Characterization of a maize isochromosome 8S*8S

Area of Science:

• Plant genetics
• Cytogenetics
• Molecular biology

Background:

• Isochromosomes are structural chromosomal abnormalities.
• Characterizing such aberrations is crucial for understanding genome stability and inheritance.

Purpose of the Study:

• To identify and characterize an isochromosome in maize using cytogenetic methods.
• To investigate the meiotic behavior, transmission, and genetic consequences of this isochromosome.

Main Methods:

• Somatic karyotyping utilizing multiprobe fluorescence in situ hybridization (FISH).
• Cytological analysis of meiotic stages (pachytene, anaphase, telophase).
• FISH confirmation of chromosome origin and centromere repeat analysis.

Main Results:

• An isochromosome of maize chromosome 8 short arm origin was detected in the HiII Parent B line.
• The isochromosome exhibited abnormal meiotic pairing, lagging, and transmission rates of 17%-20%.
• Significant copy number variation in CentC centromere repeats occurred within one generation, impacting plant phenotype and fertility.

Conclusions:

• The somatic karyotyping system effectively identified and characterized this chromosomal aberration.
• The study highlights rapid centromere evolution and its phenotypic effects in maize.
• Isochromosome presence negatively affects plant growth, development, and reproductive success.