Phylogeny, chromosome number and genome size evolution in Physarieae (Brassicaceae).
|Fakulta / Pracoviště MU|
|Popis||The Physarieae tribe (Brassicaceae or mustard family), predominately with a base chromosome number of x=8, exhibits a remarkable diversity of haploid chromosome number, thereby suggesting a dynamic rate of chromosomal change. The goal of this research was to study, in a molecular phylogenetic context, the evolution of chromosome number and genome size within the tribe. Our molecular phylogenetic studies were generated with three independent loci (chloroplast ndhF, nrDNA ITS, and LUMINIDEPENDENS 5-7 exons and 5, 6 introns). The results suggest that Physarieae is a monophyletic lineage closest related to the Halimolobeae tribe. Within the tribe, three monophyletic clades are recovered: The NDDLS clade including five genera (Nerisyrenia, Dithyrea, Dimorphocarpa, Lyrocarpa, and Synthlipsis), the Paysonia clade, and the Physaria clade. The phylogenetic findings further suggest that there was a 2-fold genome size expansion after the divergence of Physarieae from closely related tribes (2C = 0.873 vs. 0.47 pg). The genome size of Physarieae has fluctuated widely during the evolution of Physarieae, and both genome size expansion and contraction occurred repeatedly. Overall DNA contents of Physarieae ranged from 0.5 to 4.364 pg/2C. Between the three major lineages of Physarieae, the Physaria clade showed the largest genome size on average, a finding that is rather unexpected considering known patterns of variation in other Brassicaceae. In Physarieae no obvious correlation was found between changes in genome size and chromosome number.|