Abstract Detail

Chromosome and Karyotype Evolution in Plants

Burchardt, Paula [1].

Dynamics of karyotype evolution in holocentric Rhynchospora Vahl (Cyperaceae).

Cyperaceae comprises ca. 5000 species in ca. 102 genera. It is one of the four Angiosperm families that possess holocentric chromosomes. Holocentric chromosomes exhibit kinetochore activity along almost their entire length. This diffuse organization favors the occurrence of numerical chromosome variations since chromosome fragments resulting from fission are not necessarily lost in subsequent cell divisions. Rhynchospora, one of the genera of this family that has holocentric chromosomes, is composed of species whose karyotypes vary between 2n = 4 and 2n = 62. This variation is mainly attributed to polyploidy, but also to fission/fusion events that lead to dysploidies. To understand how karyotypic differentiation and evolution occurs in this genus, chromosome numbers, DNA content, and occurrence and distribution of CMA/DAPI heterochromatin considering the phylogenetic organization of Rhynchospora taxa were analyzed. Additionally, chromosome numbers and genome sizes from the literature for Rhynchospora were compiled. By increasing the number of taxa and populations studied, first chromosome counts for four taxa, new population counts for 13 taxa, and three new cytotypes in Rhynchospora globosa were observed, in addition to a new chromosome race in R. tenuis. As for DNA content, first reports for 17 taxa are presented. The genus is characterized by a great diversity among species since both genome sizes and chromosome numbers showed variation. However, DNA content variation is not always correlated with the chromosome number variation, indicating that, in addition to polyploidy, dysploidies are involved karyotype diversity. The accumulation and distribution of heterochromatin also differed greatly between species. In a phylogenetic analysis of these data, it was observed that related species are not necessarily cytogenetically similar, since numbers, genome sizes, and heterochromatin vary even within clades. Therefore, it is evident that this genus is tolerable of major structural changes. With these results, it became clear that increasing the sampling of species and populations in cytogenetic studies is very important to have a better understanding of the mechanisms that rule karyotypic evolution in Rhynchospora.

1 - Rua São Vicente, 548/311, Porto Alegre, RS, 90630-180, Brazil

Keywords:
DNA content
Dysploidy
Fission
Fusion
Heterochromatin
Holocentric chromosomes
polyploidy.

Presentation Type: Colloquium Presentations
Session: C11, Chromosome and Karyotype Evolution in Plants
Location: /
Date: Friday, July 23rd, 2021
Time: 12:30 PM(EDT)
Number: C11010
Abstract ID:102
Candidate for Awards:None