The genetic control of hexokinase isozymes in wheat

The genetic control of triosephosphate isomerase of hexaploid wheat and other Triticeae species

The zymogram phenotypes of triosephosphate isomerase (TPI) were determined for a large number of aneuploid derivatives of Triticum aestivum cv. ‘Chinese Spring’ and for six wheat-alien species chromosome addition series. Examination of the available compensating nullisomic-tetrasomic and homoeologous groups 3 and 5 ditelosomic lines of Chinese Spring disclosed that T. aestivum possesses two systems of dimeric TPI isozymes, designated TPI-1 and TPI-2. The genes TPI-A1, TPI-B1 and TPI-D1 were located in Chinese Spring chromosome arms 3Ap, 3Bp and 3Dp, respectively and the genes TPI-A2, TPI-B2 and TPI-D2 in chromosome arms 5Aq, 5Bq and 5Dq, respectively. TPI-1 genes were also located in Hordeum vulgare cv. Betzes chromosome 3H, T. longissimum chromosome G, Elytrigia elongata chromosome 3E, and Secale cereale cvs. Imperial and Dakold chromosome 3R. TPI-2 genes were found in Betzes chromosome 5H, T. umbellulatum chromosome 5U, T. longissimum chromosome F, and Imperial and Dakold chromosome 5R. These gene locations provide evidence of homoeology between the alien chromosomes in which the genes are located and the chromosomes of homoeologous groups 3 and 5 of Chinese Spring, respectively. Evidence was obtained for the presence of a TPI-R2 gene in each of the T. aestivum cv. Kharkov -S. cereale cv. Dakold chromosome addition lines studied suggesting that this gene is present in the wheat genome in each member of this addition series.

Chromosomal location of peptidase, PEPT-1, genes in Triticum aestivum var. Chinese Spring

Ditelocentric accessions of the Chinese Spring cultivar of Triticum aestivum were analysed electrophoretically for peptidase (PEPT) and amino peptidase (AMP = LAP) activity. Isozymic activity was missing in the accessions CSDT6AS and CSDT6BS when stained for PEPT. This was taken as evidence that the structural genes encoding these isozymes are located on the long arms of chromosomes 6A and 6B. These genes have been named Pept-A1 and Pept-B1, respectively. Isozymic activity was missing in the CSDT6BL accession when stained for AMP. This result reconfirms the previously published location of the gene Amp-B1 on the short arm of chromosome 6B and demonstrates that the two sets of loci are clearly different.

Controlled introgression to wheat of genes from rye chromosome arm 1RS by induction of allosyndesis : 2. Characterisation of recombinants

Sixteen allosyndetic recombinants involving chromosome arms 1DS and 1RS derived from the wheat-rye translocation 1DL-1RS, and one 1RS recombinant derived from 1BL-1RS were characterised by cytological, biochemical and molecular methods. Analysis of isozyme markers showed that recombination had involved different breakpoints along the 1DS arm. The gene order Tri-D1 - Per-D1 - Gpi-D1 - Gli-D1 was established on chromosome 1DS, and this is consistent with the gene order known to occur on 1BS. The use of three molecular probes for loci on 1RS confirmed one of the recombinants obtained from the 1BL-1RS translocation, and two of the three recombinants obtained from the 1DL-1RS translocation. These two recombinant chromosomes appear to have approximately reciprocal structures and may prove of direct benefit to wheat breeders as they retain the stem rust resistance of the parental translocation but have recovered some of the 1D encoded proteins which are absent in 1DL-1RS lines and which are thought to affect dough quality. A 5S RNA site was discovered on chromosome arm 1DS, probably reflecting the homoeologous relationship of this chromosome with 1BS. Segregational analysis indicated that some of the homoeologous wheat-wheat exchanges probably involved more than a single allosyndetic event.

Genetic control of the mitochondrial form of superoxide dismutase in hexaploid wheat

Extracts of mature grains of a large number of aneuploid derivatives of Triticum aestivum cv. Chinese Spring and of the members of five wheat-alien chromosome addition series were subjected to isoelectric focusing in polyacrylamide gels in order to study the genetic control of superoxide dismutase (SOD). Evidence was obtained that homologous structural genes for the mitochondrial form of SOD are located in the long arms of the homologous group 2 chromosomes of Chinese Spring and in chromosome 2R of Secale cereale cv. Imperial. The SOD gene loci located in chromosomes 2A, 2B, 2D, and 2R were designated Sod-A1, Sod-B1, Sod-D1, and Sod-R1, respectively. Chromosome-arm pairing data indicate that 2DL is not homologous to either 2AS or 2BL. The results of this study suggest, however, that 2BL is partially homologous to both 2AL and 2DL.

Duplicated chromosome segments in maize (Zea mays L.): further evidence from hexokinase isozymes

The genetic control of hexokinase isozymes (ATP: d-hexose-6-phosphotransferase, E.C. 2.7.7.1, HEX) in maize (Zea mays L.) was studied by starch gel electrophoresis. Genetic analysis of a large number of inbred lines and crosses indicates that the major isozymes observed are encoded by two nuclear loci, designated Hex1 and Hex2. Five active allozymes and one null variant are associated with Hex1, while Hex2 has nine active alleles in addition to a null variant. Alleles at both loci govern the presence of single bands, with no intragenic or intergenic heteromers visible, suggesting that maize HEX's are active as monomers. Organelle preparations demonstrate that the products of both loci are cytosolic. All alleles, including the nulls, segregate normally in crosses. Vigorous and fertile plants were synthesized that were homozygous for null alleles at both loci, suggesting that other hexosephosphorylating enzymes exist in maize that are undetected with our assay conditions. Linkage analyses and crosses with B-A translocation stocks place Hex1 on the short arm of chromosome 3, 27 centimorgans from Pgd2 (phosphogluconate dehydrogenase) and Hex2 on the long arm of chromosome 6, approximately 45 centimorgans from Pgd1. It is suggested that the parallel linkages among these two pairs of duplicated genes reflects an evolutionary history involving chromosome segment duplication or polyploidy.

Allelic variation at α-Amylase loci in hexaploid wheat

A study of α-amylase isozyme patterns from gibberellin-induced endosperms from more than 200 wheat genotypes has revealed allelic variation at five of the six α-Amy-1 and α-Amy-2 structural loci. These differences will find application as genetic markers and in varietal identification. The α-Amy-B1 locus on chromosome 6B was most variable and displayed eight distinct allelic forms. The nature of the allelic phenotypes, observations of segregating populations and the number of in vivo translation products of mRNAs from the α-Amy-1 and α-Amy-2 loci indicated that the individual loci are multigenic, each consisting of tightly linked subunits which produce several different isoforms.

The chromosomal locations of leaf peroxidase genes in hexaploid wheat, rye and barley

Eight leaf peroxidase isozymes were distinguished by IEF in 'Chinese Spring'. Two genes which control the production of three of these isozymes were located on chromosome arms 1BS and 1DS by nullisomic analysis. These loci probably form part of a homoeoallelic series and have been designated Per-B1 and Per-D1 respectively. Analysis of chromosome 1B short arm terminal deletion stocks indicated that the Per-B1 locus is located between the nucleolar organiser region and another isozyme marker, Hk-B1. Two variant leaf peroxidase phenotypes were distinguished in a small sample of hexaploid wheat varieties. Analysis of wheat-alien addition and substitution lines identified homoeologous loci in rye (Per-R1) and barley (Per-H1).