Eric H Lyons

PMID: 18836034;PMCID: PMC2593585;Abstract:

Previous to this work, typical genes were thought to move from one position to another infrequently. On the contrary, we now estimate that between one-fourth and three-fourths of the genes in Arabidopsis transposed in the Brassicales. We used the CoGe comparative genomics system to perform and visualize multiple orthologous chromosomal alignments. Using this tool, we found large differences between different categories of genes. Ten of the gene families examined, including genes in most transcription factor families, exhibited a median frequency of 5% transposed genes. In contrast, other gene families were composed largely of transposed genes: NB-LRR disease-resistance genes, genes encoding MADS-box and B3 transcription factors, and genes encoding F-box proteins. A unique method involving transposition-rich regions of genome allowed us to obtain an indirect estimate of the positional stability of the average gene. The observed differences between gene families raise important questions concerning the causes and consequences of gene transposition. ©2008 by Cold Spring Harbor Laboratory Press.

PMID: 20495794;PMCID: PMC2886086;Abstract:

Local gene duplication is a prominent mechanism of gene copy number expansion. Elucidating the mechanisms by which local duplicates arise is necessary in understanding the evolution of genomes and their host organisms. Chromosome one of Arabidopsis thaliana contains an 81-gene array subdivided into 27 triplet units (t-units), with each t-unit containing three pre-transfer RNA genes. We utilized phylogenetic tree reconstructions and comparative genomics to order the events leading to the array's formation, and propose a model using unequal crossing-over as the primary mechanism of array formation. The model is supported by additional phylogenetic information from intergenic spacer sequences separating each t-unit, comparative analysis to an orthologous array of 12 t-units in the sister taxa Arabidopsis lyrata, and additional modeling using a stochastic simulation of orthologous array divergence. Lastly, comparative phylogenetic analysis demonstrates that the two orthologous t-unit arrays undergo concerted evolution within each taxa and are likely fluctuating in copy number under neutral evolutionary drift. These findings hold larger implications for future research concerning gene and genome evolution. © 2010 The Author(s).