Inter-telomeric connections and achiasmate meiosis in Tradescantia spathacea Sw.

Abstract

While demonstrating chromosome ring and chain configurations formed during meiosis I of permanent translocation heterozygote Tradescantia spathacea Sw. (syn. Rhoeo spathacea; 2n = 2x = 12) to a group of students, two different patterns of chromosome behavior were observed for the first time in various buds of this plant. While in some buds meiosis was characterized by the presence of chain multiples of varying lengths with chromosomes in each configuration joined exclusively by terminal chiasmata, meiosis in the other set of buds was conspicuous in that the chain configurations, wherever observed, did not have any chiasmata. The achiasmate chromosomes were held in chain configurations exclusively by thin inter-telomeric connections which occasionally span the whole cell. These connections were prominent at early prophase stage and by the time meiotic stage progressed to diplotene the connections had disappeared leaving all the 12 chromosomes scattered at diplotene and the ensuing meiotic stages. The behavior of chromosomes was typical of a desynaptic-mutant. The anaphase I was highly erratic and in 96.70 % cells 1-6 lagging chromosomes were observed which later appeared as micronuclei in 58.90 % cells. It is proposed that some alteration in the cellular microenvironment probably altered the telomeric architecture that not only impeded the chiasmata formation but also induced ectopic pairing through inter-telomeric connections.

Is partial desynapsis in cauliflower (Brassica oleracea L. var. botrytis) pollen mother cells linked to aneuploidy in the crop?

“…Higgins et al (2011) elucidated that the RecQ helicase AtRECQ4 in Arabidopsis is required for normal levels of fertility, by dissolving recombination intermediates between non-self telomeres during meiosis, and its absence leads to chromatin bridges and chromosome fragmentation in a small number of cells. Koul and Nagpal (2016) observed inter-telomeric connections in an achiasmatic meiosis in Tradescantia spathacea, in which the connections were prominent at early stages but disappeared at the time of diplotene. It was proposed that alteration in the cellular microenvironment may have altered the telomeric architecture that not only impeded the chiasmata formation but also induced ectopic pairing through inter-telomeric connections.…”