Firenze University Press Caryologia www.fupress.com/caryologia International Journal of Cytology, Cytosystematics and Cytogenetics Chromosome number and genome size diversity in five Solanaceae genera Citation: A. Teixeira Mesquita, M.V. Romero-da Cruz, A.L. Sousa Azevedo, E.R. Forni-Martins (2019) Chromo- some number and genome size diver- Amanda Teixeira Mesquita1,*, Marìa Victoria Romero-da Cruz1, Ana sity in five Solanaceae genera. Caryo- Luisa Sousa Azevedo2, Eliana Regina Forni-Martins1 logia 72(3): 105-115. doi: 10.13128/ caryologia-772 1 Departamento de Biologia Vegetal, Universidade Estadual de Campinas, Rua Monteiro Lobato 255, CEP: 13.083-970 Campinas (SP), Brasil Published: December 13, 2019 2 Embrapa Gado de Leite, Empresa Brasileira de Pesquisa Agropecuária (Embrapa), Rua Copyright: © 2019 A. Teixeira Mesqui- Eugênio do Nascimento 610, CEP: 36.038-330 Juiz de Fora (MG), Brasil ta, M.V. Romero da Cruz, A.L. Sousa *Corresponding author: [email protected] Azevedo, E.R. Forni Martins. This is an open access, peer-reviewed article published by Firenze University Press Abstract. Sixteen species of Solanaceae, belonging to five genera, were studied karyo- (http://www.fupress.com/caryologia) logically through chromosome counting, chromosomal measurement, and karyotype and distributed under the terms of the symmetry. Genome size (GS) estimation was performed on fifteen species using flow Creative Commons Attribution License, cytometry. The chromosome number 2n=24 was found in all Solanum species and which permits unrestricted use, distri- Acnistus arborescens, 2n=22 was found in Brunfelsia uniflora, and 2n=16 in Cestrum bution, and reproduction in any medi- representatives. Physalis pubescens was the only specie with evidence of polyploidy, um, provided the original author and showing 2n=4x=48 chromosomes. The chromosome numbers of S. adspersum, S. inodo- source are credited. rum, S. flaccidum, S. sanctae-catharinae, and B. uniflora were reported for the first time. Data Availability Statement: All rel- Haploid karyotype length (HKL) was statistically different between the studied species. evant data are within the paper and its The polyploid P. pubescens showed the largest HKL value, 93.10 µm. In general, kary- Supporting Information files. otypes were symmetrical with predominance of metacentric chromosomes. Chromo- some size was small in most species (<4 µm), while S. diploconos, C. laevigatum, and Competing Interests: The Author(s) C. mariquitense, species with high HKL values, exhibited larger chromosomes. Genome declare(s) no conflict of interest. size estimation were unpublished for ten studied species and were the first estimation for the genera Acnistus, Brunfelsia and Physalis. Were observed about eight-fold differ- ences between species with averages varying from 2C=2.57 pg to 2C=20.27 pg. As both HKL and GS showed a continuous variation. We observed partial similarity in the spe- cies ordered according to HKL and GS. The Solanaceae genera showed a constant chro- mosome number and a tendency to posse symmetrical karyotypes. The genome size also showed differences, which suggests that chromosome evolution in the group could be driven by alterations in the repetitive fractions of the genome. Keywords. Acnistus, Brunfelsia, Cestrum, Physalis, Solanum, karyotype evolution. INTRODUCTION The Solanaceae family comprises about 2,500 species and 100 genera and have cosmopolitan distribution. The greatest diversity of the family is found in Neotropical regions (D’Arcy 1991; Hunziker 2001). Members of Solanace- ae have great ecological and morphological diversity, characteristics which favoured the occupation of diverse habitats, such as desert regions, tropi- Caryologia. International Journal of Cytology, Cytosystematics and Cytogenetics 72(3): 105-115, 2019 ISSN 0008-7114 (print) | ISSN 2165-5391 (online) | DOI: 10.13128/caryologia-772 106 Amanda Teixeira Mesquita et al. cal rainforests, and even disturbed areas (D’Arcy 1991; Only about 8% of Solanaceae taxa have available GS Knapp 2002). data. This character has more variability than chromo- The family includes several species of important some number (Soltis et al. 2003). In Solanum, the GS global food crops with high economic value, such as ranges of from forty-fold in species with 2n=24 chromo- tomatoes (Solanum lycopersicum), potatoes (Solanum somes. The smallest reported C-value is in S. chacoense, tuberosum), eggplants (Solanum melongena), and chilli 1C=0.63 pg (Bennett and Smith 1976), while the largest peppers (Capsicum spp.), widely used drug plants, such value is 1C= 24.80 pg, found in S. hartwegii (Pringle and as tobacco (Nicotiana tabacum), “datura” (Datura stra- Murray 1991). monium), and “angel’s tears” Brugmansia suaveolens, as Nevertheless, there are still many gaps in karyotypic well as many ornamental plants, such as species of the knowledge for the Solanaceae family and such informa- genus Brunfelsia, Cestrum and Petunia. Many Solan- tion (i.e. genome size, chromosome number, and kar- aceae species, including tomatoes, potatoes, and tobacco, yotype variables) is important to complete current data are model organisms for various biological studies, and and to better understand the systematic relationships their genomes are some of the most well studied among and chromosome evolution of the family. Therefore, the angiosperms (Knapp et al. 2004). objectives of this study were: (1) to report original chro- Karyotype information about species and groups mosome numbers and describe the karyotype variables are important for taxonomic and evolutionary stud- in distinct genera of the Solanaceae family, (2) to deter- ies, whereas karyological changes accompany specia- mine the genome size (GS) using flow cytometry for the tion and, consequently, the diversification of the groups first time for many species. (Guerra et al. 2008, 2012, Chiarini et al. 2018). The chro- mosome number, nuclear DNA content, total length of the chromosome complement, asymmetry indices, and MATERIAL AND METHODS number and location of the rDNA sites and heterochro- matic bands are the main data used in cytotaxonomic Plant material studies. Chromosome number data is the most available information and is not influenced by external agents, Sixteen species from the genera Acnistus, Brunfelsia, such as age of individuals, environmental conditions, Cestrum, Solanum, and Physalis were collected in South- and gene expression, providing accurate data about spe- eastern Brazil. Voucher specimens were deposited into cies evolution (Dobginy et al. 2004, Guerra et al. 2008, the Herbarium at the University of Campinas (UEC). 2012). Cytogenetic characterization, accompanied by a Data collection is detailed in Table 1. genome size (GS) study, can offer important informa- tion about genome organization, phylogenetic relation- Chromosome preparations ships, and evolutionary trends. This approach has been successful used in some Solanaceae (Mishiba et al. 2000, Seeds of at least three individuals per species were Moscone 2003, Chiarini et al. 2014). germinated in Petri dishes. In some cases, 1 ml gibberel- Chromosome data is available for some genera of lic acid (GA3) was applied to break seed dormancy (Ellis Solanaceae, while for other genera there is not enough et al. 1985). According to previous tests, root meristems data or information about their chromosomes. Lycium were pre-treated with different solutions to block the cell and Solanum present constant chromosome number cycle to obtain good chromosome spread and condensa- (2n=24 and polyploids) (Bernadello and Anderson 1990; tion (Table 2). The root apices were fixed in 3:1 ethanol: Bernadello et al. 1994; Chiarini and Bernadello 2006; acetic acid (v:v) mixture that was stirred for a minimum Rego et al. 2009; Stiefkens et al. 2010; Melo et al. 2011; of 12 h at room temperature (RT) and stored at -6ºC Chiarini et al. 2014), while Capsicum shows 2n=24 and until slide preparation. Slides were made using root mer- 2n=26 (Moscone 1993; Moscone et al. 2007; Aguilera et istems that were previously digested in a solution of 1% al. 2014; Grabiele et al. 2014; Romero-da Cruz and For- macerozima, 2% cellulase, and 20% pectinase for 10-15 ni-Martins 2015; Romero-da Cruz et al. 2017). For the minutes at 37ºC and squashed in a drop of 45% acetic Cestreae tribe, composed of Cestrum, Sessea, and Vestia, acid. Coverslips were removed after freezing in liquid the only chromosome number reported to date is 2n=16 nitrogen for 15 minutes. The cells were photographed (Fregonezi et al. 2006; Las Peñas et al. 2006; Fernandes under a microscope Olympus BX51 with a DP72 camera et al. 2009; Urdampilleta et al. 2015). The greatest range attached and images were captured using Olympus DP2 in chromosome number is found in Nicotiana (n=12 to BSW program (Olympus Corporation). n=32, and polyploids, Chase et al. 2003). Chromosome number and genome size diversity in five Solanaceae genera 107 Table 1. Cytogenetics data of Solanaceae species: Species and voucher specimen; provenance of materials; chromosome number, haploid karyotype formula (HKF), median haploid karyotype length (HKL), variation in chromosome length (VCL); symmetry indices A1 and A2; median DNA content (2C values). HKL – µm 2C values – pg Species (Voucher specimen) Provenance 2n HKF VCL – µm A1 A2 (CI) (CI) Acnistus arborescens Schltdl. Brazil: Rio Grande do Sul; Aratinga 24 12m 45.93 (2.78) 3.17-4.38 0.17 0.10 6.56 (0.06) (Monge 2787) Brunfelsia. uniflora D. Don Brazil; São Paulo; Campinas 22 7m+4sm 50.51 (0.50) 3.89-5.37 0.32 0.10 6.58 (0.13) (Mesquita 15) Cestrum laevigatum Schltdl. Brazil; São Paulo; Campinas 16 6m+2sm 78.72 (2.96) 7.92-10.88 0.23 0.10 20.27 (0.43) (Mesquita 12) C. mariquitense Kunth (Mesquita Brazil; São Paulo; Campinas 16 7m+1sm 73.91 (6.38) 7.35-11.39 0.21 0.12 - 14) Physalis pubescens L. (Vasconcellos Brazil; São Paulo; Jundiaí 48 19m+5sm 93.10 (2.87) 1.43-2.80 0.32 0.18 12.98 (0.09) Neto 00-068) Solanum Cyphomandra clade Solanum diploconos (Mart.) Bohs Brazil; São Paulo; Jundiaí 24 8m+4sm 74.72 (1.86) 4.63-7.49 0.32 0.14 19.22 (0.43) (Mesquita 23) Dulcamaroid clade S.