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Pizzaia D, Oliveira-Maekawa VM, Martins AR, Mondin M, Aguiar-Perecin MLR. Karyotype structure and NOR activity in Brazilian Smilax Linnaeus, 1753 species (Smilacaceae). Comp Cytogenet 2019; 13:245-263. [PMID: 31528267 PMCID: PMC6715645 DOI: 10.3897/compcytogen.v13i3.35775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 07/05/2019] [Indexed: 06/10/2023]
Abstract
The genus Smilax Linnaeus, 1753 (Smilacaceae) is a large genus of dioecious plants distributed in tropical, subtropical and temperate regions. Some Smilax species have medicinal importance and their identification is important for the control of raw material used in the manufacture of phytotherapeutical products. The karyotypes of seven Brazilian Smilax species were investigated. Mitotic metaphases of roots from young plants were analysed in Feulgen-stained preparations. The karyotypes were asymmetric and modal with 2n = 2x = 32 chromosomes gradually decreasing in size. In S. goyazana A De Candolle & C De Candolle, 1878, a polyploid species, 2n = 4x = 64. In all the species, the large and medium-sized chromosomes were subtelocentric and submetacentric and the small chromosomes were submetacentric or metacentric. Their karyotypes were quite similar, with differences in the arm ratio of some chromosomes. S. fluminensis Steudel, 1841 differed from the other species by having a large metacentric chromosome 1. These findings suggest that evolution occurred without drastic changes in the chromosomal structure in the species analyzed. Terminal secondary constrictions were visualized on the short arm of some chromosomes, but they were detected only in one homologue of each pair. Due to the terminal location and the degree of chromosome condensation, secondary constrictions were not visualized in some species. The nucleolus organizer regions (NORs) were mapped by silver-staining and fluorescent in situ hybridization (FISH) in S. rufescens Grisebach, 1842 and S. fluminensis. Silver-staining and FISH signals were colocalized on the short arms of six chromosomes in S. rufescens and four chromosomes in S. fluminensis. In FISH preparations, one of the largest chromosomes had the secondary constrictions highly decondensed in some cells. This finding and the heteromorphism observed in Feulgen-stained chromosomes suggest that differential rRNA gene expression between homologous rDNA loci can occur in some cells, resulting in different degrees of ribosomal chromatin decondensation. The presence of a heteromorphic chromosome pair in S. rufescens, S. polyantha Grisebach, 1842 and S. goyazana suggests a chromosomal sex determination in these dioecious species.
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Affiliation(s)
- Daniel Pizzaia
- Department of Genetics, Luiz de Queiroz College of Agriculture, ESALQ, University of São Paulo, Avenida Pádua Dias, 11, 13418-900 Piracicaba, SP, Brazil
| | - Vanessa M Oliveira-Maekawa
- Department of Plant Biology, The University of Campinas, UNICAMP, Barão Geraldo, 13083-970, Campinas, SP, Brazil
| | - Aline R Martins
- Department of Biological Sciences, Luiz de Queiroz College of Agriculture, ESALQ, University of São Paulo, Avenida Pádua Dias,11 13418-900, Piracicaba, SP, Brazil
| | - Mateus Mondin
- Department of Genetics, Luiz de Queiroz College of Agriculture, ESALQ, University of São Paulo, Avenida Pádua Dias, 11, 13418-900 Piracicaba, SP, Brazil
| | - Margarida L R Aguiar-Perecin
- Department of Genetics, Luiz de Queiroz College of Agriculture, ESALQ, University of São Paulo, Avenida Pádua Dias, 11, 13418-900 Piracicaba, SP, Brazil
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