses, a process that we have also observed experimentally. Population surveys suggested that frequency-dependent selection functions to keep low but non-zero frequencies of alkaloid genes within sexual species, whereas the same genes are much more frequent in vertically transmitted plant symbionts. Finally, though one HGT event seemed evident, it appeared to involve members of the same genus (Epichloë) and the absence of effective vegetative incompatibility barriers.

1 - University Of Kentucky, Department Of Plant Pathology, 201F PLANT SCIENCES BLDG, 1405 VETERANS DRIVE, LEXINGTON, KY, 40546-0312, USA
2 - EASTERN KENTUCKY UNIVERSITY, LIFE SCIENCES, 349 MOORE SCIENCE BUILDING, 521 Lancaster Ave, RICHMOND, KY, 40475-3124, USA
3 - University of Kentucky, Computer Science, Lexington, KY, 40506, USA
4 - University of Kentucky, Statistics, Lexington, KY, 40506, USA
5 - The Samuel Roberts Noble Foundation, Forage Improvement, Ardmore, OK, 73401, USA

Keywords:
Genome Evolution
secondary metabolites
horizontal.

Presentation Type: Recent Topics Poster
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PRT048
Abstract ID:1834
Candidate for Awards:None