Abstract Detail



Functional Genetics/Genomics

GarcĂ­a, Miguel [1], Costea, Mihai [2], Ibiapino, Amalia [3], Stefanovic, Sasa [4], Guerra Filho, Marcelo [5].

Genome size and karyotype evolution in Cuscuta (Convolvulaceae).

Cuscuta (dodder) is one of the most diverse groups of obligate parasitic plants comprising about 200 species, many of which have a substantial economic and ecological importance.  Systematics of the genus has been challenging in the past because of rampant hybridization the lack of morphological characters, but several recent molecular studies have provided an explicit and robust phylogenetic framework for this group.  Albeit limited, the currently available evidence indicates that Cuscuta may represent a genus with the broadest karyotypic and genome size diversity among all of angiosperms.  First, it includes species not only with regular monocentric but also with holocentric chromosomes, a feature found in a very few phylogenetically scattered groups of plants.  Also, dodders exhibit significant karyotype variation, with reported chromosome numbers varying from 2n = 8 to 2n = 60.  In addition, the genus is diverse in chromosome size, symmetrical or asymmetrical karyotypes, and a high variation in nuclear DNA content.  The aim of this study is to further explore the limits of karyotype diversity in Cuscuta as a step towards a greater understanding of the chromosome evolution and polyploidy across this genus.  Twenty-five new collections were analyzed using iron hematoxylin or DAPI staining.  Quantification of genome size in twelve of these species was also performed using flow cytometry.  These results, along with tractable results from previous cytological studies in the genus, are presented in a phylogenetic context.  Karyotype diversity in Cuscuta is much more extensive than previously thought.  We report for the first time 2n = 90 (hexaploid) and ~150 (decaploid) chromosome numbers in the genus.  The nuclear DNA content variation in the species examined was over 65-fold, which, along with previously available estimates, makes Cuscuta one of the most diverse angiosperm genus in terms of genome size.  Hybridization and polyploidy have likely played a significant role in Cuscuta species diversification.  The enormous variation in chromosome type, number, size, and DNA amounts, along with a well-resolved phylogeny at multiple levels, makes Cuscuta a great model to study genome and chromosome evolution in plants generally, and the transition from monocentric to holocentric chromosomes in particular.


1 - University of Toronto Mississauga, Biology, 3359 Mississauga Rd, Mississauga, ON, L5L1C6, Canada
2 - 75 University Avenue West, Waterloo, Ontario, ON, N2L3C5, Canada
3 - Federal University of Pernambuco, Botany, Receife, PE, Brazil
4 - University Of Toronto Mississauga, Department Of Biology, 3359 Mississauga Rd, Mississauga, ON, L5L 1C6, Canada
5 - Av Flor De Santana , 263/1502, Casa Forte, Recife, PE, 50060-280, Brazil

Keywords:
none specified

Presentation Type: Oral Paper
Number: 0007
Abstract ID:377
Candidate for Awards:None


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