Telomere sequence localization and karyotype evolution in higher plants

B chromosomes: a physiological enigma

“…A single B contains in the region of 300 Mb of DNA. In terms of molecular organization, the chive Bs lack Arabidopsis-like telomeric repeat sequences, and this is consistent with their origin from within the Alliaceae where the A chromosomes typically lack these sequences (Fuchs, Brandes & Schubert, 1995). The Bs also resemble specifically the A chromosomes of chives in the organisation of a 375 bp GC-rich dispersed satellite sequence (Barnes, James & Jamieson, 1985).…”

Numerical variations in species exhibiting holocentric chromosomes: a nomenclatural proposal

“…Possibly the same mutational event which results in the fragmentation of all the chromosomes may likewise give rise, in inverse form, to complete symploidy. The fusion or fission mechanism should occur in chromosomal regions specific and unique to each chromosome (MULLER et al 1991;FucHs et al 1995); otherwise the fusions and fissions would give rise to highly asymmetric karyotypes, which has not been observed to the present. These regions appear to have the capacity to redistribute themselves on the chromosome after each cycle of agmatoploidy or symploidy; if this were not the case, series like 12AL-24BL-48CL, observed in Luzula, would not be possible.…”

“…In recent years, numerous articles have appeared on species with holocentric chromosomes, presenting cytotaxonomic revisions (ScHMID 1982;CAYOUETTE andMoRISSET 1985a, 1985b;BROWN et al 1992;LucENO and CASTROVIEJO 1993), C-hand '·and fluorescence patterns (RAY and VENKETESWARAN 1978;GonAY and PIMPINELLI 1986;PANZERA et al 1992;, chromosome ultrastructure (BRASELTON 1981;RUFAS and GIMENEz MARTiN 1986;GonAY et al 1992), comparative studies of DNA quantity (SEN et al 1990), genomic "in situ" hybridization (Hosm et al 1994), telomere sequence localization (MULLER et al 1991, FucHs et al 1995, etc. Nonetheless, insufficient attention has been paid to the nomenclature of specific mechanisms of chromosomal numerical variation in species with holocentric chromosomes, for which we believe a review of currently utilized terminology is necessary.…”

Survey of Arabidopsis- and Human-type Telomere Repeats in Plants Using Fluorescence in situ Hybridisation

“…The human-type telomere repeat (TTAGGG) n is common in vertebrates (Meyne et al 1989), and it has also been reported in some protozoa and fungi (Blackburn and Gall, 1978, Blackburn and Challoner, 1984, Schechtman, 1990. In plants, the telomere repeat (TTTAGGG) n was isolated in Arabidopsis Ausubel 1988, Richards et al 1992), and this Arabidopsis-type repeat has been reported in many angiosperms and gymnosperms (Ganal et al 1991, Broun et al 1992, Cox et al 1993, Biessmann and Mason 1994, Fuchs et al 1995, Wellinger and Sen 1997, Hizume et al 1998. Allium cepa and A. fistulosum possess unique terminal repetitive sequences and/or rDNA sequences in place of the typical telomere sequence (Pich et al 1996, Pich andSchubert 1998), and the absence of Arabidopsis-type telomere repeats were reported in other Asparagales (Adams et al 2000(Adams et al , 2001.…”