Isolation And Characterization Of Genes Encoding Histone Modification Enzyme And DNA Methyltransferase In Wheat (Triticum Aestivum.L)

Epigenetic regulation is a major aspect of gene control by which heritable changes in gene expression occur without an alteration in DNA sequence, which mainly includes histone code, DNA methylation, RNA interference and genomic imprinting.The study of epigentics in wheat lagged behind. In this article, genes encoding histone modification enzyme and DNA methltransferase were isolated using degenerate primer PCR and in silico cloning.The main results are as follows:1) Two histone acetyltransferase genes and four histone deacetylase genes which belonged to different types were isolated using in silico cloning and RT-PCR method, designated TaHAT1-2, TaHD1-4 respectively. Amino acid sequence analysis suggested that they all contained typical structrue characteristics of histone acetyltransferase and deacetylase. Subcellular localization indicated that TaHATl protein became concentrated in the nucleus and TaHD3 displayed nuclear-cytoplasmic distribution.To our knowledge, no genes encoding histone acetyltransferase and deacylase has been reported in wheat2) Nine SET domain protein gene fragments were obtained by degenerate-primer PCR. Phylogenetic analysis suggested that they belonged to SU (VAR) 3-9 class SET domain protein.ln addition, two SET domain protein genes were obtained using in silico cloning and RT-PCR method, named TaSET1-2 respectively. Phylogenetic analysis indicated that they belonged to ASH and SU (VAR) 3-9 class SET domain protein respectively.3) We isolated four wheat cDNA fragments and one cDNA with open reading frame encoding DNA methyltransferase and designated TaMETl, TaMET2a, TaMET2b, TaCMT and TaMET3, respectively. BLAST searches and phylogenetic analysis suggested that 5 cDNAs belonged to four classes (Dnmt1, Dnmt2, CMT and DnmG) of DNA methyltransferase genes. TaMET2a encoded a protein of 376 aa and contained eight of ten conserved motifs characteristic of DNA methyltransferase. Genomic sequence of TaMET2a was obtained and found to contain ten introns and eleven exons.4) Expression analysis of these genes obtained in this article revealed that they were expressed in developing seed, during germination and various vegetative tissues, but in quite different abundance. It was interesting to note that TaMETl and TaMET3 involved in maintenance methylation and de novo methylation were clearly detected in dry seeds and other genes had not been detected. Moreover, differential expression patterns of these genes were observed between wheat hybrid and its parents in leaf, stem and root of jointing stage, some were up-regulated while some others were down-regulated in hybrid.5) Overexpression of TaHATl and TaHD3 genes in Arabidopsis suggested that they were both associated with various developmental abnormalities, mainly including leaf and flower defect which suggested that TaHATl and TaHD3 may be involved in a general regulatory mechanism responsible for plant plasticity and variation in nature.This is a first report about function study of histone acetyltransferase and deacetylase in wheat.