School of Botany - Research Publications
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ItemSulfate assimilation in eukaryotes: fusions, relocations and lateral transfers.(Springer Science and Business Media LLC, 2008-02-04)BACKGROUND: The sulfate assimilation pathway is present in photosynthetic organisms, fungi, and many bacteria, providing reduced sulfur for the synthesis of cysteine and methionine and a range of other metabolites. In photosynthetic eukaryotes sulfate is reduced in the plastids whereas in aplastidic eukaryotes the pathway is cytosolic. The only known exception is Euglena gracilis, where the pathway is localized in mitochondria. To obtain an insight into the evolution of the sulfate assimilation pathway in eukaryotes and relationships of the differently compartmentalized isoforms we determined the locations of the pathway in lineages for which this was unknown and performed detailed phylogenetic analyses of three enzymes involved in sulfate reduction: ATP sulfurylase (ATPS), adenosine 5'-phosphosulfate reductase (APR) and sulfite reductase (SiR). RESULTS: The inheritance of ATPS, APR and the related 3'-phosphoadenosine 5'-phosphosulfate reductase (PAPR) are remarkable, with multiple origins in the lineages that comprise the opisthokonts, different isoforms in chlorophytes and streptophytes, gene fusions with other enzymes of the pathway, evidence a eukaryote to prokaryote lateral gene transfer, changes in substrate specificity and two reversals of cellular location of host- and endosymbiont-originating enzymes. We also found that the ATPS and APR active in the mitochondria of Euglena were inherited from its secondary, green algal plastid. CONCLUSION: Our results reveal a complex history for the enzymes of the sulfate assimilation pathway. Whilst they shed light on the origin of some characterised novelties, such as a recently described novel isoform of APR from Bryophytes and the origin of the pathway active in the mitochondria of Euglenids, the many distinct and novel isoforms identified here represent an excellent resource for detailed biochemical studies of the enzyme structure/function relationships.
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ItemA Novel Family of Apicomplexan Glideosome-associated Proteins with an Inner Membrane-anchoring Role(AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2009-09-11)The phylum Apicomplexa are a group of obligate intracellular parasites responsible for a wide range of important diseases. Central to the lifecycle of these unicellular parasites is their ability to migrate through animal tissue and invade target host cells. Apicomplexan movement is generated by a unique system of gliding motility in which substrate adhesins and invasion-related proteins are pulled across the plasma membrane by an underlying actin-myosin motor. The myosins of this motor are inserted into a dual membrane layer called the inner membrane complex (IMC) that is sandwiched between the plasma membrane and an underlying cytoskeletal basket. Central to our understanding of gliding motility is the characterization of proteins residing within the IMC, but to date only a few proteins are known. We report here a novel family of six-pass transmembrane proteins, termed the GAPM family, which are highly conserved and specific to Apicomplexa. In Plasmodium falciparum and Toxoplasma gondii the GAPMs localize to the IMC where they form highly SDS-resistant oligomeric complexes. The GAPMs co-purify with the cytoskeletal alveolin proteins and also to some degree with the actin-myosin motor itself. Hence, these proteins are strong candidates for an IMC-anchoring role, either directly or indirectly tethering the motor to the cytoskeleton.
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ItemTremaux on Species: A Theory of Allopatric Speciation (and Punctuated Equilibrium) before Wagner(STAZIONE ZOOLOGICA ANTON DOHRN, 2008)Pierre Trémaux's 1865 ideas on speciation have been unjustly derided following his acceptance by Marx and rejection by Engels, and almost nobody has read his ideas in a charitable light. Here we offer an interpretation based on translating the term sol as "habitat," in order to show that Trémaux proposed a theory of allopatric speciation before Wagner and a punctuated equilibrium theory before Gould and Eldredge, and we translate the relevant discussion from the French. We believe he may have influenced Darwin's revision to the third edition of the Origin on rates of evolution. We also suggest that Gould's dismissal of Trémaux is motivated by concern that others might think punctuated equilibrium theory was tainted by a connection with Trémaux.
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ItemHeuristic and optimal solutions for set-covering problems in conservation biology(Wiley, 2003-10-01)Area‐selection methods have recently gained prominence in conservation biology. A typical problem is to identify the minimum number of areas required to represent all species over some geographic region. Iterative heuristic methods have been developed by conservation scientists to solve these problems, although the solutions cannot be guaranteed to be optimal. Although optimal solutions can often be found, heuristics continue to be popular as they are perceived to be faster and more transparent as they are intuitively easy to understand. We used distributional data for 1921 bird species, 939 mammal species, 405 snake species, and 617 amphibian species compiled at the Zoological Museum, Univ. of Copenhagen for all 1° cells of mainland sub‐Saharan Africa to compare the quality of the solutions found using two heuristic methods (simple‐greedy algorithm and a progressive‐rarity algorithm) with optimal solutions. We found that the heuristic methods considered here often provide solutions as good as optimal solutions. Even in those cases where the optimal solutions were better the difference was relatively small, with the heuristics providing solutions requiring a 2–10% increase in area selected compared with the optimal solution, which importantly, represented an increase of <1% of the total area. Our study also suggests that the heuristic algorithms performed least well for datasets with few single cell endemics and taxa that tend to have larger range sizes. Despite the good quality of solutions using heuristics there was no time penalty associated with finding optimal solutions for the problems considered here, suggesting that the major obstacle to their use is making optimal methods accessible to conservation biologists. We encourage conservation biologists to work with operations researchers and so gain the benefit of their expertise and experience in solving these kinds of problems.
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ItemPerformance of sub-Saharan vertebrates as indicator groups for identifying priority areas for conservation(Wiley, 2003-02-01)Abstract: The aim of continental and global identification of priority areas for conservation is to identify particularly valuable areas for conservation on which to focus more‐detailed effort. Often, these sets of important areas, referred to as priority sets, have been identified through use of data on a single taxon (e.g., birds), which is assumed to act as an indicator for all biodiversity. Using a database of the distributions of 3882 vertebrate species in sub‐Saharan Africa, we conducted one of very few large‐scale tests of this assumption. We used six potential indicator groups—birds, mammals, amphibians, snakes, threatened birds, and threatened mammals—to find priority sets of 200 areas that best represent the species in that group. Priority sets of grid cells designed to maximize representation of a single indicator group captured 83–93% of species in the other groups. This high degree of representation is consistent with observed high levels of overlap in the patterns of distribution of species in different groups. Those species of highest conservation interest were more poorly represented, however, with only 75–88% of other groups' threatened species and 63–76% of other groups' narrow‐range species represented in the priority sets. We conclude that existing priority sets based on indicator groups provide a pragmatic basis for the immediate assessment of priorities for conservation at a continental scale. However, complete and efficient representation—especially of narrow‐range species—will not be achieved through indicator groups alone. Therefore, priority‐setting procedures must remain flexible so that new areas important for other taxa can be incorporated as data become available.
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ItemIntegrating costs into conservation planning across Africa(Elsevier BV, 2004-05-01)
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ItemThe history of allelopathy(Springer, 2007)
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ItemIn threat of co-extinction: two new species of Acizzia Heslop-Harrison (Hemiptera: Psyllidae) from vulnerable species of Acacia and Pultenaea(MAGNOLIA PRESS, 2009-10-07)Two new species of Acizzia, A. veski, sp. nov. and A. keithi, sp. nov. are described from the vulnerable or threatened plant species respectively, Acacia veronica Maslin (Fabaceae: Mimosoideae), with a restricted distribution in the southwest of Western Australia and Pultenaea glabra Benth. (Fabaceae: Faboideae), with a restricted distribution in eastern Australia. Pultenaea is recorded here as a new host genus record for Acizzia. Both new species of Acizzia are considered at risk of extinction as they have been recorded only from single localities on vulnerable or threatened hosts with restricted distributions.