Breakage–fusion–bridge cycles and de novo telomere formation on broken chromosomes in maize callus cultures

• Published in: Genome Vol. 59; no. 6; pp. 367 - 378
• Main Authors: Santos-Serejo, Janay A, Aguiar-Perecin, Margarida L.R
• Format: Journal Article
• Language: English
• Published: Canada NRC Research Press 01.06.2016; Canadian Science Publishing NRC Research Press
• Subjects: breakage–fusion–bridge cycle; callus culture; Cell culture; Cell Cycle - genetics; Cells, Cultured; Chromosomal Instability; Chromosome Banding; Chromosome Breakage; Chromosomes; Chromosomes - genetics; Chromosomes - physiology; Corn; culture de cals; cycle de bris–fusion–pont; fluorescence in situ hybridization; Genetic aspects; Genomes; Heterochromatin; Heterochromatin - genetics; hybridation in situ en fluorescence; hétérochromatine; In Situ Hybridization, Fluorescence; maize; maïs; Meiosis - genetics; Mitosis - genetics; Observations; Physiological aspects; Telomerase; telomere; Telomere - genetics; Telomeres; télomère; Zea mays; Zea mays - genetics; fluorescence in situ hybridization; hybridation in situ en fluorescence; hétérochromatine; culture de cals; télomère; telomere; maïs; cycle de bris–fusion–pont; maize; callus culture; breakage–fusion–bridge cycle; heterochromatin
• ISSN: 0831-2796; 1480-3321
• DOI: 10.1139/gen-2015-0211

Breakpoints involved in chromosome alterations associated with heterochromatin have been detected in maize plants regenerated from callus culture. A cytogenetic analysis of plants regenerated from a maize callus was performed aiming to analyze the stability of a chromosome 7 bearing a deficiency-duplication (Df-Dp), which was interpreted as derived from a chromatid type breakage–fusion–bridge (BFB) cycle. The Df-Dp chromosome 7 was stable in mitotic and meiotic cells of the regenerated plants. Fluorescence in situ hybridization showed signals of telomeric sequences on the broken chromosome arm and provided evidence of de novo telomere formation. The stability of two types of altered chromosome 7 was investigated in C-banded metaphases from samples of the original callus that were collected during a period of 30–42 months after culture initiation. New alterations involving heterochromatic knobs of chromosomes 7 and 9 were observed. The aberrant chromosomes were stable in the subcultures, thus providing evidence of broken chromosome healing. The examination of anaphases showed the presence of bridges, which was consistent with the occurrence of BFB cycles. De novo telomere formation occurred in euchromatic and heterochromatic chromosome termini. The results point to events of chromosomal evolution that might occur in plants.