Localización de satélites y cromosomas NOR para la interpretación del cariotipo de Sesbania virgata (Papilionoideae, Sesbanieae) de dos poblaciones americanas

Abstract

<p><strong>Background</strong>: Cytogenetic studies in the genus <em>Sesbania</em> show lack of agreement among the researchers about the precise number and position of secondary constrictions and satellites as well as their relation to the organization of the nucleolus. The lack of this information makes it difficult to carry out reliable comparative cytogenetic studies and chromosome evolution in this genus.</p><p><strong>Questions</strong>: Where are the secondary constrictions and satellites located in the chromosomes of <em>Sesbania</em> <em>virgat</em>a? Do these regions actively participate in the nucleolar organization?</p><p><strong>Study species</strong>: <em>Sesbania virgate</em> (Cav.) Pers.</p><p><strong>Study site</strong>: Municipality of Tlacotalpan, Mexico and Province of Salta, Argentina.</p><p><strong>Methods</strong>: Surface spreading and air-drying technique was applied to obtain chromosomes in prometaphase and typical metaphase from radicular meristems.</p><p><strong>Results</strong>: Each population exhibited a different karyotype and only two secondary constrictions associated with microsatellites in the short arms of the smallest chromosome pair and not in long arms as was suggested by other authors. The inclusion of secondary constrictions and satellites in the nucleolus of cells in prometaphase allowed to corroborate their active participation in the formation of this one. This information was used to reevaluate the position of the nucleolar organizer regions "NOR´s".</p><strong>Conclusions</strong>: Our results agree with the predominant point of view on the location of the "NOR´s" in the short arms of plant species, particularly in legumes. In addition, given that the populations under study are geographically isolated, we suggest that an active process of speciation manifested in the two found cytotypes whose differences are attributed to changes in the proportion of arms of the satellite chromosomes is favored.

Cytogenetics of Diphysa americana (Mill.) M.Sousa (Leguminosae-Papilionoideae-dalbergioid clade), a rare species from the coast of Oaxaca, Mexico

“…The karyotypic formula proposed here (5m + 5sm) shows that in the dalbergioid chromosome complements obtained so far, chromosomes with a medium (m) or slightly displaced (sm) centromere predominate (Table 1), and therefore they are symmetric or slightly asymmetric karyotypes (Tapia-Pastrana et al 2020). Likewise, the presence of secondary constrictions associated with microsatellites in short arms of sm chromosomes (SAT chromosomes) corroborates a trend in plant species where secondary constrictions are located preferentially in short arms (Lima de Faria 1976;Lim et al 2001), particularly in legumes (Biondo et al 2006;Tapia-Pastrana 2012;Tapia-Pastrana and Tapia-Aguirre 2018;Tapia-Pastrana et al 2020). Likewise, their role in the organization of the nucleolus is evident since they were observed associated with it in prometaphase cells (Fig.…”

Patterns of chromosomal variation in Mexican species of Aeschynomene (Fabaceae, Papilionoideae) and their evolutionary and taxonomic implications

“…villosa to 43.11 in A. sensitiva). Furthermore, the number, size and position of secondary constrictions and satellites (SAT chromosomes) confirm the karyotypic heterogeneity in this group and its usefulness as markers for taxa even below the species level, particularly for those taxa difficult to define (Palomino and Vázquez 1991, Solís Neffa and Fernández 2002, Tapia-Pastrana and Tapia-Aguirre 2018. Its role in the organization of the nucleolus is obvious since secondary constrictions and satellites were often associated with projections of nucleolar material or even were observed immersed in a single nucleolus or in several small nucleoli, so here they are considered as nucleolar organizer regions (NORs).…”