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The modification of crossing over in maize by extraneous chromosomal elements
1Department of Botany, Indiana University, Bloomington, Indiana, USA.
Summary
Maize recombination rates are influenced by B chromosomes and abnormal chromosome 10. B chromosomes increase crossing over on chromosome 5, with a dosage effect, while abnormal chromosome 10 enhances it more in females.
Area of Science:
- Genetics
- Molecular Biology
- Plant Science
Background:
- Recombination frequency is a critical factor in genetic inheritance and evolution.
- Endogenous factors, such as chromosomal abnormalities and sex, can significantly influence recombination rates in maize.
- Understanding these influences is key to maize breeding and genetic studies.
Purpose of the Study:
- To investigate the impact of B chromosomes and abnormal chromosome 10 on recombination frequencies in specific maize genome regions.
- To determine if there is a dosage effect of B chromosomes on recombination.
- To compare the effects of B chromosomes and abnormal chromosome 10 across different chromosomal segments and sexes.
Main Methods:
- Analysis of recombination frequencies in five distinct maize genome regions.
- Utilizing maize plants with varying numbers of B chromosomes (0, 1, 2, 4).
- Comparing recombination rates in plants heterozygous for abnormal chromosome 10 (K10 k10) versus homozygous for standard chromosome 10 (k10 k10).
Main Results:
- B chromosomes increased recombination in proximal chromosome 5 segments, with a dosage effect and greater impact in male meiocytes.
- Abnormal chromosome 10 significantly enhanced crossing over in chromosome 5 segments, with a stronger effect in female sporocytes.
- Recombination in chromosome 9 segments showed varied responses to B chromosomes and abnormal chromosome 10, suggesting differential heterochromatin properties.
Conclusions:
- B chromosomes and abnormal chromosome 10 are significant endogenous factors modulating maize recombination.
- The effects of these chromosomal abnormalities are region-specific and sex-dependent.
- Proximal heterochromatin on chromosome 9 exhibits distinct properties compared to other maize chromosomes regarding recombination modulation.
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