Loss of chloroplast trnLUAA intron in two species of Hedysarum (Fabaceae): evolutionary implications

Document Type : Research Paper


1 Department of Plant Biology, Faculty of Biological Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, I.R. Iran.

2 2Department of Botany, Research Institute of Forests and Rangelands, P.O. Box 13185-116, Tehran, I.R. Iran.


Previous studies have indicated that in all land plants examined to date, the chloroplast gene trnLUAA is
interrupted by a single group I intron ranging from 250 to over 1400 bp. The parasitic Epifagus virginiana has
lost, however, the entire gene. We report that the intron is missing from the chloroplast genome of two
arctic species of the legume genus Hedysarum (H. alpinum, H. boreale). DNA sequencing of the trnL gene
and trnL-trnF intergenic spacer (trnL-F), as well as portion of trnF exon in these species confirms the
absence of trnL intron and shows that it has been deleted from the gene precisely along established
exon/intron splicing sites. Phylogenetic analysis of trnL-F sequence data revealed that they are closely
related species. This indicates that the intron was lost from the chloroplast genome before the divergence of
the two Hedysarum species. It is concluded that this rare genomic structural mutation may have occurred
once during the evolution of land plants.