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The organization of genes tightly linked to the Ha locus in Aegilops tauschii, the D-genome donor to wheat

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Abstract:

The grain hardness locus, Ha, is located at the distal end of the short arm of chromosome 5D in wheat. Three polypeptides, puroindoline-a, puroindoline-b, and grain softness protein (GSP-1), have been identified as components of friabilin, a biochemical marker for grain softness, and the genes for these polypeptides are known to be tightly linked to the Ha locus. However, this region of the chromosome 5D has not been well characterized and the physical distance between the markers is not known. Separate lambda clones containing the puroindoline-a gene and the puroindoline-b gene have been isolated from an Aegilops tauschii (the donor of the D genome to wheat) genomic lambda library and investigated. Considerable variation appears to exist in the organization of the region upstream of the gene for puroindoline-b among species closely related to wheat. Using in situ hybridization the genes for puroindoline-a, -b, and GSP-1 were demonstrated to be physically located at the tip of the short arm of chromosome 5 of A. tauschii. Four overlapping clones were isolated from a large-insert BAC library constructed from A. tauschii and of these one contained genes for all of puroindoline-a, puroindoline-b, and GSP-1. The gene for puroindoline-a is located between the other two genes at a distance no greater than approximately 30 kb from either gene. The BAC clone containing all three known genes was used to screen a cDNA library constructed from hexaploid wheat and cDNAs that could encode novel polypeptides were isolated.Key words: puroindolines, GSP-1, chromosome 5D, BAC library, tauschii.

Le locus déterminant la dureté des grains, Ha, est situé à l'extrémité distale du bras court du chromosome 5D chez le blé. Trois polypeptides, la puroindoline-a, la puroindoline-b et la GSP-1, ont été identifiés comme faisant partie de la friabiline, un marqueur biochimique pour la tendreté des grains et les gènes codant pour ces polypeptides sont fortement liés au locus Ha. Cependant, cette région du chromosome 5D n'est pas très bien caractérisée et les distances physiques entre ces marqueurs est inconnue. Des clones génomiques distincts (dans des phages lambda) contenant le gène de la puroindoline-a ou celui de la puroindoline-b ont été isolés d'une banque génomique de l'Aegilops tauschii (l'espèce ayant contribué le génome D du blé) et caractérisés. Il semblerait y avoir une variation considérable quant à l'organisation de la région 5' du gène de la puroindoline-b au sein des espèces très apparentées au blé. Par hybridation in situ, en utilisant les gènes codant pour la puroindoline-a, -b ou la GSP-1 comme sondes, il a été montré que ces gènes sont localisés à l'extrémité de bras court du chromosome 5 de l'A. tauschii. Quatre clones se chevauchant ont été isolés à partir d'une banque de clones BAC préparée avec l'ADN de l'A. tauschii et l'un de ceux-ci contenait les gènes codant pour la puroindoline-a, la puroindoline-b et la GSP-1. Le gène codant pour la puroindoline-a es t situé entre les deux autres à moins de 30 kb de l'un et l'autre. Le clone BAC contenant les trois gènes connus a été employé pour cribler une banque d'ADNc produite chez le blé hexaploïde et des ADNc pouvant coder pour des polypeptides nouveaux ont été isolés.Mots clés : puroindolines, GSP-1, chromosome 5D, banque de clones BAC, tauschii.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: April 1, 2003

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  • From its inception in 1957, this international cytogenetics journal has catered to the research areas of the members of the Genetics Society of Canada; traditionally, these have included agriculture, entomology, genetics/cytogenetics, and evolutionary mechanisms. The contents of the journal have evolved as contributors developed new technologies and interests. A 20-member Editorial Board is composed of scientists from around the world. Reviews and commentary from respected experts are often featured.
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