J Syst Evol ›› 2014, Vol. 52 ›› Issue (2): 134-148.DOI: 10.1111/jse.12070

• Research Articles • Previous Articles     Next Articles

Intron evolution in a phylogenetic perspective: Divergent trends in the two copies of the duplicated def gene in Impatiens L. (Balsaminaceae)

Ute VOLKMAR1*, Erik F. SMETS1,2, Henning LENZ3, Steven B. JANSSENS1,4   

  1. 1Section Ecology, Evolution and Biodiversity Conservation, Catholic University of Leuven (K.U.L.), Kasteelpark Arenberg 31, P.O. Box 2437, BE-3001 Leuven, Belgium
    2Naturalis Biodiversity Center (section NHN), Leiden University, PO Box 9517, NL-2300 RA Leiden, The Netherlands
    3Molecular Evolution, Institute for Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany
    4National Botanic Garden of Belgium, Domein van Bouchout, BE-1860 Meise, Belgium
  • Received:2013-07-04 Published:2014-01-21

Abstract: The history of MADS box genes is well-known in angiosperms. While duplication events and gene losses occur frequently, gene structure and intron positions are very conserved. We investigated all six introns in a duplicated MADS box gene (deficiens, def) in selected Impatiens taxa, thereby assessing intron features. For the first time, our study provides a comparison of molecular changes in all introns of a gene from a phylogenetic perspective. Interestingly, a uniform pattern of molecular evolution in the introns of each copy was not observed, but intron length increases, decreases, and size retention can be found in each copy. A tendency to accumulate long autapomorphic indels is also present, thus, a longer intron length does not reflect a higher number of parsimony-informative characters. Substitution rates vary between introns of each gene copy. While four of the six introns of def1 exhibit a change in their substitution rate, five of the six def2 introns maintain their rates throughout the genus albeit at different levels. In MADS box genes several regulatory sequences are found residing in introns. Thus, presence of putative regulatory motifs was investigated. Most of them are not conserved in position and usually present in only one of the gene copies. In addition, the potential for phylogenetic reconstruction of introns in both def copies is shortly discussed.

Key words: deficiens gene, Impatiens, intron evolution, phylogenetic potential, substitution rate.