First genome size assessment and fluorochrome chromosome banding in Argania spinosa (L.) Skeels (Sapotaceae)

ABSTRACT

Argania is a monotypic genus belonging to the family Sapotaceae and comprising the only species Argania spinosa. This taxon, endemic to southern Morocco (northern Africa), is important in arid lands. It has a high pastoral value, numerous traditional uses, and it is an important industrial crop for food and cosmetics. A few chromosome counts are available for the species but to date, there is no information on its genome size. Apart from being a parameter useful in many aspects of plant systematic and evolutionary biology, knowing the nuclear DNA amount is a pre-requisite to any genome-sequencing program. In this paper, we present for the first time data on the nuclear DNA content in Argania spinosa, from two populations, and we confirm its chromosome number. Genome size was estimated as 2C = 1.48 pg (1C = 723.72 Mbp) in both studied accessions, revealing a small genome. The chromosome count (2n = 20) revealed that the species has the lowest basic chromosome number (x = 10) in the Sapotaceae, and suggests a descending dysploidy process in the family. The first morphological characterisation of Argania spinosa’s karyotype is presented here. In addition, fluorochrome banding, performed with chromomycin A₃ and DAPI, showed the absence of AT-rich regions and the presence of GC-rich regions located in three chromosome pairs, bringing the first molecular cytogenetic data in the genus.

KEYWORDS:

• Argania spinosa
• chromomycin A₃
• chromosome number
• DAPI
• flow cytometry
• fluorochrome banding
• genome size
• heterochromatin

Acknowledgments

We thank Josep M. Montserrat, who facilitated the plant collection in Barcelona’s Botanic Garden, Chari González (Centres Científics i Tecnològics, Universitat de Barcelona) for her assistance in genome size estimation, and Oriane Hidalgo (Institut Botànic de Barcelona) for Figure 1 elaboration.

Author contributions

MKH proposed and initiated this research, which, after her death, the other authors have continued and finished. The other authors have participated in the following tasks: YB, plant collection and genome size assessment. JV, plant collection and herbarium voucher preparation. TG and JV, genome size assessment. SSY, TG and JV, cytogenetics. SSY, chromosomal image obtention and figure elaboration. JV, first manuscript draft production. All the authors have read, in several turns, and approved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author.

Data availability statement

All data are directly presented in the paper.

Additional information

Funding

This work has been supported by the Catalan government (project 2021SGR00315).