title: Evolution of Gene Expression Balance Among Homeologs of Natural Polyploids.
abstract: Polyploidy is a major evolutionary process in eukaryotes, yet the expression balance of homeologs in natural polyploids is largely unknown. To study this expression balance, the expression patterns of 2180 structurally well-characterized genes of wheat were studied, of which 813 had the expected three copies and 375 had less than three. Copy numbers of the remaining 992 ranged from 4 to 14, including homeologs, orthologs, and paralogs. Of the genes with three structural copies corresponding to homeologs, 55% expressed from all three, 38% from two, and the remaining 7% expressed from only one of the three copies. Homeologs of 76-87% of the genes showed differential expression patterns in different tissues, thus have evolved different gene expression controls, possibly resulting in novel functions. Homeologs of 55% of the genes showed tissue-specific expression, with the largest percentage (14%) in the anthers and the smallest (7%) in the pistils. The highest number (1.72/3) of homeologs/gene expression was in the roots and the lowest (1.03/3) in the anthers. As the expression of homeologs changed with changes in structural copy number, about 30% of the genes showed dosage dependence. Chromosomal location also impacted expression pattern as a significantly higher proportion of genes in the proximal regions showed expression from all three copies compared to that present in the distal regions.
authors.affiliation: Department of Crop and Soil Sciences, Washington State University, Pullman, Washington 99164-6420.
authors.forename: Jasdeep S
authors.initials: JS
authors.lastname: Mutti
authors.affiliation: Department of Crop and Soil Sciences, Washington State University, Pullman, Washington 99164-6420.
authors.forename: Ramanjot K
authors.initials: RK
authors.lastname: Bhullar
authors.affiliation: Department of Crop and Soil Sciences, Washington State University, Pullman, Washington 99164-6420 ksgill@wsu.edu.
authors.forename: Kulvinder S
authors.initials: KS
authors.lastname: Gill
mesh_terms: D001483:Base Sequence; D032461:Chromosomes, Plant / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D018628:Gene Dosage; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D009928:Organ Specificity / Q000235:genetics; D020161:Physical Chromosome Mapping; D018807:Polymorphism, Single-Stranded Conformational / Q000235:genetics; D011123:Polyploidy; D012689:Sequence Homology, Nucleic Acid; D014908:Triticum / Q000235:genetics*
chemical_list: D018076:DNA, Complementary
keywords: dosage dependence; evolution of new gene functions; homoeologous gene expression; polyploidy; wheat