How diploidization turned a tetraploid into a pseudotriploi

Terezie Mandáková, Andrew D. Gloss, Noah K. Whiteman, Martin A. Lysak

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

PREMISE OF THE STUDY: Despite being highly fertile and occupying a large geographic region, the North American heartleaf bittercress (Cardamine cordifolia; Brassicaceae) has a puzzling triploid-like chromosome number (2 n = 3 x = 24). As most triploids are sterile, we embarked on a detailed analysis of the C. cordifolia genome to elucidate its origin and structure. METHODS: Mitotic and meiotic chromosome complement of C. cordifolia was analyzed by comparative chromosome painting using chromosome-specifi c BAC contigs of Arabidopsis thaliana. Resulting chromosome patterns were documented by multicolor fl uorescence microscopy and compared with known ancestral and extant Brassicaceae genomes. KEY RESULTS: We discovered that C. cordifolia is not a triploid hybrid but a diploidized tetraploid with the prevalence of regular, diploid-like meiotic pairing. The ancestral tetraploid chromosome number (2 n = 32) was reduced to a triploid-like number (2 n = 24) through four terminal chromosome translocations. CONCLUSIONS: The structure of the pseudotriploid C. cordifolia genome results from a stepwise diploidization process after whole-genome duplication. We showed that translocation-based descending dysploidy (from n = 16 to n = 12) was mediated by the formation of fi ve new chromosomes. The genome of C. cordifolia represents the diploidization process in statu nascendi and provides valuable insights into mechanisms of postpolyploidy rediploidization in land plants. Our data further suggest that chromosome number alone does not need to be a reliable proxy of species’ evolutionary past and that the same chromosome number may originate either by polyploidization (hybridization) or due to descending dysploidy.

Original languageEnglish (US)
Pages (from-to)1187-1196
Number of pages10
JournalAmerican journal of botany
Volume103
Issue number7
DOIs
StatePublished - Jul 2016

Keywords

  • Brassicaceae
  • Centromere loss
  • Chromosome fusion
  • Chromosome translocation
  • Diploidization
  • Dysploidy
  • Karyotype evolution
  • Polyploidy
  • Whole-genome duplication

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Plant Science

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