RPD3-type histone deacetylases in maize embryos.

Area of Science:

• Plant molecular biology
• Epigenetics
• Gene regulation

Background:

• Histone acetylation, regulated by histone acetyltransferases and deacetylases, is crucial for transcriptional regulation in eukaryotes.
• While RPD3-related histone deacetylases are known in nonplant systems, maize embryos exhibit three distinct deacetylase families: HD1A, HD1B, and HD2.

Purpose of the Study:

• To characterize the maize histone deacetylase HD1B family and its role in embryo development.
• To investigate the expression patterns and protein interactions of maize histone deacetylases.

Main Methods:

• Purification and cDNA cloning of maize histone deacetylases.
• Immunological studies to identify protein complexes.
• RNA blot analysis to determine mRNA expression levels.
• In vivo treatment with HC toxin to assess deacetylase inhibitor effects.

Main Results:

• Two maize histone deacetylase HD1B forms were identified as homologues of RPD3-type deacetylase HDAC1.
• HD1B, unlike HD1A and HD2, copurified with a retinoblastoma-associated protein homolog, Rbap46.
• Two HD1B mRNA species (HD1B-I and HD1B-II) were detected, with differential expression during maize embryo germination.
• HD1B-I is the major form, present throughout germination, while HD1B-II expression coincides with meristematic cell S-phase entry.
• Histone deacetylase expression was unaffected by HC toxin, but histone acetyltransferase B was downregulated.

Conclusions:

• Maize possesses a diverse set of histone deacetylases, including the RPD3-related HD1B family.
• HD1B's interaction with Rbap46 and its differential expression suggest specific roles in regulating gene expression during maize embryogenesis.
• Histone deacetylase activity is essential for normal germination, and their expression is distinct from histone acetyltransferase B regulation by HC toxin.