Differences in DNA-methylation are associated with a paramutation phenomenon in transgenic petunia

Area of Science:

• Plant Molecular Biology
• Epigenetics
• Genetics

Background:

• Transgenic petunias expressing the maize A1 gene exhibit brick-red pigmentation.
• A white derivative (17-W) was identified, showing hypermethylation of the A1 gene's promoter, unlike the hypomethylated state in the pigmented line (17-R).

Purpose of the Study:

• To investigate the mechanism behind the altered pigmentation in the 17-W petunia line.
• To explore the potential paramutation-like interactions between differentially methylated A1 alleles.

Main Methods:

• Analysis of A1 gene expression and methylation patterns in transgenic petunia lines (17-R and 17-W).
• Observation of progeny phenotypes resulting from crosses between lines carrying different A1 alleles.
• Comparison with known paramutation phenomena in plants.

Main Results:

• Plants carrying both 17-R and 17-W alleles displayed reduced and variable pelargonidin pigmentation, indicating a semidominant inhibitory effect of the 17-W allele.
• Differential methylation patterns between alleles were observed, suggesting a role in the observed paramutation-like effect.
• The findings suggest homology-dependent interlocus trans-inactivation mechanisms.

Conclusions:

• The study reveals a paramutation-like phenomenon in petunias mediated by differential DNA methylation and somatic homologous pairing.
• This interaction between alleles leads to heritable changes in gene function, impacting flower color.
• The findings support a common mechanism for homology-dependent trans-inactivation across different plant systems.