Horizontal Gene Acquisitions, Mobile Element Proliferation, And Genome Decay In The Host-Restricted Plant Pathogen Erwinia Tracheiphila, Lori R. Shapiro, Erin D. Scully, Timothy J. Straub, Jihye Park, Andrew G. Stephenson, Gwyn A. Beattie, Mark L. Gleason, Roberto Kolter, Miguel C. Coelho, Consuelo M. De Moraes, Mark C. Mescher, Olga Zhaxybayeva
Modern industrial agriculture depends on high-density cultivation of genetically similar crop plants, creating favorable conditions for the emergence of novel pathogens with increased fitness in managed compared with ecologically intact settings. Here, we present the genome sequence of six strains of the cucurbit bacterial wilt pathogen Erwinia tracheiphila (Enterobacteriaceae) isolated from infected squash plants in New York, Pennsylvania, Kentucky, and Michigan. These genomes exhibit a high proportion of recent horizontal gene acquisitions, invasion and remarkable amplification of mobile genetic elements, and pseudogenization of approximately 20% of the coding sequences. These genome attributes indicate that E. tracheiphila recently emerged as a ...
Comparative Evolutionary Analysis Of Organellar Genomic Diversity In Green Plants, 2016 University of Nebraska - Lincoln
Comparative Evolutionary Analysis Of Organellar Genomic Diversity In Green Plants, Weishu Fan
Theses, Dissertations, and Student Research in Agronomy and Horticulture
The mitochondrial genome (mitogenome) and plastid genome (plastome) of plants vary immensely in genome size and gene content. They have also developed several eccentric features, such as the preference for horizontal gene transfer of mitochondrial genes, the reduction of the plastome in non-photosynthetic plants, and variable amounts of RNA editing affecting both genomes. Different organismal lifestyles can partially account for the highly diverse organellar genomes across the tree of green plants. For example, endosymbiotic and parasitic lifestyles can dramatically affect the genomic architectures of plant mitochondria and plastids. In this study, the organellar genomes of several green plants with atypical ...
Multicellular Secretory Trichome Development On Soybean And Related Glycine Gynoecia, 2016 Iowa State University
Multicellular Secretory Trichome Development On Soybean And Related Glycine Gynoecia, R. A. Healy, R. G. Palmer, Harry T. Horner
Multicellular glandular trichomes form on gynoecia of wild annual Glycine species, annual soybean cultivars, and wild perennial Glycine species. These trichomes occur from the ovary base to the style base and, in perennial species, along the style as well.Trichomes form at least 2 d before anthesis, and new trichomes develop throughout flowering and also on young seed pods. Trichome structure is similar in all taxa examined, usually five to seven linearly arranged cells. Stalk cells with callose walls become highly vacuolate, and their cytoplasms have reduced numbers of Golgi bodies and endoplasmic reticulum. During secretion, two to four distal ...
Structural Adaptations In Overwintering Leaves Of Thermonastic And Nonthermonastic Rhododendron Species, 2016 Iowa State University
Structural Adaptations In Overwintering Leaves Of Thermonastic And Nonthermonastic Rhododendron Species, Xiang Wang, Rajeev Arora, Harry T. Horner, Stephen L. Krebs
Evergreen rhododendrons (Rhododendron L.) are important woody landscape plants in many temperate zones. During winters, leaves of these plants frequently are exposed to a combination of cold temperatures, high radiation, and reduced photosynthetic activity, conditions that render them vulnerable to photooxidative damage. In addition, these plants are shallow-rooted and thus susceptible to leaf desiccation when soils are frozen. In this study, the potential adaptive significance of leaf morphology and anatomy in two contrasting Rhododendron species was investigated. R. catawbiense Michx. (native to eastern United States) exhibits thermonasty (leaf drooping and curling at subfreezing temperatures) and is more winter-hardy [leaf freezing ...
The Genetics, Pathology, And Molecular Biology Of T-Cytoplasm Male Sterility In Maize, 2016 United States Department of Agriculture
The Genetics, Pathology, And Molecular Biology Of T-Cytoplasm Male Sterility In Maize, Roger P. Wise, Charlotte R. Bronson, Patrick S. Schnable, Harry T. Horner
This chapter reviews the genetics, pathology, and molecular biology of T-cytoplasm male sterility in maize. The chapter discusses the role of cytoplasmic male sterility systems in facilitating the production of hybrid seeds. The effects of widespread planting of T-cytoplasm maize on the severe 1970 epidemic and effect of a mitochondria1 gene on disease susceptibility and male sterility are discussed. It also discusses the involvement of nuclear cytoplasmic interactions in restoration of cms-T, the perspectives of cms-T researchers, and future directions. In cms-T plants, male sterility is associated with premature breakdown of the mitochondria-rich, tapetal cell layer of the anther; this ...
Seed-Set Evaluation Of Four Male-Sterile, Female-Fertile Soybean Lines Using Alfalfa Leafcutting Bees And Honey Bees As Pollinators, E. Ortiz-Perez, R. M. Mian, R. L. Cooper, T. Mendiola, T. Tew, Harry T. Horner, S. J. Hanlin, R. G. Palmer
Male-sterile, female-fertile plants were used to produce hybrid soybean seed. Manual cross-pollination using male-sterile plants to produce large quantities of hybrid seed is difficult and time-consuming because of the low success rate in cross-pollination. Insect pollinators may be suitable vectors to transfer pollen, but the most suitable vector for pollen transfer from the male parent to the female parent has not been identified for soybean. The objective of the present study was to evaluate seed-set on four male-sterile, female-fertile soybean lines by using alfalfa leafcutting bees (Megachile rotundata (F.)) and honey bees (Apis mellifera (L.)) as pollinators. Seed-set was evaluated ...
Formation Of Calcium Oxalate Crystals Associated With Apothecia Of The Discomycete Dasyscypha Capitata, 2016 Iowa State University
Formation Of Calcium Oxalate Crystals Associated With Apothecia Of The Discomycete Dasyscypha Capitata, Harry T. Horner, Lois H. Tiffany, Anita M. Cody
Calcium oxalate dihydrate crystals form at or near the tips of sterile hairs on the apothecia of the oak leaf litter discomycete Dasyscypha capitata. Early in their development, the crystals appear to be covered by a wall or membrane, whereas later they appear external. The crystals on each hair form a mass of crystals called a druse. Quite often the smaller crystals near the apex of the tip form a rosette, whereas the more peripheral crystals are much larger and display shapes possibly related to environmental factors. The formation and development of Dasyscypha crystals are compared with recent studies of ...
Formation Of Elongated Starch Granules In High-Amylose Maize, 2016 Iowa State University
Formation Of Elongated Starch Granules In High-Amylose Maize, Hongxin Jiang, Harry T. Horner, Tracey M. Pepper, Michael Blanco, Mark Campbell, Jay-Lin Jane
GEMS-0067 maize starch contains up to 32% elongated starch granules, much higher than amylose-extender (ae) single-mutant maize starch (∼7%) and normal (non-mutant) maize starch (0%). These elongated granules are highly resistant to enzymatic hydrolysis at 95–100 °C, which function as resistant starch. The structure and formation of these elongated starch granules, however, were not known. In this study, light, confocal laser-scanning, scanning electron, and transmission electron microscopy were used to reveal the structure and formation of these elongated starch granules. The transmission electron micrographs showed fusion through amylose interaction between adjacent small granules in the amyloplast at the early ...
Early Endosperm, Embryo, And Ovule Development In Glycine Max (L.) Merr., 2016 Iowa State University
Early Endosperm, Embryo, And Ovule Development In Glycine Max (L.) Merr., Mark A. Chamberlin, Harry T. Horner, Reid G. Palmer
Anatomical and ultrastructural aspects of soybean embryo, endosperm, and ovule development are described for the zygote to late heart-shaped embryo stages (0-35 d postfertilization). Nucellar cells subtending the degenerative synergid break down, allowing for pollen tube passage to this synergid. In 15 of 17 ovules studied, the degenerative synergid occupies a position abfunicular to the zygote. The inner integument differentiates into the endothelium and exterior layers of thick-walled cells at the globular embryo stage. The endothelium has a cuticle on its inner surface that begins to fragment at the onset of endosperm cellularization. Cellularization of the free-nuclear endosperm is initiated ...
Floral Nectary Fine Structure And Development In Glycine Max L. (Fabaceae), 2016 Iowa State University
Floral Nectary Fine Structure And Development In Glycine Max L. (Fabaceae), Harry T. Horner, Rosaria A. Healy, Teresa Cervantes-Martinez, Reid G. Palmer
Floral nectaries of annual cultivated Glycine max develop between the bases of the central gynoecium and lateral stamen ring. Each discoid nectary forms immediately before flower opening and degenerates within 24 h. Three stages of nectary development are identified: preactive, active, and postactive. Preactive and active nectaries are composed of a single-layered epidermis that contains many open stomata, with guard cells having thickened walls, starch-engorged plastids, and other organelles. The major portion of each nectary consists of thin-walled special parenchyma cells, each having dense cytoplasm with a nucleus, Golgi bodies and vesicles, mitochondria, plastids, endoplasmic reticulum, many ribosomes, and one ...
A Microscopic Study Of The Trichomes On Gynoecia Of Normal And Tetraploid Clark Cultivars Of Glycine Max And Seven Near Isogenic Lines, Rosaria A. Healy, Harry T. Horner, Theodore B. Bailey, Reid G. Palmer
The surfaces of gynoecia of Glycine max cultivars—normal Clark, a tetraploid Clark, and seven isolines—display variations in at least three types of trichomes. The normal Clark soybean gynoecium has at least three and possibly four types of trichomes: a two‐ to four‐celled, elongate, thick‐walled trichome (TWT), an elongate thin‐walled unicellular trichome (UCT), a secretory multicellular trichome (MCT), and an elongate thin‐walled bicellular trichome that we have interpreted as an immature TWT. All these types are present on the gynoecium by 1 d before anthesis. After fertilization, the UCT is rare, but the other types ...
Analysis And Mapping Of Gene Families Encoding Β-1,3-Glucanases Of Soybean, 2016 Iowa State University
Analysis And Mapping Of Gene Families Encoding Β-1,3-Glucanases Of Soybean, Wei Jin, Harry T. Horner, Reid G. Palmer, Randy C. Shoemaker
Oligonucleotide primers designed for conserved sequences from coding regions of β-1,3-glucanase genes from different species were used to amplify related sequences from soybean [Glycine max (L.) Merr.]. Sequencing and cross-hybridization of amplification products indicated that at least 12 classes of β-1,3-glucanase genes exist in the soybean. Members of classes mapped to 34 loci on five different linkage groups using an F2 population of 56 individuals. β-1,3-Glucanase genes are clustered onto regions of five linkage groups. Data suggest that more closely related genes are clustered together on one linkage group or on duplicated regions of linkage groups. Northern ...
Evolution And Systematic Value Of Leaf Crystal Macropatterns In The Genus Peperomia (Piperaceae), 2016 Iowa State University
Evolution And Systematic Value Of Leaf Crystal Macropatterns In The Genus Peperomia (Piperaceae), Harry T. Horner, Stefan Wanke, Marie-Stephanie Samain
Leaves of Peperomia species vary in texture, shape, succulence, lamina size, thickness, coloration, and venation. Each leaf contains only calcium oxalate druses in palisade cells, druses in palisade and raphides in spongy parenchyma, or druses in palisade and prisms in spongy parenchyma. Collectively, these variations create distinct crystal macropatterns. Leaves from 45 species were studied to identify their macropatterns and to compare the macropatterns with molecular data. Microscopic data showed two major crystal macropatterns and five variations of them. All but one species displayed either a single druse in most palisade cells forming one or more uniform crystal layers (81 ...
Insect-Mediated Cross-Pollination In Soybean [Glycine Max (L.) Merrill]: Ii. Phenotypic Recurrent Selection, 2016 Universidad Autonoma de Nuevo Leon
Insect-Mediated Cross-Pollination In Soybean [Glycine Max (L.) Merrill]: Ii. Phenotypic Recurrent Selection, Evelyn Ortiz-Perez, Hunt Wiley, Harry T. Horner, William H. Davis, Reid G. Palmer
Recurrent selection is a method for population improvement which has been used in soybean [Glycine max (L.) Merrill] to modify traits such as grain yield, seed-protein content, seed-oil content, tolerance to iron-deficiency chlorosis, and seed size. Nuclear male-sterility with insect-mediated cross-pollination has been successfully used in recurrent selection schemes in soybean. However, little attention has been given to selection to increase the agronomic performance of male-sterile plants per se. The objective of this study was to evaluate the response of male-sterile lines segregating for male-sterile alleles ms2, ms3, ms6, ms8, and ms9 to phenotypic recurrent selection for increased seed-set after ...
Mechanisms Of Genic Male Sterility, 2016 Iowa State University
Mechanisms Of Genic Male Sterility, Harry T. Horner, Reid G. Palmer
For normal sexual reproductive development, coordination must occur between both male and female organ ontogeny. An abnormality at any point in this process may lead to sterility. Classification of sterility can be divided into heritable and nonheritable sterility. Numerous schemes for mechanisms controlled by nuclear genes (genic male sterility) have been devised to identify the timing and location of the inception of sterility. These schemes are divided into structural (gross organ changes) and functional. The latter may be divided into abnormal changes occurring in the male cells or surrounding anther tissues during microsporogenesis. Even though sterility can be produced by ...
Macropattern Of Styloid And Druse Crystals In Quillaja (Quillajaceae) Bark And Leaves, 2016 Iowa State University
Macropattern Of Styloid And Druse Crystals In Quillaja (Quillajaceae) Bark And Leaves, Nels R. Lersten, Harry T. Horner
Quillaja has been shuffled among tribes and subfamilies of Rosaceae, segregated from it as a separate family, and, most recently, transferred to the Fabales as a separate family. Many anomalous characters have kept it from being settled anywhere permanently. One character never mentioned by systematists, but long known, is the anomalous (for Rosaceae) occurrence of prominent styloid calcium oxalate crystals, reported from the inner bark of stems. We describe in more detail the macropattern of crystal distribution in stem and leaf, using vibratome sections, sodium hypochlorite clearings of leaves, and polarizing and scanning electron microscopy. Styloids are extremely numerous in ...
Histological Features Of Anthers From Normal And Ms3 Mutant Soybean, 2016 Hokkaido University
Histological Features Of Anthers From Normal And Ms3 Mutant Soybean, H. Nakashima, Harry T. Horner, R. G. Palmer
Anthers of male-sterile mutant (ms3) and normal soybean [Glycine max (L.) Merr.] were compared by using a triple-staining procedure for DNA, polysaccharides and proteins, and a single-staining procedure for sporopollenin in conjunction with brightfield and fluorescent microscopy. The purpose of this study was to determine at what stage of anther development histological differences were detectable between male-sterile (ms3) and normal soybean. At the tetrad stage, a prominent greenish-blue material, visible with the triple-staining procedure, filled some of the enlarged tapetal cells of anthers of ms3 plants. This material was also autofluorescent and had an affinity for the ...
Insect-Mediated Seed-Set Evaluation Of 21 Soybean Lines Segregating For Male Sterility At 10 Different Loci, 2016 Iowa State University
Insect-Mediated Seed-Set Evaluation Of 21 Soybean Lines Segregating For Male Sterility At 10 Different Loci, E. Ortiz-Perez, Harry T. Horner, S. J. Hanlin, R. G. Palmer
The first requirement to establish a successful hybrid soybean program is the availability of a stable male-sterile, female-fertile system. Male sterility has been an important tool in soybean breeding programs to improve traits such as yield, seed-protein and seed-oil content, and seed size. However, improvement of seed-set per se on male-sterile plants has not been an important breeding objective. The evaluation of the out-crossing potential of the available male-sterile, female-fertile soybean lines is crucial to determine the future of hybrid soybean. The objective of this study was to evaluate seed-set among 21 soybean lines segregating for male sterility at 10 ...
Calcium Oxalate Crystals In Developing Seeds Of Soybean, 2016 Ankara University
Calcium Oxalate Crystals In Developing Seeds Of Soybean, H. Ilarslan, R. G. Palmer, Harry T. Horner
Young developing soybean seeds contain relatively large amounts of calcium oxalate (CaOx) monohydrate crystals. A test for Ca and CaOx indicated that Ca deposits and crystals initially occurred in the funiculus, where a single vascular bundle enters the seed. Crystals formed in the integuments until the embryo enlarged enough to crush the inner portion of the inner integument. Crystals then appeared in the developing cotyledon tissues and embryo axis. All crystals formed in cell vacuoles. Dense bodies and membrane complexes were evident in the funiculus. In the inner integument, cell vacuoles assumed the shape of the future crystals. This presumed ...
The Phenolic Monoterpenoid Carvacrol Inhibits The Binding Of Nicotine To The Housefly Nicotinic Acetylcholine Receptor, Fan Tong, Aaron D. Gross, Marc C. Dolan, Joel R. Coats
Joel R. Coats
The phenolic monoterpenoid carvacrol, which is found in many plant essential oils (thyme, oregano and Alaska yellow cedar), is highly active against pest arthropods, but its mechanisms of action are not fully understood. Here, carvacrol is shown to bind in a membrane preparation containing insect nicotinic acetylcholine receptors (nAChRs). [14C]-Nicotine binding assays with Musca domestica (housefly) nAChRs were used in this study to demonstrate carvacrol's binding to nAChRs, thereby acting as a modulator of the receptors.
Carvacrol showed a concentration-dependent inhibition of [14C]-nicotine binding in a membrane preparation of housefly heads containing nAChRs ...