B chromosome behavior in maize pollen as determined by a molecular probe

Area of Science:

• Genetics
• Molecular Biology
• Plant Science

Background:

• B chromosomes in maize typically undergo nondisjunction during the second microspore division.
• Previous studies relied on genetic analysis and chromosome spreads, limiting detailed observation.
• The preferential fertilization by B chromosome-carrying sperm influences inheritance patterns.

Purpose of the Study:

• To develop and apply fluorescence in situ hybridization (FISH) for detecting B chromosomes in intact maize pollen.
• To quantify the frequency of B chromosome nondisjunction using a B chromosome-specific probe.
• To investigate the timing and location of B chromosome behavior during microsporogenesis.

Main Methods:

• Utilized a B chromosome-specific probe for fluorescence in situ hybridization (FISH).
• Analyzed intact interphase nuclei within mature maize pollen.
• Employed genetic line TB-10L18 for consistent B chromosome analysis.

Main Results:

• FISH successfully detected B chromosomes in intact pollen nuclei, revealing their presence, location, and frequency.
• Nondisjunction of the B centromere occurred at an average frequency of 56.6% in the analyzed maize line.
• Evidence suggests B chromosome nondisjunction may also occur during the first microspore division.
• Observed specific spatial distribution of B chromosomes within sperm nuclei and hybridization to external DNA fragments.

Conclusions:

• FISH provides a robust method for studying B chromosome behavior in maize pollen.
• The high frequency of B chromosome nondisjunction is confirmed and quantified.
• B chromosome nondisjunction dynamics are more complex than previously understood, potentially involving earlier meiotic stages.