Genome structure and apomixis in Phoenicaulis (Brassicaceae; Boechereae)

Apomixis in crucifer (Brassicaceae) species is rare, reported in just four genera (Boechera, Draba, Erysimum, and Parrya), and one intergeneric hybrid (Raphanobrassica). It is well studied only in Boechera, where it is widespread among 100+ recognized species. However, its occurrence in related gene...

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Bibliographic Details
Published in:Journal of systematics and evolution : JSE 2021-01, Vol.59 (1), p.83-92
Main Authors: Mandáková, Terezie, Ashby, Kaylynn, Price, Bo J., Windham, Michael D., Carman, John G., Lysak, Martin A.
Format: Article
Language:English
Subjects:
Apomixis
apospory
autopolyploidy
Boechera
Brassicaceae
Chromosomes
Diploids
Divergence
Fertility
Genomes
karyotype evolution
Karyotypes
Phoenicaulis
Populations
Rare species
Reproduction
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Summary:Apomixis in crucifer (Brassicaceae) species is rare, reported in just four genera (Boechera, Draba, Erysimum, and Parrya), and one intergeneric hybrid (Raphanobrassica). It is well studied only in Boechera, where it is widespread among 100+ recognized species. However, its occurrence in related genera of the tribe Boechereae has not been documented previously. Here we analyzed genome evolution, mode of reproduction, and fertility of the monospecific Boechereae genus Phoenicaulis (P. cheiranthoides), endemic to the northwestern United States. We discovered that the species encompasses diploid (2n = 2x = 14), triploid (2n = 3x = 21), and tetraploid (2n = 4x = 28) populations. Comparative chromosome painting analyses revealed that the three karyotypes are essentially structurally identical, differing only in the presence of a largely heterochromatic chromosome (Het) in the triploid and tetraploid cytotypes. The genome structure of Phoenicaulis appeared identical to that of Boechera species previously analyzed, suggesting genomic stasis despite the morphological and molecular divergence of the two genera. This genome colinearity extended to the presence and structure of the Het chromosomes, which are closely associated with apomictic reproduction in Boechera. Interestingly, all three cytotypes of Phoenicaulis proved to be apomictic, regardless of the presence or absence of a Het chromosome, and sexual populations have yet to be identified.
ISSN:1674-4918
1759-6831
DOI:10.1111/jse.12555