A maize Myb homolog is encoded by a multicopy gene complex

Area of Science:

• Plant genetics
• Molecular biology
• Epigenetics

Background:

• The maize P gene, a Myb-homologous regulator, controls flavonoid pigmentation in floral organs.
• Different P gene alleles exhibit distinct tissue- and organ-specific pigmentation patterns.

Purpose of the Study:

• To investigate the molecular basis for allele-specific expression patterns of the maize P gene.
• To compare two natural alleles, P-rr and P-wr, differing in expression, structure, and copy number.

Main Methods:

• Isolation and comparison of two natural maize P gene alleles (P-rr and P-wr).
• Analysis of gene structure, copy number, mRNA levels, and DNA methylation.
• Investigating the relationship between gene copy number, methylation, and tissue-specific gene expression.

Main Results:

• The P-rr allele has a single gene copy and is linked to widespread floral pigmentation.
• The P-wr allele consists of six tandemly arranged gene copies, restricting pigmentation to a subset of floral tissues.
• Despite higher copy number, P-wr exhibits reduced mRNA levels and hypermethylation compared to P-rr.
• Gene copy number and hypermethylation correlate with altered tissue-specific gene expression.

Conclusions:

• Maize P gene alleles provide a natural system to study the impact of methylation and gene copy number on gene expression.
• Somatic pairing of repeated gene copies might play a role in regulating tissue-specific gene expression patterns.