Cestrum

Abstract: Using slot-blot and fluorescent in situ hybridization (FISH), we found no evidence for the presence of the Arabidopsis-type telomeric sequence (TTTAGGG)n at the chromosome termini in any of the Cestrum species we investigated. Probing for the human-type telomere (TTAGGG)n also revealed no signal. However, polymerase chain reaction experiments indicated that there are short lengths of the sequence TTTAGGG dispersed in the genome but that these sequences are almost certainly too short to act as functional telomeres even if they were at the chromosome termini. An analysis of related genera Vestia and Sessea indicates that they too lack the Arabidopsis-type telomere, and the sequences were lost in the common ancestor of these genera. We found that the Cestrum species investigated had particularly large mean chromosome sizes. We discuss whether this is a consequence of alternative telomere end maintenance systems.

Abstract: The genera Browallia, Cestrum, Hunzikeria, Leptoglossis, Nicotiana, Nierembergia, Petunia, Reyesia, and Salpiglossis, all members of the mainly Neotropical tribe Cestreae of the Solanaceae, are reviewed and generic lines are discussed. Hunzikeria, Leptoglossis, Reyesia, and Salpiglossis are given extensive attention, and a new species of Hunzikeria is described. Bouchetia is placed into synonymy under Salpiglossis. An evolutionary path from primitive ancestors to modern, advanced members of the group is postulated. Several genera of Solanaceae in tribe Cestreae have long been subject to confusion, and this paper suggests resolution of some of the problems. The names Bouchetia, Browallia, Cestrum, Hunzikeria, Leptoglossis, Nicotiana, Nierembergia, Petunia, Reyesia, and Salpiglossis are reviewed. The plants are mostly herbs or diminutive shrubs, and they occur in North and South America, some genera being disjunct. Although the study has spanned five years, this paper must be regarded as a report of unconcluded work rather than a completed investigation. Few living plants were seen and the herbarium survey was not exhaustive. In particular, species limits require definition. As the early emphasis was on North American species, these species receive more detailed treatment than those of South America.

Abstract: 1. Low temperature treatment reveals allocyclic segments in Fritillaria recurva (n=12), Tulbaghia pulchella (n=6), and in six species of Cestrum (n=8). These segments, which are underspiralised at mitotic metaphase, correspond to the interphase chromocentres and to the precociously condensed segments at pachytene. 2. The chromosomes of F. recurva contain H-segments in 11 of the 12 pairs. The patterns reveal heterogeneity in 10 of these in the 3 individuals considered, which were heterozygous for 8, 7 and 6 chromosome pairs. The close relationship of F. recurva, F. lanceolata and F. falcata is reflected in the parallel polymorphism of the heterochromatin patterns. 3. The plant of T. pulchella was heterozygous for the H-pattern in 5 pairs of chromosomes. The sixth, the nucleolar chromosome, contained no heterochromatin. The H-pattern was the same in the tetraploid cells which formed up to 80% of all divisions in lateral roots. 4. H-segments were present in 7 pairs in Cestrum elegans, and all 8 pairs in C. parqui and an unidentified Cestrum species. These plants were heterozygous for 4, 1 and 3 pairs respectively. No clear parallel polymorphism was detected in the H-patterns, but single chromosomes showed similarities. An attempt to induce differential contraction by means of chloramphenicol was unsuccessful, the effect being to produce colchicine-type metaphases. 5. Tulbaghia alliacea (n=6) and Hyacinthus litwinowii (n=9), newly described, are both heterozygous for a single segment with a previously unknown type of allocycly. This segment is normally uncontracted throughout the mitotic cycle and becomes fully spiralised only during division after the inhibition of anaphase by low temperature or chemical treatment. This segment is attached terminally to the secondary constriction of only one of the nucleolar chromosomes in each plant. 6. In Fritillaria the segments are mostly proximal and the chromocentres fuse to a considerable extent. In Tulbaghia the segments are terminal and there is little chromocentre fusion. Cestrum elegans, with segments dispersed along the chromosomes, is intermediate in this respect. Fusion appears to be controlled by the proximity in the telophase nucleus, in turn influenced by the position of the segments in the chromosomes. 7. In Fritillaria, Cestrum and Tulbaghia all or most chiasmata are formed near to the centromere. In Fritillaria and Cestrum, where this distribution overlaps that of the heterochromatin, the H-segments are interrupted by small regions of euchromatin. In Tulbaghia, where heterochromatin and chiasmata are localised at opposite ends of the chromosome arms, the segments are entire. It is suggested that crossingover in adjacent euchromatin causes small rearrangements of H-segments. 8. Chromosome maps showing the distribution of H-segments reveal structural heterogeneity within the species and corresponding heterozygosity within the individuals. Heterogeneity of H-patterns involves variation in the size and position as well as the number of H-segments. The frequency of heterozygosity in an individual does not necessarily increase with the number of segments.

Abstract: We studied the karyotypes of four Brazilian Cestrum species (C. amictum, C. intermedium, C. sendtnerianum and C. strigilatum) using conventional Feulgen staining, C-Giemsa and C-CMA3/DAPI banding, induction of cold-sensitive regions (CSRs) and fluorescent in situ hybridization (FISH) with rDNA probes. We found that the karyotypes of all four species was 2n = 2x = 16, with, except for the eighth acrocentric pair, a predominance of meta- and submetacentric chromosomes and various heterochromatin classes. Heterochromatic types previously unreported in Cestrum as neutral C-CMA30/DAPI0 bands, CMA3+ bands not associated with NORs, and C-Giemsa/CSR/DAPI- bands were found. The heterochromatic blocks varied in size, number, position and composition. The 45S rDNA probe preferentially located in the terminal and subterminal regions of some chromosomes, while 5S rDNA appeared close to the centromere of the long arm of pair 8. These results suggest that karyotype differentiation can occur mainly due to changes in repetitive DNA, with little modification in the general composition of the conventionally stained karyotype.

Abstract: The flavopilosa group of species of Drosophila, subgenus Drosophila, was established for D. flavopilosa Frey and 13 other species from the Neotropical region (Wheeler et al., 1962). In Chile, the exclusive natural breeding and feeding sites of D. flavopilosa are the flowers of the solanaceous plant, Cestrum parqui L'Her. Recently, Dr. A. Hunter from the Los Andes University (Colombia) and the present author, found inside the flowers of another species of Cestrum (C. tomentosum Sandwith) near Bogota, larvae of two other species of the group (D. acroria and another form not yet determined). These observations suggest that the members of the group are mainly pollen feeders, and probably are associated with different species of Cestrun. Although up to now it has not been possible to breed D. flavopilosa under laboratory conditions, the analysis of larval samples collected directly in their natural breeding sites, has allowed the author to study the chromosomal structure of some Chilean populations of the fly (Brncic, 1962). These studies have demonstrated that the populations of D. flavopilosa are polymorphic for the gene arrangements in their chromosomes, and that the frequencies of certain heterokaryotypes vary according to the geographic regions. These studies have also shown that there is an altitudinal gradient in the distribution of some of these gene arrangements. Such an analysis was interesting for many reasons.