In Vivo DNA Affinity Purification and Histone Deacetylase Inhibitor Treatment Proves the Role of Histone Acetylation in the Expression Regulation of High-Molecular-Weight Glutenin Genes

Abstract

High-molecular-weight glutenin subunit (HMW GS) proteins are major components of the gluten matrix, which is the physical basis of bread-making in wheat. Epigenetic and transcriptional regulations of HMW GS genes were studied both in silico and in wet lab to understand their tissue (endosperm) specific expression. Our co-expressional network analysis identified key transcription factor (TF) genes that regulate HMW GS genes. We also show here that HMW GS genes are inhibited in vegetative tissues by histone deacetylation as revealed by strong GUS expression in vascular tissues of transgenic barley seedlings harbouring HMW GS gene promoter::uidA-reporter gene fusions upon treatment with a histone deacetylase inhibitor. A novel method termed in vivo DNA affinity purification (IP) has been developed here for the isolation of histones and transcription factors binding to target DNA regions. The technique is based on the biolistic introduction of biotinylated PCR probes amplified from HMW GS gene promoters into wheat leaves. Twenty-four hours later, the probe is cross-linked with interacting factors and subsequently re-purified from plant nuclear extracts. Many proteins, ribosomal proteins and histones have so far been isolated. No lysine-acetylated histone protein fragments were found which further highlight the inhibiting effect of histone deacetylation on HMW GS gene expression.