Showing papers on "Cestrum published in 2003"
TL;DR: Using slot-blot and fluorescent in situ hybridization (FISH), 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.
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.
106 citations
TL;DR: The data indicate that the A/T rich minisatellite might have evolved in response to the loss of Arabidopsis-type telomeres, and might indicate past recombination and chromosomal fusion events, processes that may have contributed to the large size of Cestrum chromosomes.
Abstract: The genus Cestrum in the Solanaceae family is unusual in lacking Arabidopsis-type telomeres (TTTAGGG)n, although short interstitial telomeric sequences (ITSs) occur scattered throughout the genome in both orientations. To isolate candidate telomeric sequences in Cestrum we assumed that some of the ITSs were residues of the original telomeres and that they may still be located in the vicinity of present-day telomeres. Three sequence types associated with ITSs were cloned and characterized; these were termed NA3G, BR23 and A/T-rich minisatellite. These high copy number sequences are dispersed across the genome and clustered at a number of chromosomal loci. Their association with ITSs, which can act as recombination hotspots, might indicate past recombination and chromosomal fusion events, processes that may have contributed to the large size of Cestrum chromosomes. The sequences are frequently arranged as NA3G-ITS-BR23 blocks embedded in an A/T-rich minisatellite array. The A/T-rich minisatellite is of particular interest because the consensus 5′-T4–5AGCAG-3′ might be a derivative of “typical” eukaryotic telomeric sequence motifs. The sequence is abundant at the end of some chromosomes in C. parqui and is found not only in Cestrum but also in the closely related genera Sessea and Vestia, which also lack Arabidopsis-type telomeric sequences. However, the sequence is absent from the Solanaceae genera investigated that are outside the group, including the closely related genus Streptosolen, which all have the Arabidopsis-type telomere. The data indicate that the A/T rich minisatellite might have evolved in response to the loss of Arabidopsis-type telomeres.
42 citations
TL;DR: Three basic pollen types were observed considering the ornamentation: perforate-scabraye, verrucate and striate, which may be useful to taxonomical identification of the studied species of Cestrum.
Abstract: This paper studied the pollen morphology of 12 species of Cestrum, C. amictum Schltdl., C. coriaceum Miers, C. laevigatum Schltdl., C. lanceolatum Schott ex Sendtn., C. martii Sendtn., C. megalophyllum Dunal, C. parqui L`Her., C. retrofractum Dunal, C. salzmannii Dunal, C. schlechtendahlii G. Don, C. sendtenerianum Mart. ex Sendtn and C. viminale Sendtn.. The studied specimen was collected in the hygrophilous forest of Bahia State. The polliniferous material was acetolyzed and the pollen grains were examined in light microscope. The pollen grains were medium sized, but their size range varied from 20,0 to 50,0µm, oblate spheroidal to subprolate 3-colporate. Three basic pollen types were observed considering the ornamentation: perforate-scabraye, verrucate and striate. These analyzed data may be useful to taxonomical identification of the studied species of Cestrum
8 citations
TL;DR: Identification keys, descriptions and illustrations of some species, besides the geographical distribution data, flowering and fruiting periods, are presented in this study.
Abstract: This paper consisted of the Cestrum taxon survey in south Higrophyllous Forest and extreme south of Bahia State, Brazil. 12 species were found: C. amictum Schltdl., C. coriaceum Miers, C. laevigatum Schltdl., C. lanceolatum Schott ex Sendtn, C. martii Sendtn, C. megalophyllum Dunal, C. parqui L`Her., C. retrofractum Dunal, C. salzmannii Dunal, C. schlechtendahlii G. Don, C. sendtenerianum Mart. ex Sendtn and C. viminale Sendtn. Identification keys, descriptions and illustrations of some species, besides the geographical distribution data, flowering and fruiting periods, are presented in this study
6 citations