Genetic and epigenetic alteration among three homoeologous genes of a class E MADS box gene in hexaploid wheat.
Bread wheat (Triticum aestivum) is a hexaploid species with A, B, and D ancestral genomes. Most bread wheat genes are present in the genome as triplicated homoeologous genes (homoeologs) derived from the ancestral species. Here, we report that both genetic and epigenetic alterations have occurred in the homoeologs of a wheat class E MADS box gene. Two class E genes are identified in wheat, wheat SEPALLATA (WSEP) and wheat LEAFY HULL STERILE1 (WLHS1), which are homologs of Os MADS45 and Os MADS1 in rice (Oryza sativa), respectively. The three wheat homoeologs of WSEP showed similar genomic structures and expression profiles. By contrast, the three homoeologs of WLHS1 showed genetic and epigenetic alterations. The A genome WLHS1 homoeolog (WLHS1-A) had a structural alteration that contained a large novel sequence in place of the K domain sequence. A yeast two-hybrid analysis and a transgenic experiment indicated that the WLHS1-A protein had no apparent function. The B and D genome homoeologs, WLHS1-B and WLHS1-D, respectively, had an intact MADS box gene structure, but WLHS1-B was predominantly silenced by cytosine methylation. Consequently, of the three WLHS1 homoeologs, only WLHS1-D functions in hexaploid wheat. This is a situation where three homoeologs are differentially regulated by genetic and epigenetic mechanisms.
Shitsukawa
Naoki
N
Department of Bioscience, Fukui Prefectural University, Fukui, Japan.
Tahira
Chikako
C
Kassai
Ken-Ichiro
K
Hirabayashi
Chizuru
C
Shimizu
Tomoaki
T
Takumi
Shigeo
S
Mochida
Keiichi
K
Kawaura
Kanako
K
Ogihara
Yasunari
Y
Murai
Koji
K
D017360:Arabidopsis / Q000235:genetics; D001483:Base Sequence; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D035264:Flowers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D006824:Hybridization, Genetic; D026161:MADS Domain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011123:Polyploidy; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012689:Sequence Homology, Nucleic Acid; D014908:Triticum / Q000235:genetics*
D026161:MADS Domain Proteins; D010940:Plant Proteins