A Combination of the "Squash" and "Splash" Techniques to Obtain the Karyotype and Assess Meiotic Behavior of Prosopis laevigata L. (Fabaceae: Mimosoideae).

Abstract

A combination of modified squash and splash techniques was used for a cytogenetic study of mitotic and meiotic cells of Prosopis laevigata. The mitotic karyotype was obtained for the species, and meiotic behavior was monitored from prophase I through the synaptonemal complex (SC). Analysis using light microscopy showed 2n=28, with chromosomes that, depending on the technique employed, varied in length from 0.84 to 1.84 pm in squashed specimens and from 1.0 to 1.82 pm in splashed specimens. These values are larger than those previously recorded for other South American species of the genus. The karyotype was studied by the splash method. The frequency of tetraploid cells was about 11% of 2052 metaphase cells examined. Meiosis was normal, because 14 bivalents were seen at metaphase I. The SC in pachytene showed regular features and an asynchronous pairing pattern with some short segments of lateral elements apically or interstitially unpaired, and occasional partner exchanges between three lateral elements. A constant association of the telomeric end of a bivalent with the nucleolus in mid-and late-prophase suggests the location of an active nucleolus organizer region (NOR) and its relation with a unique pair of mitotic chromosomes with satellites. The techniques employed here are recommended for species not amenable to cytogenetic studies with conventional techniques.

Differential Amphiplasty and Nucleolar Dominance in Somatic Metaphase Cells as Evidence of Hybridization in <i>Prosopis juliflora</i> (Leguminosae, Mimosoideae)

“…The results show that both nucleolar dominances, the frequently observed suppression of nucleolus formation, and differential amphiplasty, that is, the retraction of secondary constrictions and associated satellites, are manifested in P. juliflora cells and that the polyploid condition induces changes that affect all chromosomes. The latter is manifested in a notable reduction in the size of the chromosomes since P. juliflora exhibits the lowest MC (1.01 µm) among the species of the genus in which this cytogenetic parameter has been recorded (Hunziker et al 1986, Tapia-Pastrana andMercado-Ruaro 2001) and this is consistent with the amphiplasty described in a series of karyological investigations in interspecific hybrids of Crepis (Navashin 1928(Navashin , 1934.…”

“…Although there is agreement about the basic number and the diploid condition of most species of the genus Prosopis, few cytogenetic studies have been able to establish karyotype formulas due mainly to the small size of the chromosomes, which ranges from 0.5 to 1.3 µm (Hunziker et al 1986). However, in populations of P. laevigata (Tapia Pastrana et al 1999, Tapia-Pastrana andMercado-Ruaro 2001), karyotype formulas were determined and two SAT chromosomes were identified. On this basis, a similar condition could be expected for the remaining species in Algarobia.…”

New Cytogenetic Information of Two Mexican Populations of Crotalaria incana L. (Leguminosae-Papilionoideae)

“…Although these evidences could suggest the existence of new cytotypes of Crotalaria incana, we prefer not to interpret them as such. It is convenient to mention that the splash method used in this study reduces the risks of damage to the chromosome structure and allows the chromosomes to expand softly in the cytoplasm with absolute freedom, making it possible to observe all the details and fine aspects of their architecture in prometaphase and typical metaphase, especially the presence of secondary constrictions and satellites (Tapia-Pastrana and Mercado-Ruaro 2001, Tapia-Pastrana et al 2002, Gómez-Acevedo and Tapia-Pastrana 2003. Secondary constrictions may be viewed as a state of arrest of condensation of the regions bearing the nucleoli at prophase, and treated as chromosomal markers of active NORs (Bush and Smetana 1970), although it is more likely that the uncoilings which are similar to secondary constrictions described in this paper, represent chromatin segments of unknown nature, lacking active NORs, as the nuclei in interphase and prophase seen during the progress of this study did not show evidence of variable numbers of nucleoli, collective nucleolus, nucleolar fusion or chromatinic thickenings, as is typical of superior plants whose complements include several active NOR sites (Stack 1974, Golczyk andJoachimiak 2003).…”

Cytogenetics Analysis in Somatic Cells of <i>Dermatophyllum secundiflorum</i> (Mescal Bean) Reveals Satellite Association on Subtelocentric Chromosomes

“…However, in Leguminosae, the description of karyotypes where the sm or st chromosomes carry secondary constrictions associated with satellites on their short arms is increasingly frequent (Tapia-Pastrana and Mercado-Ruaro 2001, Gómez-Acevedo and Tapia-Pastrana 2003, Tapia-Pastrana and Gómez-Acevedo 2005, Biondo et al 2006. In particular, the detailed description of the SAT chromosomes in D. secundiflorum should consider that some metaphase plates revealed that what appears as a single secondary constriction and satellite results from the fusion of such structures present in sister chromatids (Fig.…”