Morimoto R, Kosugi T, Nakamura C, Takumi S.
Intragenic diversity and functional conservation of the three homoeologous loci of the KN1-type homeobox gene Wknox1 in common wheat.
Plant Mol. Biol.
Common wheat represents a typical allohexaploid species and provides a good experimental system for studying genomic alterations associated with allopolyploidization. We studied three homoeologous loci of wheat Wknox1 gene, which is highly homologous to the knotted1 (kn1)-like homeobox (KNOX) genes functioning at shoot apical meristems (SAM). Wknox1 transcripts were detected in SAM, and its overexpression caused abnormal leaf morphology with occasional ectopic leaves in transgenic tobacco plants. A comparative study of the three Wknox1 genomic sequences revealed accumulation of a large number of mutations including insertions and deletions, particularly in the fourth intron and the 5'-upstream region. Some structural mutations including MITE-insertions were allocated in the evolutionary lineage of the wheat genome, suggesting that they occurred at all stages of wheat evolution. A mutation rate was the highest in the Wknox1b locus, which is consistent with the known highest degree of differentiation in the B genome. Despite the structural differentiation, all three Wknox1 homoeologs showed an identical expression pattern in wheat and their promoter regions induced the conserved expression pattern in transgenic tobacco plants. A potential of the intragenic diversity in homoeologs of essential genes as a tool for studying the genome evolution associated with allopolyploidization was discussed.
5' Flanking Region / genetics
DNA Transposable Elements / genetics
DNA, Plant / chemistry
DNA, Plant / genetics*
Exons / genetics
Gene Expression Profiling
Genes, Plant / genetics
Glucuronidase / genetics
Glucuronidase / metabolism
Homeodomain Proteins / genetics*
Homeodomain Proteins / physiology
Introns / genetics
Molecular Sequence Data
Plant Proteins / genetics*
Plant Proteins / physiology
Plants, Genetically Modified
Polymorphism, Single Nucleotide
Protein Isoforms / genetics
Recombinant Fusion Proteins / genetics
Recombinant Fusion Proteins / metabolism
Sequence Analysis, DNA
Sequence Homology, Nucleic Acid
Triticum / genetics*
Triticum / physiology
BIOCHEMISTRY & MOLECULAR BIOLOGY