Matching Items (4)

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Analysis of Genetic Diversity and Clarification of Species Boundaries in Echinomastus erectocentrus var. acunensis and Close Relatives

Description

Echinomastus erectocentrus (J.M. Coulter) Britton & Rose var. acunensis (W.T. Marshall) Bravo, the Acuña cactus, is a small, single-stemmed spherical cactus with a restricted distribution across the Sonoran Desert in

Echinomastus erectocentrus (J.M. Coulter) Britton & Rose var. acunensis (W.T. Marshall) Bravo, the Acuña cactus, is a small, single-stemmed spherical cactus with a restricted distribution across the Sonoran Desert in southern Arizona and into northern Sonora, Mexico. Populations of E. erectocentrus var. acunensis are threatened by loss of habitat, climate change, predation, and border related impacts. Due to the severity of these threats and shrinking population sizes, E. erectocentrus var. acunensis was federally listed as endangered by the United States Fish and Wildlife Service in 2013. The varieties of Echinomastus erectocentrus, E. erectocentrus var. acunensis and E. erectocentrus var. erectocentrus (J.M. Coulter) Britton & Rose, share many morphological characteristics that make them difficult to distinguish from one another. Echinomastus johnsonii (Parry ex Engelm.) E.M. Baxter, a presumed closely related species, also has a high level of morphological overlap that further complicates our understanding of species boundaries and detailed morphological data for these three taxa indicate a geographical cline. The goal of this project is to document the genetic diversity within and among populations of E. erectocentrus var. acunensis, and its close relatives E. erectocentrus var. erectocentrus and E. johnsonii. To accomplish this, populations of E. erectocentrus var. acunensis, E. erectocentrus var. erectocentrus, E. johnsonii and the outgroup Echinomastus intertextus (Engelm.) Britton & Rose were sampled. Deoxyribonucleic acid (DNA) was extracted, and data were collected for nine microsatellite regions developed specifically for these taxa, and two microsatellite regions developed for Sclerocactus, a closely related genus. Standard population genetic measures were used to determine genetic variation and structure, and this observed genetic differentiation was then compared to the current morphological understanding of the group. These analyses help improve the knowledge of the genetic structure of E. erectocentrus var. acunensis and inform the understanding of species boundaries and evolutionary relationships within the group by revealing genetic distinctiveness between all four taxa and hybrid populations between the two varieties. This information also reveals patterns of gene flow and population locations that have the highest conservation priority, which can be incorporated into efforts to conserve and protect this endangered species.

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Created

Date Created
  • 2020

Membrane specificity of proton pyrophosphatase and plasmodesmata ultrastructure provide the structural basis for sugar loading in Oryza sativa and Physcomitrella patens

Description

The remarkable conservation of molecular and intra-/inter-cellular pathways underpinning the fundamental aspects of sugar partitioning in two evolutionarily divergent organisms – a non-vascular moss Physcomitrella patens and a vascular cereal

The remarkable conservation of molecular and intra-/inter-cellular pathways underpinning the fundamental aspects of sugar partitioning in two evolutionarily divergent organisms – a non-vascular moss Physcomitrella patens and a vascular cereal crop Oryza sativa (rice) – forms the basis of this manuscript. Much of our current knowledge pertaining to sugar partitioning in plants mainly comes from studies in thale cress, Arabidopsis thaliana, but how photosynthetic sugar is loaded into the phloem in a crop as important as rice is still debated. Even less is known about the mechanistic aspects of sugar movement in mosses. In plants, sugar either moves passively via intercellular channels called plasmodesmata, or through the cell wall spaces in an energy-consuming process. As such, I first investigated the structure of plasmodesmata in rice leaf minor vein using electron tomography to create as of yet unreported 3D models of these channels in both simple and branched conformations. Contrary to generally held belief, I report two different 3D morphotypes of simple plasmodesmata in rice. Furthermore, the complementary body of evidence in arabidopsis implicates plasma membrane localized Proton Pyrophosphatase (H+-PPase) in the energy-dependent movement of sugar. Within this wider purview, I studied the in situ ultrastructural localization patterns of H+-PPase orthologs in high-pressure frozen tissues of rice and physcomitrella. Were H+-PPases neo-functionalized in the vascular tissues of higher plants? Or are there evolutionarily conserved roles of this protein that transcend the phylogenetic diversity of land plants? I show that H+-PPases are distinctly expressed in the actively growing regions of both rice and physcomitrella. As expected, H+-PPases were also localized in the vascular tissues of rice. But surprisingly, H+-PPase orthologs were also prominently expressed at the gametophyte-sporophyte junction of physcomitrella. Upon immunogold labeling, H+-PPases were found to be predominantly localized at the plasma membrane of the phloem complexes of rice source leaves, and both the vacuoles and plasma membrane of the transfer cells in the physcomitrella haustorium, linking H+-PPases in active sucrose loading in both plants. As such, these findings suggest that the localization and presumably the function of H+-PPases are conserved throughout the evolutionary history of land plants.

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Date Created
  • 2016

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A phylogenetic study of the plant family Martyniaceae (order Lamiales)

Description

Acceptance of the plant group Martyniaceae as a distinct family has long been questioned. Previously placed in the family Pedaliaceae, the Martyniaceae have been allied to numerous other families within

Acceptance of the plant group Martyniaceae as a distinct family has long been questioned. Previously placed in the family Pedaliaceae, the Martyniaceae have been allied to numerous other families within the order Lamiales. The objectives of this study include the investigation of the placement of the Martyniaceae within the order Lamiales using molecular data (chloroplast DNA sequences), the further examination of the internal relationships of the Martyniaceae using an expanded nuclear and chloroplast sequences data set, and the construction of a taxonomic treatment of the family that includes all published names and taxa in the Martyniaceae. An analysis of the Lamiales using two chloroplast gene regions (ndhF and rps16) reveals that the Martyniaceae should be segregated from the family Pedaliaceae, but is not able to support the placement of any of its putatively-related families as sister to the Martyniaceae. Sequences from 151 taxa of the Lamiales are included in the analysis, including six representatives from the Martyniaceae. An analysis of the Martyniaceae using three chloroplast gene regions (psbA-trnH spacer, trnQ-5'rps16 intergenic spacer, and trnS-trnG-trnG spacer and intron) and the Internal Transcribed Spacer resolves two major clades within the Martyniaceae corresponding to the North American taxa (Martynia and Proboscidea) and the South American taxa (Craniolaria, Holoregmia, and Ibicella). Sequences from all five genera and 15 taxa were included in the analysis. Results from the molecular phylogenetic analyses are incorporated into a revised taxonomic treatment of the family. Five genera and thirteen species are recognized for the family Martyniaceae.

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Created

Date Created
  • 2011

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Cyclocarya brownii from the Paleocene of North Dakota, USA

Description

The Juglandaceae (walnuts, hickories, pecans) has one of the best-documented fossil records in the Northern Hemisphere. The oldest modern genus, Cyclocarya, today restricted to China, first appears in the late

The Juglandaceae (walnuts, hickories, pecans) has one of the best-documented fossil records in the Northern Hemisphere. The oldest modern genus, Cyclocarya, today restricted to China, first appears in the late Paleocene (57 ma) of North Dakota, USA. Unlike walnuts and pecans that produce edible fruits dispersed by mammals, Cyclocarya fruits are small nutlets surrounded by a prominent circular wing, and are thought to be wind- or water-dispersed. The current study provides the first evidence that fossil fruits were different from modern forms in the number and organization of their attachment to reproductive branches, and in their anatomical structure. Unlike the modern genus that bears separate pistillate and staminate flowers the fossil fruits had attached pollen-bearing structures. Unisexual pollen catkins are also present, suggesting the fossil Cyclocarya may have differed from its modern relative in this feature. Like several other plants from the late Paleocene Almont/Beicegel Creek floras, Cyclocarya shows a mosaic combination of characters not seen in their modern counterparts. Fossils were collected from the field, and examined for specimens exposed on the weathered rock surface. Specimens from Almont were photographed with reflected light, while those from Beicegel Creek cut into slabs and prepared by etching the rock matrix in 49% hydrofluoric and re-embedding the exposed plant material in cellulose acetate and acetone to make "peels". Selected specimens are cut out, mounted on microscope slides, and studied with light microscopy. These fossil fruits were studied because they are the earliest fossil evidence of Cyclocarya. They are exceptionally preserved and thus provide critical structural evidence for changes in that occurred during the evolution of plants within this lineage. Because Cyclocarya fruits are winged, they might be assumed to be wind-dispersed. Their radial symmetry does not have the aerodynamic qualities typical of wind-dispersed fruits, and may have been dispersed by water.

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Date Created
  • 2010