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G E Hart

Publications and source records attributed to G E Hart.

At least 19 recordsLinked to original sources
PubMed2006

Alignment of genetic maps and QTLs between inter- and intra-specific sorghum populations.

To increase the value of associated molecular tools and also to begin to explore the degree to which interspecific and intraspecific genetic variation in Sorghum is attributable to corresponding genetic loci, we have aligned genetic maps derived from two sorghum populations that share one common parent (Sorghum bicolor L. Moench accession BTx623) but differ in morphological and evolutionarily distant alternate parents (S. propinquum or S. bicolor accession IS3620C). A total of 106 well-distributed DNA markers provide for map alignment, revealing only six nominal differences in marker order that are readily explained by sampling variation or mapping of paralogous loci. We also report a total of 61 new QTLs detected from 17 traits in these crosses. Among eight corresponding traits (some new, some previously published) that could be directly compared between the two maps, QTLs for two (tiller height and tiller number) were found to correspond in a non-random manner (P<0.05). For several other traits, correspondence of subsets of QTLs narrowly missed statistical significance. In particular, several QTLs for leaf senescence were near loci previously mapped for 'stay-green' that have been implicated by others in drought tolerance. These data provide strong validation for the value of molecular tools developed in the interspecific cross for utilization in cultivated sorghum, and begin to separate QTLs that distinguish among Sorghum species from those that are informative within the cultigen (S. bicolor).

Chromosome Mapping↗
PubMed2000

An integrated SSR and RFLP linkage map of Sorghum bicolor (L.) Moench.

We report the development, testing, and use (for genetic mapping) of a large number of polymerase chain reaction (PCR) primer sets that amplify DNA simple sequence repeat (SSR) loci of Sorghum bicolor (L.) Moench. Most of the primer sets were developed from clones isolated from two sorghum bacterial artificial chromosome (BAC) libraries and three enriched sorghum genomic-DNA (gDNA) libraries. A few were developed from sorghum DNA sequences present in public databases. The libraries were probed with radiolabeled di- and trinucleotide oligomers, the BAC libraries with four and six oligomers, respectively, and the enriched gDNA libraries with four and three oligomers, respectively. Both types of libraries were markedly enriched for SSRs relative to a size-fractionated gDNA library studied earlier. However, only 2% of the sequenced clones obtained from the size-fractionated gDNA library lacked a SSR, whereas 13% and 17% of the sequenced clones obtained from the BAC and enriched gDNA libraries, respectively, lacked a SSR. Primer sets were produced for 313 SSR loci. Two-hundred sixty-six (85%) of the loci were amplified and 165 (53%) of the loci were found to be polymorphic in a population composed of 18 diverse sorghum lines. (AG/TC)n and (AC/TG)n repeats comprised 91% of the dinucleotide SSRs and 52% of all of the SSRs at the polymorphic loci, whereas four types of repeats comprised 66% of the trinucleotide SSRs at the loci. Primer sequences are reported for the 165 polymorphic loci and for eight monomorphic loci that have a high degree of homology to genes. Also reported are the genetic map locations of 113 novel SSR loci (including four SSR-containing gene loci) and a linkage map composed of 147 SSR loci and 323 RFLP (restriction fragment length polymorphism) loci. The number of SSR loci per linkage group ranges from 8 to 30. The SSR loci are distributed relatively evenly throughout approximately 75% of the 1406-cM linkage map, but segments of five linkage groups comprising about 25% of the map either lack or contain few SSR loci. Mapping of SSR loci isolated from BAC clones located to these segments is likely to be the most efficient method for placing SSR loci in the segments.

Alleles↗
PubMed1998

Physical mapping of the liguleless linkage group in Sorghum bicolor using rice RFLP-selected sorghum BACs.

Physical mapping of BACs by fluorescent in situ hybridization (FISH) was used to analyze the liguleless (lg-1) linkage group in sorghum and compare it to the conserved region in rice and maize. Six liguleless-associated rice restriction fragment length polymorphism (RFLP) markers were used to select 16 homeologous sorghum BACs, which were in turn used to physically map the liguleless linkage group in sorghum. Results show a basic conservation of the liguleless region in sorghum relative to the linkage map of rice. One marker which is distal in rice is more medial in sorghum, and another marker which is found within the linkage group in rice is on a different chromosome in sorghum. BACs associated with linkage group I hybridize to chromosome It, which was identified by using FISH in a sorghum cytogenetic stock trisomic for chromosome I (denoted It), and a BAC associated with linkage group E hybridized to an unidentified chromosome. Selected BACs, representing RFLP loci, were end-cloned for RFLP mapping, and the relative linkage order of these clones was in full agreement with the physical data. Similarities in locus order and the association of RFLP-selected BAC markers with two different chromosomes were found to exist between the linkage map of the liguleless region in maize and the physical map of the liguleless region in sorghum.

Basic-Leucine Zipper Transcription Factors↗
PubMed1995

Characterization and expression of rpoC2 in CMS and fertile lines of sorghum.

A 165 bp deletion in the middle of rpoC2, the plastid gene which encodes the RNA polymerase beta" subunit, was identified in the small-anthered types of CMS sorghum, Sorghum bicolor (L.). Moench, containing A1, A2, A5, and A6 cytoplasms. It was previously shown that the amino acid sequence deleted in these CMS lines is in a monocot-specific region that contains several protein motifs that are characteristic of several transcription factors. Using primers flanking the deletion in PCR analyses, various types of CMS lines, some of which are used in hybrid sorghum production, were classified into two groups. CMS lines containing A1, A2, A5, A6 cytoplasms display the deletion in rpoC2. These lines have small anthers in which pollen development is arrested at an early stage and in which usually only empty exines are found. CMS lines containing A3, A4, and 9E cytoplasms do not possess the deletion. These lines have large anthers in which pollen degenerates at a later stage. Run-on transcription assays using 15 chloroplast genes showed that chloroplast gene transcription rates are similar in CMS and fertile (maintainer and restorer) lines and F1 in seedling leaves. Analyses of RNA blots indicated that rbcL, rpoB and rpoC2 transcripts are accumulated mainly in the leaves and low in the inflorescence tissues and pollen. These data document plastid gene expression in leaves and non-photosynthetic tissues from CMS and fertile lines of sorghum.

Base Sequence↗
PubMed1993

A chloroplast DNA deletion located in RNA polymerase gene rpoC2 in CMS lines of sorghum.

Fertile lines of sorghum (Sorghum bicolor) were shown to differ from cytoplasmic male sterile (CMS) lines by the presence of a 3.8 kb HindIII chloroplast DNA fragment in the former and a smaller (3.7 kb) fragment in the latter. DNA/DNA hybridization studies showed that these two fragments are homologous. Fertile plants from S. versicolor, S. almum, S. halepense, and Sorghastrum nutans (Yellow Indiangrass) also have the 3.8 kb fragment, and CMS lines studied containing A1, A2 and A3 cytoplasms have the 3.7 kb fragment. The size difference between the two fragments was localized to a 1.0 kb SacI-HindIII fragment by restriction mapping. A 165 bp deletion, which is flanked by a 51 bp tandem repeat, was identified in the CMS lines by sequencing the clones. Comparison of the two sequences with those from maize, rice, tobacco, spinach, pea, and liverwort revealed that the deleted sequence is located in the middle of the RNA polymerase beta" subunit encoded by the gene rpoC2. The amino acid sequence deleted in the CMS lines is in a monocot-specific region which contains two protein motifs that are characteristic of several transcriptional activation factors, namely, a leucine zipper motif and an acidic domain capable of forming an amphipathic alpha-helix. Further studies designed to determine whether or not the deletion is involved in CMS of sorghum are underway.

Amino Acid Sequence↗
PubMed1993

Primers that amplify inserts in a multicloning site also hybridize to Sorghum bicolor DNA.

One or both members of a pair of primers developed to permit polymerase chain reaction amplification of sorghum DNA fragments cloned into the PstI site of pUC18 were shown to hybridize to sorghum DNA. The presence of the same primer sequences on the ends of amplified inserts posed a problem in using the amplified inserts as hybridization probes because the high signal level of the primer-detected DNA fragments often obscured the segregation patterns of the restriction fragments detected by the insert DNA. Conditions that favor annealing of the insert rather than the primers were experimentally defined, however, so that directly amplified DNA sequences could be used as RFLP probes. Cosegregation analysis of 51 F2 individuals from a cross between BTx 623 and IS 3620C established a linkage group containing the Pd1 locus. Alleles at the locus are revealed as codominant bands on Southern blots of heterozygotes, but the segregation ratio among the F2 progeny deviated significantly from the expected 1:2:1. The distortion favored the allele from parent BTx 623.

Base Sequence↗
PubMed1988

Genetic analysis of Triticeae shikimate dehydrogenase.

Starch gel electrophoresis and polyacrylamide gel isoelectric focusing (IEF) were used to investigate the genetic control of Triticeae shikimate dehydrogenase-1 (SKDH-1). Studies of wheat-alien species chromosome addition lines established that Skdh-1 of Hordeum vulgare cv. Betzes is located in chromosome 5H, Skdh-V1 of Dasypyrum villosum in 5V, Skdh-R1 of Secale cereale cvs. Dakold and King II in 5R, and Skdh-S1(1) of Triticum longissimum in 5S1S. Also, the chromosomal locations of the genes that encode SKDH-1 in T. aestivum cv. Chinese Spring, T. umbellulatum, and S. cereale cv. Imperial, determined earlier using zone electrophoresis, were reconfirmed using IEF. Zone electrophoresis and IEF do not differ markedly in their ability to detect the expression of alien Skdh-1 genes in wheat-alien species chromosome addition lines. However, IEF may be superior to zone electrophoresis as a technique for detecting and analyzing SKDH-1 genetic variants within Triticeae species; among the species studied, IEF generally resolved two or more isozymes per Skdh-1 allele present, while zone electrophoresis resolved only one.

Alcohol Oxidoreductases↗
PubMed1987

Genetic control of NADH dehydrogenase-1 and aromatic alcohol dehydrogenase-2 in hexaploid wheat.

The genetic control of NADH dehydrogenase-1 (NDH-1) and aromatic alcohol dehydrogenase-2 (AADH-2) was investigated in Triticum aestivum cv. Chinese Spring. Evidence was obtained that NDH-1 is active as a monomer and is encoded by genes located in the p arms of the homoeologous group 4 chromosomes. The NDH-1 gene loci located in 4Ap, 4Bp, and 4Dp were designated Ndh-A1, Ndh-B1, and Ndh-D1, respectively. Aadh-A2 was previously reported to be located in 6Aq; in this study, Aadh-B2 and Aadh-D2 were localized in 6Bq and 6Dq, respectively. Alcohol dehydrogenase-1 is expressed on AADH-2 zymograms; the presence of a contaminating aliphatic alcohol in one or more reagents is suggested as the probable cause of this phenomenon.

Alcohol Oxidoreductases↗
PubMed1986

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.

Aneuploidy↗
PubMed1983

Genetic control of shikimate dehydrogenase in hexaploid wheat.

The genetics of shikimate dehydrogenase (SKDH; EC 1.1.1.25) was investigated in Triticum aestivum cv Chinese Spring (2n = 6x = 42; genomic formula ABD) using the zymogram technique. The enzyme occurs in two electrophoretically distinct forms on starch gels. The results of a study of aneuploid derivatives of Chinese Spring indicate that the SKDH isozyme of faster electrophoretic mobility is encoded by a gene, designated Skdh-A1, located in the p (= short) arm of chromosome 5A and that the products of two other genes, designated Skdh-B1 and Skdh-D1, located one each in the p arms of homoeologous chromosomes 5B and 5D, respectively, encode two isozymes of slower and coincident electrophoretic mobility. Additional evidence for this interpretation of the genetic basis of hexaploid wheat SKDH was obtained in studies of the SKDH zymogram phenotypes of various close relatives of hexaploid wheat, including T. monococcum, T. longissimum, T. tauschii, T. turgidum, and T. timopheevii.

Alcohol Oxidoreductases↗
PubMed1983

Genetics and evolution of multilocus isozymes in hexaploid wheat.

Aneuploid genetic studies of isozyme variation in cv Chinese Spring have disclosed that numerous enzymes of hexaploid wheat exist in multiple molecular forms as a direct consequence of polyploidy. Sixty-nine isozyme structural genes have been identified to date. Two of these belong to a duplicate set and at least 54 to triplicate sets of paralogous genes that are located one each in related chromosomes in different genomes. Each of these gene sets encodes either two or three isozymes. The role of regional gene duplication in the production of multilocus isozymes in hexaploid wheat is as yet poorly understood, although a considerable amount of indirect evidence suggests that a large number of isozymes are encoded by genes that were produced by ancient regional gene duplication events in a genome ancestral to the genomes now present in the species. A full assessment of the role of regional gene duplication in the production of hexaploid wheat isozymes must await further studies. The isozyme structural gene locations thus far determined indicate that the gene synteny relationships that existed in the ancestral wheat genome are in large part conserved in each of the three genomes of cv Chinese Spring and that the genetic content of most individual chromosome arms has also been in large part conserved.

Biological Evolution↗
PubMed1980

Wheat Alcohol Dehydrogenase Isozymes: PURIFICATION, CHARACTERIZATION, AND GENE EXPRESSION.

Evidence in support of the hypothesis of gene expression and subunit association suggested earlier for Triticum alcohol dehydrogenase has been obtained through purification and partial characterization of the enzyme from tetraploid wheat. Three isozymes of alcohol dehydrogenase were separated and purified to apparent homogeneity using streptomycin sulfate precipitation, gel filtration chromatography, and anion exchange chromatography. The isozymes are dimers with the same molecular weight (116,000 +/- 2,000), but significantly different isoelectric pH values. The Michaelis constants for NAD(+) and ethanol are 0.1 millimolar and 12 millimolar, respectively. The substrate specificity of the three alcohol dehydrogenase isozymes was investigated.

Journal Article↗
PubMed1979

Evidence for a triplicate set of glucosephosphate isomerase structural genes in hexaploid wheat.

The glucosephosphate isomerase (GPI)zymogram phenotypes of 46 aneuploid derivatives of the cultivar Chinese Spring of hexaploid wheat were determined. Variation was observed among the strains in the relative level of expression of three GPI isozymes. The relationships observed between chromosomal constitution and zymogram phenotype support the hypothesis that the three GPI isozymes are dimers composed of protomers encoded by a minimum of three homoeologous structural genes located one each in the short arms of chromosomes 1A, 1B, and 1D. The relative levels of expression per dose of chromosome arm of the products of the three arms differ in a manner consistent with the presence of a two-fold greater quantity of the product of 1BS than of the product of 1AS and of 1DS, indicating that 1BS may contain duplicate GPI structural genes.

Chromosome Mapping↗
PubMed1976

Developmental specificity and evolution of the acid phosphatase isozymes of Triticum aestivum and its progenitor species.

The tissue and developmental specificities of the acid phosphatase (ACPH) isozymes of Triticum aestivum and its progenitor species T. turgidum and T. tauschii have been determined and compared using the zymogram technique. Tissue and/or developmental variation in relative staining intensity, suggestive of variation in the quantity of active enzyme present, was observed for each of the seven major isozymes expressed. Isozymes homologous to each of the major isozymes of the hexaploid were detected in one or the other of the progenitor species. No difference in the pattern of developmental or tissue specificity was observed between the species for any isozyme. However, ACPH-4, encoded by ACph4, a structural gene linked to chromosome 4A, differs in electrophoretic mobility between T. aestivum and T. turgidum, indicating that divergence has occurred between these species at the Acph4 locus since the origin of the hexaploid. The molecular weight of each of five ACPH isozymes of the hexaploid was determined to be approximately 58,000. This finding, plus the results of the developmental study and the earlier demonstration that the structural genes for six isozymes (includinomosomes, provides evidence in support of the suggestion that the ACPH structural genes of hexaploid wheat are homoeologous related.

Acid Phosphatase↗