Abstract:

MADS-box genes encode a family of transcription factors. In angiosperms, MADS-box genes play key roles in vegetative growth and reproductive development, and are indispensable for the formation of inflorescences, flowers and fruits. To understand the evolution of MADS-box genes on a relatively small time scale, we conducted comparative genomic studies of a pair of closely related plant species, Arabidopsis thaliana and A. lyrata. A total of 106 and 115 MADS-box genes were identified from the two species, respectively, and phylogenetic analyses suggested that these genes correspond to Types I and II MADS-box genes. Type I genes have been duplicated and lost extensively in the lineages leading to the two species, whereas the number of Type II genes has not changed very much during the same period. Comparisons of the locations of orthologous gene pairs not only detected chromosomal regions that showed clear microsynteny between the two genomes, but also found evidence that most newly gained genes were generated through tandem and dispersed duplications rather than segmental duplication. Molecular evolutionary studies further suggested that different clades of MADS-box genes have experienced significantly different patterns of evolution, with functional constraints being less stringent for Type I genes than for Type II genes. Our results will help better understand the genetic differences between closely related species, and stimulate additional studies on the mechanisms that underlie speciation and biodiversification.

Key words: Arabidopsis thaliana, A. lyrata, MADS-box gene, copy number variation, evolutionary rate