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

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.

Single-copy gene fluorescence in situ hybridization and genome analysis: Acc-2 loci mark evolutionary chromosomal rearrangements in wheat

“…This procedure does not need detection and blocking steps, which were previously being used in indirect FISH to visualize gene clusters and repeats (Mukai et al 1993;Pedersen and Langridge 1997;Turner et al 1999;Li et al 2003;Turnbull et al 2003;Szakacs and Molnar-Lang 2007;Cuadrado et al 2008a, b) or a signal-amplification step in tyramide-FISH (Perez et al 2009). …”

“…In wheat, gene-specific probes and probes for tandem repeats, including oligonucleotide probes, were used in indirect FISH with blocking to detect tandem repeats and gene clusters (Mukai et al 1993;Pedersen and Langridge 1997;Turner et al 1999;Li et al 2003;Turnbull et al 2003;Szakacs and Molnar-Lang 2007;Cuadrado et al 2008 a, b). Indirect FISH uses nonfluorescent chemicals for labeling and needs an additional detection step for visualizing the hybridization site and amplifying of the signal.…”

Sequencing of the Triticum monococcum Hardness locus reveals good microcolinearity with rice

“…The puroindoline proteins are more similar to each other (71%) than to the Grain Softness Related Protein (Gsp, 57-58%). These three related genes are physically close to each other in both the A m and D genomes (Tranquilli et al 1999;Turnbull et al 2003), suggesting that they originated by two independent duplication events (Tranquilli et al 1999). Studies of natural mutations (Morris 2002) and deletions (Tranquilli et al 2002), and work on transgenic wheat (Beecher et al 2002), have confirmed that the puroindoline genes are the ones responsible for the differences in grain texture.…”

Bioactive Beads-Mediated Transformation of Rice with Large DNA Fragments Containing Aegilops tauschii Genes, with Special Reference to Bead-Production Methodology

“…The hardness genes consist of three genes (puroindoline a, puroindoline b, GSP-1 gene) and are scattered in a ca. 100 kb region on the short arm of chromosome 5D in Aegilops tauschi (Turnbull et al, 2003). The BAC DNA encompasses the hardness locus and also contains the regulatory regions of each gene (Fig.…”