Investigations of the coxII intron structure in the mitochondrial genes of angiosperms

The molecular structure of the intron of the mitochondrial gene coding for cytochrome oxidase susbunit II has been investigated by sequence analysis in eight angiosperm orders. Comparison of the overall primary structure of the intron, made with respect to Magnoliales, the ancestor group of all the angiosperms, reveals a high conservation among dicot plants. On the contrary, the introns of both ancient and advanced monocot orders show relevant divergences represented by insertions and deletions in conserved specific regions of the introns. As a consequence of some of these rearrangements, a structure similar to a transposable element is generated in advanced monocots. This specific structure, common in all the analyzed species of Poales, seems to be generated by a stepwise process and it is not dependent on an insertion event.