A candidate recombination modifier gene for Zea mays L

Area of Science:

• Plant genetics
• Molecular biology
• Cytogenetics

Background:

• Meiosis is crucial for sexual reproduction in plants, involving precise chromosome pairing and segregation.
• Recombination, the exchange of genetic material between homologous chromosomes, is a key event during meiotic prophase I.
• The maize desynaptic (dy) mutant affects meiotic processes, suggesting a potential role in regulating recombination.

Purpose of the Study:

• To investigate whether the maize meiotic mutant desynaptic (dy) functions as a recombination modifier gene.
• To compare recombination rates in desynaptic (dy) mutants versus wild-type maize using genetic and cytogenetic approaches.

Main Methods:

• Segregation analysis of six linked molecular markers on chromosome 1L in F2 desynaptic (dy/dy) and wild-type plants.
• Cytogenetic analysis using fluorescence in situ hybridization (FISH) to visualize meiotic configurations at metaphase I.
• Estimation of chromosome map lengths and chiasma frequencies using the expectation-maximization algorithm.

Main Results:

• Chromosome 1L map length was significantly reduced in desynaptic (dy/dy) plants (45-63 cM) compared to wild type (72 cM).
• Chiasma frequencies were significantly decreased in desynaptic (dy/dy) plants for chromosome 2 arms, chromosome arm 6L, and eight other chromosomes.
• An increase in chiasma frequency was observed in desynaptic (dy/dy) plants specifically for chromosome arm 6S, which harbors the nucleolus-organizing region.

Conclusions:

• The maize desynaptic (dy) mutant is confirmed to be a recombination modifier gene.
• The desynaptic mutation impacts recombination rates differentially across the maize genome, with a notable exception at the 6S chromosome arm.
• These findings provide insights into the genetic control of recombination during plant meiosis.