RDNA mapping, heterochromatin characterization and AT/GC content of Agapanthus africanus (L.) Hoffmanns (Agapanthaceae).

Aryane C Reis,Victória R Campos,Flávia R Souza,Ana Luiza Franco,Lyderson F Viccini,Saulo M Sousa,Cristiane Zorzatto

doi:10.1590/0001-3765201620150514

Aryane C Reis, Victória R Campos + Show 5 more

Open Access

https://doi.org/10.1590/0001-3765201620150514

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Abstract

Agapanthus (Agapanthaceae) has 10 species described. However, most taxonomists differ respect to this number because the great phenotypic plasticity of the species. The cytogenetic has been an important tool to aid the plant taxon identification, and to date, all taxa of Agapanthus L'Héritier studied cytologically, presented 2n = 30. Although the species possess large chromosomes, the group is karyologically little explored. This work aimed to increase the cytogenetic knowledge of Agapanthus africanus (L.) Hoffmanns by utilization of chromosome banding techniques with DAPI / CMA3 and Fluorescent in situ Hybridization (FISH). In addition, flow cytometry was used for determination of DNA content and the percentage of AT / GC nitrogenous bases. Plants studied showed 2n = 30 chromosomes, ranging from 4.34 - 8.55 µm, with the karyotype formulae (KF) = 10m + 5sm. Through FISH, one 45S rDNA signal was observed proximally to centromere of the chromosome 7, while for 5S rDNA sites we observed one signal proximally to centromere of chromosome 9. The 2C DNA content estimated for the species was 2C = 24.4 with 59% of AT and 41% of GC. Our data allowed important upgrade for biology and cytotaxonomy of Agapanthus africanus (L.) Hoffmanns.

Highlights

The genus Agapanthus L’Héritier (Agapantahceae) is a monocotyledonous, herbaceus and perennial plant group endemic to southern Africa, with ten species in which three are considered evergreen and seven deciduous plants (Leighton 1965)
In Agapanthus L’Héritier, all plants measured until the moment have the same chromosome number, 2n = 30 (Riley and Mukerjee 1960, Sharma and Mukhopadhyay 1963), with little differences only in chromosome length
No secondary constrictions were observed and absolute chromosome length ranged from 4.34 - 8.55 μm (Table I) while the relative chromosome length revealed that the largest chromosome represented around 9.46% of the genome size and the shortest one 4.80% (Table I)

Summary

Introduction

The genus Agapanthus L’Héritier (Agapantahceae) is a monocotyledonous, herbaceus and perennial plant group endemic to southern Africa, with ten species in which three are considered evergreen and seven deciduous plants (Leighton 1965). In Agapanthus L’Héritier, all plants measured until the moment have the same chromosome number, 2n = 30 (Riley and Mukerjee 1960, Sharma and Mukhopadhyay 1963), with little differences only in chromosome length. Since chromosome length can vary with condensation, this parameter in plastic plants, studied without another chromosome marker is not a good tract for detection of speciation. More detailed karyological studies are very important to increment the utilization of chromosome length like a parameter of species identification in Agapanthus L’Héritier. Some studies have shown that Agapanthus africanus (L.) Hoffmanns has an important antifungal potential against plant pathogens (Singh et al 2008, Tagegne et al 2008)

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