Mary O'Connell
New Mexico State University
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Theoretical and Applied Genetics | 2003
Eyal Blum; Michael Mazourek; Mary O'Connell; Jeanne Curry; Troy Thorup; Kede Liu; Molly Jahn; Ilan Paran
Quantitative variation in the accumulation of two major capsaicinoids responsible for pungency in the fruit of chile peppers, capsaicin and dihydrocapsaicin, was analyzed in a cross between the non-pungent Capsicum annuum parent cv. Maor and a pungent Capsicum frutescens parent, accession BG 2816. In order to identify quantitative trait loci (QTLs) for capsaicinoid content, we employed the bulked segregant analysis method and screened bulked DNA from F2 individuals at the extremes of the distribution of capsaicinoid content with RAPD primers. Screening with 400 primers allowed the identification of three loci that were polymorphic between the bulks. These RAPD markers were converted to SCARs and subsequently mapped with additional RFLP markers to chromosome 7 of pepper. QTL interval analysis for individual and total capsaicinoid content identified a major QTL, termed cap, which explained 34–38% of the phenotypic variation for this trait in two growing environments. For all measurements, the allele of the pungent parent BG 2816 at cap contributed to the increased level of pungency. To determine whether known structural genes in the pathway could define a candidate for this QTL, 12 clones obtained from differentially expressed transcripts from placental tissue in pungent peppers were also mapped. None of them had a significant effect on this trait, nor did the allelic state at the locus C, the on/off switch for pungency in pepper, located on chromosome 2. The identity of cap and its effect on capsaicin content in other backgrounds will be addressed in future studies.
Plant Physiology | 1993
Tracy L. Kahn; Susan E. Fender; Elizabeth A. Bray; Mary O'Connell
A number of genes are induced by drought stress, and some of these genes are regulated by the plant hormone abscisic acid (ABA). In tomato (Lycopersicon esculentum), four genes have been identified and isolated that require elevated levels of endogenous ABA for expression: le4, le16, le20, and le25. To gain a better understanding of the role of these genes during stress, their expression has been studied in the drought-resistant relative of tomato, Lycopersicon pennellii. It was determined that homologous genes to all four of the L. esculentum genes were present in the L. pennellii genome. Studies were undertaken to compare the expression characteristics of these genes in L. esculentum, L. pennellii, and their F1. Using two methods of water-deficit imposition, whole plants to which water was withheld and detached leaves that were wilted to 88% of their original fresh weight, it was demonstrated that transcripts of these genes accumulated in L. pennellii in response to water deficit. In general, the increase occurred after a longer period of water deficit in L. pennellii than in tomato. As in drought-sensitive species, ABA levels were elevated by drought stress in L. pennellii, although the levels were reduced compared with those in tomato. All four tomato genes were responsive to ABA in L. esculentum and the F1, but only three of the four genes (le16, le20, and le25) were induced in response to exogenous application of ABA in L. pennellii. The patterns of expression of these genes in L. pennellii are generally similar to that of L esculentum; therefore, it is suggested that these genes play a similar, yet undefined, role in both genotypes rather than being genes that are responsible for the greater drought resistance of L. pennellii.
Theoretical and Applied Genetics | 1986
Mary O'Connell; Maureen R. Hanson
SummaryA single somatic hybrid callus clone was identified following the fusion of Lycopersicon esculentum protoplasts and Solanum rickii suspension culture protoplasts. The hybrid nature of the callus and the plants regenerating from it was determined by assaying phosphoglucomutase-2 isozyme expression. The chloroplast genome present in four somatic hybrid plants was characterized by probing digests of total DNA with nick translated L. esculentum chloroplast DNA(cpDNA). All four somatic hybrid plants had inherited S. rickii cpDNA. Two clones of plant mitochondrial DNA (mtDNA), soybean 18S and 5S rDNA and maize cytochrome oxidase subunit II were used to characterize the mtDNA present in total DNA digests of four somatic hybrid plants. In both cases, the somatic hybrid plants had inherited most but not all of the S. rickii specific fragments, but none of the L. esculentum specific fragments.
Plant Molecular Biology | 1996
Tao Wei; Mary O'Connell
A drought- and abscisic acid (ABA)-inducible gene, His1, was isolated from Lycopersicon pennellii, a drought-resistant relative of cultivated tomato, and the gene structure was defined experimentally. The nucleotide sequence of His1 predicts a protein of 202 amino acid residues, with a significant sequence homology to plant H1 histones. Consensus sequences for both H1 histone-specific promoter elements as well as an ABA-responsive element were identified in the 5′-flanking region of His1. Transcripts of this gene accumulate in leaf tissue in response to drought in three tomato species including cultivated tomato (L. esculentum), L. pennellii, and L. chilense, as well as in tobacco. Transcripts for His1 are constitutively expressed in roots; transcript abundances in tomato root tips were equivalent to transcript abundances in more mature regions of the seedling root. The accumulation in leaves of transcripts for His1 preceded visible symptoms of drought stress in the plants. Transcript accumulation was detected in both drought-sensitive and drought-resistant species at similar leaf water potentials, 255-1 −1.3 to −1.4 MPa.
Theoretical and Applied Genetics | 1992
J.M. Melzer; Mary O'Connell
SummaryAsymmetric somatic hybrids were recovered following fusion of tomato leaf mesophyll protoplasts with irradiated protoplasts isolated from Lycopersicon pennellii suspension cells. The asymmetry was determined by scoring the regenerants at between 20 and 24 loci using isozymes and restriction fragment length polymorphisms. In addition, three quantitative traits, fruit size, leaf shape, and stigma exsertion, were measured in the regenerants. The recovery of asymmetric somatic hybrids was as high as 50% of the regenerants, and there was no requirement for the transfer of a selectable marker gene from the irradiated partner. The amount of nuclear DNA transferred from the irradiated protoplast fusion partner was found to be inversely proportional to the radiation dose. It was possible to recover tomato asymmetric somatic hybrids which were self-fertile and contained limited amounts of genetic information from L. pennelli.
Euphytica | 1994
Anne-Marie A. Wolters; E. Jacobsen; Mary O'Connell; Guusie Bonnema; K. Sree Ramulu; Hans de Jong; Herman Schoenmakers; Jelle Wijbrandi; Maarten Koornneef
Protoplast fusion can be used to produce somatic hybrids of species that cannot be obtained by sexual hybridization. The possibility to introgress genes from Solanum species into the cultivated tomato species Lycopersicon esculentum, and to obtain novel cytoplasm-nucleus combinations (cybrids) was considered as an important strategy to extend the genetic variation available for tomato breeding. Somatic hybrids between L. esculentum and other Lycopersicon species, as well as between L. esculentum and Solanum or Nicotiana species, have been produced. Specific mutants, genotypes with antibiotic resistances, and metabolic inhibition by iodoacetate or iodoacetamide and irradiation were used for the selection of hybrids. In addition, the improvement of protoplast culture techniques and the use of the favourable tissue culture traits derived from species such as L. peruvianum, which have been introduced into tomato by classical breeding, allowed the efficient recovery of somatic hybrids. However, the occurrence of somatic incongruity in fusion combinations of L. esculentum and Solanum and even more in L. esculentum and Nicotiana, did not allow the production of true cybrids and/or fertile hybrids, indicating the importance of both cytoplasm-nucleus and nucleus-nucleus interactions in somatic incongruity. Another problem with fusions between distantly related species is the strongly reduced fertility of the hybrids and the very limited homoeologous recombination between chromosomes of the parental species. Partial genome transfer from donor to recipient through microprotoplast (+) protoplast fusion, and the production of monosomic or disomic chromosome addition lines, light overcome some of these problems. In symmetric somatic hybrids between L. esculentum and S. tuberosum the occurrence of limited somatic and meiotic recombination was demonstrated. Fertile progeny plants could be obtained, though at a low frequency, when embryo rescue was performed on a large scale after backcrossing hexaploid somatic tomato (+) potato hybrids with a tetraploid potato genotype. The potential value of genomic in situ hybridization (GISH) and RFLPs for the analysis of the genome/chromosome composition of the hybrids has been demonstrated for intergeneric somatic hybrids between Lycopersicon and Solanum.
Plant Cell Reports | 1989
Susan E. Fender; Mary O'Connell
The expression of heat shock proteins (HSPs) was compared between genetically characterized heat tolerant and heat sensitive lines of cotton (Gossypium hirsutum andG. barbadense) using electrophoretic analysis ofin vivo labelled proteins. No differences were observed between the two lines with regard to: the temperature at which HSP synthesis was induced (37°C); the temperature at which HSP synthesis was maximal (45°C); the rates of recovery from HSP synthesis; the duration of HSP synthesis; or the major size classes of HSPs expressed in these two lines. Several HSPs were identified on 2D gels which were expressed uniquely in either the tolerant or sensitive cotton line. However, the HSP pattern displayed in a heat tolerant BC-3 individual was that of the heat sensitive parent.
Theoretical and Applied Genetics | 1987
Mary O'Connell; Maureen R. Hanson
SummarySomatic hybrid plants have been regenerated following polyethylene glycol mediated fusion of leaf mesophyll protoplasts from tomato and protoplasts from Lycopersicon pennellii callus. Three different cultivars of tomato were used as sources of protoplasts: Early Girl, Manapal, and UC82B. Fusions were performed between protoplasts of these tomato cultivars and protoplasts of L. pennellii, and between protoplasts of the cultivars and protoplasts of L. pennellii that had been exposed to 3 or 6 krads of gamma radiation. Somatic hybrid plants were identified on the basis of heterozygous isozyme banding patterns, and leaf and flower morphology. Somatic hybrid plants were regenerated following fusion of tomato protoplasts with either untreated or irradiated L. pennellii protoplasts. All were heterozygous for isozyme loci on five different chromosomes. Regenerated somatic hybrids showed inheritance of either or both parental chloroplast genomes, but predominantly the L. pennellii mitochondrial genome. The regenerated somatic hybrid plants exhibited reduced fertility, less than 20% viable pollen. A total of 34 somatic hybrid calli were identified. Of these, 21 regenerated shoots, and 7 produced seed following manual pollinations.
Theoretical and Applied Genetics | 1992
A.B. Bonnema; J.M. Melzer; L.W. Murray; Mary O'Connell
SummaryThe organization of the mitochondrial genome and the genotype of the chloroplast genome was characterized using restriction fragment length polymorphisms in a population (82 individuals) of symmetric and asymmetric somatic hybrids of tomato. The protoplast fusion products were regenerated following the fusion of leaf mesophyll protoplasts of Lycopersicon esculentum (tomato cv ‘UC82’) with suspension cell protoplasts of L. pennellii that had been irradiated with 5, 10, 15, 25, 50, or 100 kRads from a gamma source. The chloroplast genome in the somatic hybrids showed a random pattern of inheritance, i.e., either parental genome was present in equal numbers of regenerants, while in asymmetric somatic hybrids, the chloroplast genotype reflected the predominant nuclear genotype, i.e., tomato. The mitochondrial genome in the symmetric somatic hybrids showed a non-random pattern of inheritance, i.e., predominantly from the L. pennellii parent; asymmetric somatic hybrids had more tomato-specific mitochondrial sequences than symmetric somatic hybrids. The non-random inheritance of the chloroplast and mitochondrial DNA in these tomato protoplast fusion products appears to be influenced by the nuclear background of the regenerant.
Theoretical and Applied Genetics | 1991
A.B. Bonnema; J.M. Melzer; Mary O'Connell
SummaryCybrids have been regenerated following protoplast fusion of iodoacetamide-treated leaf mesophyll cells of Lycopersion esculentum cv UC82 and gamma-irradiated cell suspensions of L. pennellii, LA716. The cybrids were recovered in the regenerant population at a frequency of 19%, no selection pressure was applied for the persistence of the donor cytoplasm. The nuclear genotype of ten cybrids was characterized extensively using isozyme markers, cDNA-based restriction fragment length polymorphisms (RFLPs), and the morphology of the plants. No nuclear genetic information from L. pennellii was detected in the cybrids. The organellar genotype of the cybrids was determined using cloned probes and species-specific RFLPs. All the cybrids had inherited the tomato chloroplast genome and had varying amounts of L. pennellii mitochondrial DNA. The cybrids all had a diploid chromosome number of 24, produced pollen, and set seed.
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University of Texas Health Science Center at San Antonio
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View shared research outputsUniversity of Texas Health Science Center at San Antonio
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