Tissue culture-induced DNA methylation variation in maize

Area of Science:

• Plant molecular biology
• Epigenetics
• Maize genetics

Background:

• Plant tissue culture is a valuable tool for crop improvement.
• Tissue culture can induce somaclonal variation, including epigenetic changes.
• DNA methylation is a key epigenetic modification influencing gene expression.

Purpose of the Study:

• To investigate DNA methylation changes in maize progeny derived from tissue culture.
• To determine the frequency and stability of these epigenetic alterations.
• To explore the potential role of demethylation in tissue culture-induced variation.

Main Methods:

• Analysis of DNA methylation patterns using isoschizomers Hpa II and Msp I.
• Probing digested DNA with single-copy genomic and cDNA clones.
• Examining 21 maize progeny lines derived from tissue culture.
• Assessing inheritance of methylation changes over two generations of self-pollination.

Main Results:

• 39% of progeny families exhibited altered DNA methylation patterns, exclusively decreases (demethylation).
• Fifteen percent of methylation changes were homozygous in regenerated plants.
• Demethylation changes were stably inherited across two generations.
• No sequence variation was detected in Msp I-digested DNA.

Conclusions:

• Demethylation occurs frequently in maize tissue culture and is a significant contributor to somaclonal variation.
• The high frequency of homozygous alterations suggests a non-random mutational mechanism.
• Epigenetic instability, specifically demethylation, is a critical factor in tissue culture-induced genetic diversity in maize.