Evolution of the cox1 intron in Solanaceae

M. VIRGINIA SÁNCHEZ-PUERTA; CINTHIA C. ABBONA; SERGEI KUSHNIR; DANNY GEELEN; ERIC TEPE; LYNN BOHS; RICHARD OLMSTEAD ; JEFFREY D. PALMER

Gante-Bélgica

Congreso; Comparative & Regulatory Genomics in Plants; 2011

Department of Plant Systems Biology (VIB-Ghent University)

The most pervasive case of HGT among angiosperms involves an intron found in the mitochondrial gene cox1 (Adams et al. 1998; Cho et al. 1998; Cho and Palmer 1999; Sanchez-Puerta et al. 2008). The most comprehensive study of this intron from more than 600 angiosperms, revealed ca. 70 putative horizontal transfer events of this intron and implies hundreds if not thousands of intron transfers among the totality of the 250,000+ species of extant angiosperms (Sanchez-Puerta et al. 2008). Several predictions can be drawn from the aforementioned observations: a) given the frequency and dispersal of the cox1 intron among angiosperms, a species-rich family is likely to include intron-containing members; b) if so, and given the recency of most transfers, an increased taxon sampling within the family will lead to a fine interspersion of intron-containing and intron- and CCT-lacking taxa; c) introns from unrelated family members will be closely related to each other suggesting intrafamilial horizontal transfers. Here, we tested these predictions through a large-scale cox1 intron survey in the family Solanaceae. An extensive survey of the cox1 intron from 496 plants of the family Solanaceae revealed that the intron was present in two unrelated clades: Hyoscyameae and Mandragoreae, with several intronless taxa and clades interspersed among them. Exon and intron based phylogenies showed incongruent relationships, but all solanaceous introns were closely related. This work shows that all predictions regarding cox1 intron evolution in the family Solanaceae came true. Multiple lines of evidence lead us to strongly favor the hypothesis, in which the cox1 intron was acquired once from a non-solanaceous donor and then transferred once or twice within the family Solanaceae. Finding intron-containing members of the family Solanaceae could be highly relevant to understanding the mechanism of intron homing in plants. We propose to test the functionality of the intron-encoded endonuclease, assess rates of intron colonization, and measure lengths of exonic coconversion tracts that accompany intron insertion in cybrid plants obtained by protoplast fusion experiments of two (intron-containing and intron lacking) solanaceous taxa.