C. N. Chinoy

Chromosomal rearrangements in the rye genome relative to that of wheat

SummaryAn RFLP-based genetic map of Secale Cereale has provided evidence for multiple evolutionary translocations in the rye genome relative to that of hexaploid wheat. DNA clones which have previously been mapped in wheat indicated that chromosome arms 2RS, 3RL, 4RL, 5RL, 6RS, 6RL, 7RS and 7RL have all been involved in at least one translocation. A possible evolutionary pathway, which accounts for the present day R genome relative to the A, B and D genomes of wheat, is presented. The relevance of these results for strategies designed to transfer useful genes from rye, and probably other related species, to wheat is discussed.

RFLP-based genetic map of the homoeologous group 3 chromosomes of wheat and rye

SummaryGenetic maps of chromosomes 3A, 3B and 3D of wheat and 3R of rye were developed using 22 DNA probes and two isozyme marker systems. Analysis of the 49 loci mapped showed extreme clustering around the centromere in all four maps, with large ‘gaps’ in the distal chromosome regions, which is interpreted as being due to strong localisation of recombination towards the ends of the wheat and rye chromosomes. In the centromeric regions gene orders are highly conserved between the three wheat genomes and the rye genome. However, the unpredictable behaviour of the DNA clones that map in distal chromosome locations may indicate that the genomes are diverging most rapidly in the regions of higher recombination. A comparison of cDNA and genomic probes showed the latter to be much more efficient for revealing RFLP. Some classes of gDNA clones, i.e. chromosome-specific sequences and those hybridizing in a non-homoeologous manner, were seen to be most polymorphic. Correlations between map locations and RFLP levels showed no clear relationship. In addition to anonymous DNA clones, the locations of known function clones, sedoheptulose-1,7-bisphosphatase (XSbp), carboxypeptidase I (XCxp1) and a bZIP protein (XEmbp), were ascertained along with those for two isozyme loci, Mal-1 and Est-5.

Nonhomoeologous translocations between group 4, 5 and 7 chromosomes within wheat and rye.

SummaryGenetic maps of wheat chromosome 4A and rye chromosome arm 5RL, and the chromosomal locations of 70 sets of isozyme and molecular homoeoloci have been used to further define the structure of wheat chromosomes 4A, 5A and 7B, and rye chromosomes 4R, 5R and 7R. We provide evidence, for the first time, which is consistent with the presence of an interstitial segment on 4AL originating from 5AL, and of a segment originally from 5RL on 7RS. The evolutionary origins of the present chromosomes are discussed.

Comparative RFLP-based genetic maps of barley chromosome 5 (1H) and rye chromosome 1R.

SummaryA genetic map of barley chromosome 5 (1H) was constructed using DNA markers. Seventeen loci were mapped to 15 locations, and these included the known-function loci (in order from the most distal on the long arm) XAdh (alcohol dehydrogenase), XLec (homologous to wheat germ agglutinin), XHor3 (D-hordein), XPpdk (pyruvate orthophosphate dikinase), centromere, XIcal (chymotrypsin inhibitor), and 6 loci in the B- and C-hordein cluster towards the end of the short arm. The gene order on the barley map agreed closely with that of chromosome 1 of rye. Intervarietal comparisons showed that single-copy cDNA and genomic DNA probes revealed about twice the level of RFLPs found in wheat.

RFLP-based genetic map of rye (Secale cereale L.) chromosome 1R

SummaryA map of chromosome 1R of rye was constructed using 16 molecular and biochemical loci. From long arm to short arm, known-function loci were placed in the order: XAdh — XLee — Glu-R1[Sec-3] — XPpdk-1R — XEm-1R-1 — XEm-1R-2 — Centromere — XNor-R1 —Gpi-R1 — XGli-R1 [Sec-1a] along with six anonymous genomic and cDNA clones from wheat. The map, which spans 106 cM with 12 loci clustered in a 15-cM region around the centromere, shows reasonably good agreement with previously published maps for the centromeric region, whereas the XNor-R1 — Gpi-R1 region gives a much larger distance than previously reported.

Chromosomal location of the genes for ferredoxin in wheat, barley and rye.

cDNA derived from poly(A +) RNA extracted from young wheat leaves (Triticum aestivum) was used in the construction of a 2 gt 11 expression library (Raines et al. 1988). The library was screened using a polyclonal antibody that had been raised against the ferredoxin of pea (Pisum sativum). An insert of 0.5 kbp from a plaque that reacted positively with the antibody was subcloned and used as a probe, to isolate a gene from a wheat genomic library in 2 Charon 35 (Lloyd et al. 1991), and its complete coding sequence was determined (D. Bringloe, unpublished results). A 1.3-kbp HindIII genomic fragment was used as a probe for gene localization.

The coding sequence for sedoheptulose-1,7-bisphosphatase detects multiple homologues in wheat genomic DNA

The clone

Chromosomal location in wheat of the genes coding for the acyl carrier proteins I and III

9.2 was isolated from a wheat eDNA expression library in 2gtlt (Raines eta1. 1988; Chinoy etal. 1991) by screening with polyelonal antibodies which had been raised to maize sedoheptulose-l,7-bisphosphatase (SBPase) (Nishizawa and Buchanan 1981). The insert from a plaque which gave a positive reaction with the antibodies was subcloned into a plasmid for further analysis. A detailed description of the characterization of

Chromosomal location and RFLP utility in wheat and barley of a wheat gene with homology to a 7S storage-globulin sequence.

9.2 and of cDNA and genomic clones encompassing the entire coding sequence of SBPase is given by Raines et al. (1992).

RFLP mapping of rye chromosome 7R reveals a highly translocated chromosome relative to wheat

Source of the probes A cDNA library in 2gt 11 was constructed from poly(A +) RNA, isolated from barley seedling leaves. The library was screened with a 66-bp oligonucleotide probe, constructed on the basis of the cDNA sequence of ACP I of spinach and the highly conserved region of ACP I of barley. Inserts from 22 positive plaques were isolated and subcloned into the EcoRI site of pUC18. Sequencing demonstrated that 19 out of the 22 clones coded for the chloroplastic acyl carrier protein I (ACP I). The 3 other clones coded for the acyl carrier protein III (ACP III), which is thought to be achloroplastic. No clones were obtained for the chloroptastic acyl carrier protein II (ACP II). Two clones were selected as probes for the gene localization: pACPll , with an insert of 768 bp coding for ACP I, and pACP1, with an insert of 520 bp coding for ACP III (Hansen 1987; yon WettsteinKnowles 1989).