Recruitment of closely linked genes for divergent functions: the seed storage protein (Glu-3) and powdery mildew (Pm3) genes in wheat (Triticum aestivum L.).
Wheat seed storage protein gene loci (Glu-3) and powdery mildew resistance gene loci (Pm3 and Pm3-like) are closely linked on the short arms of homoeologous group 1 chromosomes. To study the structural organization of the Glu-3/Pm3 loci, three bacterial artificial chromosome clones were sequenced from the A, B, and D genomes of hexaploid wheat. The A and B genome clones contained a Glu-3 adjacent to a Pm3-like gene organized in a conserved Glu-3/SFR159/Pm3-like structure. The D genome clone contained clusters of resistance gene analogs but no Pm3. Its similarity to the A and B genome was limited to the Glu-3/SFR159 region. Comparison of the B genome PM3-like deduced amino acid sequence with known PM3 functional isotypes reinforced the hypothesis of allelic evolution via block exchange by gene conversion/recombination. The advent of glutenin genes and the formation of the Glu-3/SFR159/Pm3 locus occurred after divergence of wheat from rice and Brachypodium. Comparison of the A genome homologous sequences permitted an estimate of time of divergence of approximately 0.3 million years ago. The B genome sequences were not colinear indicating that they could either be paralogs or represent different B genome progenitors. Analysis of the 11 complete retrotransposons indicated a time of divergence ranging from 0.29 to 5.62 million years ago, consistent with their complex nested structure.
Wang
Zi-Ning
ZN
Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, MB, Canada, R3T 2M9.
Huang
Xiu-Qiang
XQ
Cloutier
Sylvie
S
D000595:Amino Acid Sequence; D001203:Ascomycota / Q000502:physiology*; D019143:Evolution, Molecular; D017343:Genes, Plant / Q000235:genetics*; D008040:Genetic Linkage; D056426:Genetic Loci / Q000235:genetics; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018626:Retroelements / Q000235:genetics; D055314:Seed Storage Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014908:Triticum / Q000235:genetics* / Q000382:microbiology
D010940:Plant Proteins; D018626:Retroelements; D055314:Seed Storage Proteins