Gluten, major histocompatibility complex, and the small intestine: A molecular and immunobiologic approach to the spectrum of gluten sensitivity (‘celiac sprue’)

Polyploids — organisms that have multiple sets of chromosomes — are common in certain plant and animal taxa, and can be surprisingly stable. The evidence that has emerged from genome analyses also indicates that many other eukaryotic genomes have a polyploid ancestry, suggesting that both humans and most other eukaryotes have either benefited from or endured polyploidy. Studies of polyploids soon after their formation have revealed genetic and epigenetic interactions between redundant genes. These interactions can be related to the phenotypes and evolutionary fates of polyploids. Here, I consider the advantages and challenges of polyploidy, and its evolutionary potential.

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The advantages and disadvantages of being polyploid

Polyploidy is a prominent process in plants and has been significant in the evolutionary history of vertebrates and other eukaryotes. In plants, interdisciplinary approaches combining phylogenetic and molecular genetic perspectives have enhanced our awareness of the myriad genetic interactions made possible by polyploidy. Here, processes and mechanisms of gene and genome evolution in polyploids are reviewed. Genes duplicated by polyploidy may retain their original or similar function, undergo diversification in protein function or regulation, or one copy may become silenced through mutational or epigenetic means. Duplicated genes also may interact through inter-locus recombination, gene conversion, or concerted evolution. Recent experiments have illuminated important processes in polyploids that operate above the organizational level of duplicated genes. These include inter-genomic chromosomal exchanges, saltational, non-Mendelian genomic evolution in nascent polyploids, inter-genomic invasion, and cytonuclear stabilization. Notwithstanding many recent insights, much remains to be learned about many aspects of polyploid evolution, including: the role of transposable elements in structural and regulatory gene evolution; processes and significance of epigenetic silencing; underlying controls of chromosome pairing; mechanisms and functional significance of rapid genome changes; cytonuclear accommodation; and coordination of regulatory factors contributed by two, sometimes divergent progenitor genomes. Continued application of molecular genetic approaches to questions of polyploid genome evolution holds promise for producing lasting insight into processes by which novel genotypes are generated and ultimately into how polyploidy facilitates evolution and adaptation.

/pdf/genome-evolution-in-polyploids-eeag8xqgqu.pdf

Genome evolution in polyploids

Introduction.... .... . ... ..... 141 Gliadin and Glutenin 142 HMW Subunit Genes (Glu-l} 143 Genes for LMW Subunits. wand y-Gliadins (Gli-l) . ......... 146 Genes for aand f3-Gliadins (GIi-2) ........ 148 Minor Gene Loci... . 149 Allelic Variation 150 Exploitation of Variation in Plant Breeding ......... . ...... . 150

Genetics of Wheat Storage Proteins and the Effect of Allelic Variation on Bread-Making Quality

▪ Abstract Meiotic chromosomes have been studied for many years, in part because of the fundamental life processes they represent, but also because meiosis involves the formation of homolog pairs, ...

Meiotic chromosomes: integrating structure and function.

The origin of triticum spelta and its free-threshing hexaploid relatives

The discovery that the 21 different chromosomes of common wheat (Triticum aestivum L.) fall into seven homoeologous groups of three (Sears, 1952, 1954) was based primarily on the ability of each tetra-some to compensate for the nullisome of each of the other two chromosomes of the same group. Supporting evidence has come from the finding of Okamoto and Sears (1962) that the pairing in haploids is largely between chromosomes belonging to the same homoeologous group, and from the work of Riley and Kempanna (1963), who found only pairing of homoeologues when increased pairing was induced by the absence of chromosome 5B.

Nullisomic-Tetrasomic Combinations in Hexaploid Wheat

OTHER WHEAT GENES AFFECTING PAIRING . . ....... . . . . . . . . ......... . . . . ........ ...... 37 Promoters of Pairing 37 Suppressors of Pairing 38 GENES IN OTHER SPECIES THAT AFFECT PAIRING 39 THE EFFECT OF ACCESSORY CHROMOSOMES , 40

E. R. Sears

Papers

The origin of triticum spelta and its free-threshing hexaploid relatives

Nullisomic-Tetrasomic Combinations in Hexaploid Wheat

Genetic Control of Chromosome Pairing in Wheat

The Wild Gene Resources of Wheat

1B/1R wheat-rye chromosome substitutions and translocations.