bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gγ1 + Gγ2 ≠ Gβ: Heterotrimeric G Protein Gγ-Deficient Mutants Do Not Recapitulate All Phenotypes of Gβ-Deficient Mutants
Authors: Trusov Yuri , Zhang Wei , Assmann Sarah M. , Botella José Ramón 
Published: April 2008

AbstractHeterotrimeric G proteins are signaling molecules ubiquitous among all eukaryotes. The Arabidopsis (Arabidopsis thaliana) genome contains one Gα (GPA1), one Gβ (AGB1), and two Gγ subunit (AGG1 and AGG2) genes. The Gβ requirement of a functional Gγ subunit for active signaling predicts that a mutant lacking both AGG1 and AGG2 proteins should phenotypically resemble mutants lacking AGB1 in all respects. We previously reported that Gβ- and Gγ-deficient mutants coincide during plant pathogen interaction, lateral root development, gravitropic response, and some aspects of seed germination. Here, we report a number of phenotypic discrepancies between Gβ- and Gγ-deficient mutants, including the double mutant lacking both Gγ subunits. While Gβ-deficient mutants are hypersensitive to abscisic acid inhibition of seed germination and are hyposensitive to abscisic acid inhibition of stomatal opening and guard cell inward K+ currents, none of the available Gγ-deficient mutants shows any deviation from the wild type in these responses, nor do they show the hypocotyl elongation and hook development defects that are characteristic of Gβ-deficient mutants. In addition, striking discrepancies were observed in the aerial organs of Gβ- versus Gγ-deficient mutants. In fact, none of the distinctive traits observed in Gβ-deficient mutants (such as reduced size of cotyledons, leaves, flowers, and siliques) is present in any of the Gγ single and double mutants. Despite the considerable amount of phenotypic overlap between Gβ- and Gγ-deficient mutants, confirming the tight relationship between Gβ and Gγ subunits in plants, considering the significant differences reported here, we hypothesize the existence of new and as yet unknown elements in the heterotrimeric G protein signaling complex.
The Wheat Mitogen-Activated Protein Kinases TaMPK3 and TaMPK6 Are Differentially Regulated at Multiple Levels during Compatible Disease Interactions withMycosphaerella graminicola
Authors: Rudd Jason J. , Keon John , Hammond-Kosack Kim E. 
Published: April 2008

AbstractMany race- or isolate-specific disease resistance responses of plants toward pathogens (incompatible interactions) invoke hypersensitive response (HR)-like programmed cell death (PCD) and the coordinated activation of mitogen-activated protein kinases homologous with Arabidopsis (Arabidopsis thaliana) AtMPK6 and AtMPK3 (or tobacco [Nicotiana tabacum] SIPK and WIPK), respectively. Resistance of wheat (Triticum aestivum) leaves to the necrotrophic fungal pathogen Mycosphaerella graminicola can also operate at an isolate/cultivar-specific level. We confirm here that resistance is achieved without any sign of HR-like PCD during the incompatible interaction. Instead, PCD is strictly associated with the compatible interaction and is triggered during disease symptom expression. A strong transcriptional activation of TaMPK3, the wheat homolog of Arabidopsis AtMPK3, was observed immediately preceding PCD and symptom development in the compatible interaction. Generation and use of TaMPK3- and TaMPK6-specific antibodies on western blots and in coupled immunoprecipitation-protein kinase assays demonstrated that the TaMPK3 protein also accumulated, and was subsequently posttranslationally activated, during the compatible interaction in parallel to PCD. In contrast, no increase in expression, protein levels, or posttranslational activation of TaMPK6 was observed at any stage of either compatible or incompatible interactions. However, the protein levels of TaMPK6 became markedly reduced during the compatible interaction coincident with the onset of TaMPK3 protein accumulation. These data highlight the emerging similarity between the signaling pathways triggered in a host plant during successful infection by a necrotrophic fungal pathogen and the resistance responses normally effective against biotrophs.
A Pentapeptide Motif Related to a Pigment Binding Site in the Major Light-Harvesting Protein of Photosystem II, LHCII, Governs Substrate-Dependent Plastid Import of NADPH:Protochlorophyllide Oxidoreductase A
Authors: Reinbothe Christiane , Pollmann Stephan , Phetsarath-Faure Phetaphine , Quigley Françoise , Weisbeek Peter , Reinbothe Steffen 
Published: April 2008

Abstract
NADPH:protochlorophyllide (Pchlide) oxidoreductase (POR) A is the only known example thus far of a nucleus-encoded plastid protein that is imported to its final destination in a substrate-dependent, Pchlide-regulated manner. Previous work has shown that the cytosolic PORA precursor (pPORA) does not utilize the general import site but uses a distinct translocon designated the Pchlide-dependent translocon complex. Here we demonstrate that a pentapeptide motif, threonine-threonine-serine-proline-glycine (TTSPG) in pPORA's transit peptide (transA), is involved in Pchlide-dependent transport. Deletion of this motif from the COOH-terminal end of transA abolished both Pchlide binding and protein import. Incorporation of the TTSPG motif into normally non-Pchlide-responsive transit sequences conferred the pigment binding properties onto the engineered chimeric precursors but was insufficient to render protein import substrate dependent. An additional motif was identified in the NH2-terminal part of transA that was needed for binding of the precursor to the Pchlide-dependent translocon complex. Point mutations of the TTSPG motif identified glycine as the Pchlide binding site. By analogy to the major light-harvesting chlorophyll a/b binding protein of photosystem II, we propose that the peptidyl carbonyl oxygen of glycine may bind directly or via a water molecule to the central Mg atom of the pigment.
Plastid Transcriptomics and Translatomics of Tomato Fruit Development and Chloroplast-to-Chromoplast Differentiation: Chromoplast Gene Expression Largely Serves the Production of a Single Protein
Authors: Kahlau Sabine , Bock Ralph 
Published: April 2008

AbstractPlastid genes are expressed at high levels in photosynthetically active chloroplasts but are generally believed to be drastically downregulated in nongreen plastids. The genome-wide changes in the expression patterns of plastid genes during the development of nongreen plastid types as well as the contributions of transcriptional versus translational regulation are largely unknown. We report here a systematic transcriptomics and translatomics analysis of the tomato (Solanum lycopersicum) plastid genome during fruit development and chloroplast-to-chromoplast conversion. At the level of RNA accumulation, most but not all plastid genes are strongly downregulated in fruits compared with leaves. By contrast, chloroplast-to-chromoplast differentiation during fruit ripening is surprisingly not accompanied by large changes in plastid RNA accumulation. However, most plastid genes are translationally downregulated during chromoplast development. Both transcriptional and translational downregulation are more pronounced for photosynthesis-related genes than for genes involved in gene expression, indicating that some low-level plastid gene expression must be sustained in chromoplasts. High-level expression during chromoplast development identifies accD, the only plastid-encoded gene involved in fatty acid biosynthesis, as the target gene for which gene expression activity in chromoplasts is maintained. In addition, we have determined the developmental patterns of plastid RNA polymerase activities, intron splicing, and RNA editing and report specific developmental changes in the splicing and editing patterns of plastid transcripts.
Analysis of theArabidopsisHistidine Kinase ATHK1 Reveals a Connection between Vegetative Osmotic Stress Sensing and Seed Maturation
Authors: Wohlbach Dana J. , Quirino Betania F. , Sussman Michael R. 
Published: April 2008

AbstractTo cope with water stress, plants must be able to effectively sense, respond to, and adapt to changes in water availability. The Arabidopsis thaliana plasma membrane His kinase ATHK1 has been suggested to act as an osmosensor that detects water stress and initiates downstream responses. Here, we provide direct genetic evidence that ATHK1 not only is involved in the water stress response during early vegetative stages of plant growth but also plays a unique role in the regulation of desiccation processes during seed formation. To more comprehensively identify genes involved in the downstream pathways affected by the ATHK1-mediated response to water stress, we created a large-scale summary of expression data, termed the AtMegaCluster. In the AtMegaCluster, hierarchical clustering techniques were used to compare whole-genome expression levels in athk1 mutants with the expression levels reported in publicly available data sets of Arabidopsis tissues grown under a wide variety of conditions. These experiments revealed that ATHK1 is cotranscriptionally regulated with several Arabidopsis response regulators, together with two proteins containing novel sequences. Since overexpression of ATHK1 results in increased water stress tolerance, our observations suggest a new top-down route to increasing drought resistance via receptor-mediated increases in sensing water status, rather than through genetically engineered changes in downstream transcription factors or specific osmolytes.
Reduced V-ATPase Activity in thetrans-Golgi Network Causes Oxylipin-Dependent Hypocotyl Growth Inhibition inArabidopsis
Authors: Brüx Angela , Liu Tzu-Yin , Krebs Melanie , Stierhof York-Dieter , Lohmann Jan U. , Miersch Otto , Wasternack Claus , Schumacher Karin 
Published: April 2008

AbstractRegulated cell expansion allows plants to adapt their morphogenesis to prevailing environmental conditions. Cell expansion is driven by turgor pressure created by osmotic water uptake and is restricted by the extensibility of the cell wall, which in turn is regulated by the synthesis, incorporation, and cross-linking of new cell wall components. The vacuolar H+-ATPase (V-ATPase) could provide a way to coordinately regulate turgor pressure and cell wall synthesis, as it energizes the secondary active transport of solutes across the tonoplast and also has an important function in the trans-Golgi network (TGN), which affects synthesis and trafficking of cell wall components. We have previously shown that det3, a mutant with reduced V-ATPase activity, has a severe defect in cell expansion. However, it was not clear if this is caused by a defect in turgor pressure or in cell wall synthesis. Here, we show that inhibition of the tonoplast-localized V-ATPase subunit isoform VHA-a3 does not impair cell expansion. By contrast, inhibition of the TGN-localized isoform VHA-a1 is sufficient to restrict cell expansion. Furthermore, we provide evidence that the reduced hypocotyl cell expansion in det3 is conditional and due to active, hormone-mediated growth inhibition caused by a cell wall defect.
Combinatorial engineering to enhance thermostability of amylosucrase
Authors: Emond Stéphane , André Isabelle , Jaziri Kais , Potocki‐Véronèse Gabrielle , Mondon Philippe , Bouayadi Khalil , Kharrat Hakim , Monsan Pierre , Remaud‐Simeon Magali 
Published: April 2008

AbstractAmylosucrase is a transglucosidase that catalyzes amylose‐like polymer synthesis from sucrose substrate. About 60,000 amylosucrase variants from two libraries generated by the MutaGen random mutagenesis method were submitted to an in vivo selection procedure leading to the isolation of more than 7000 active variants. These clones were then screened for increased thermostability using an automated screening process. This experiment yielded three improved variants (two double mutants and one single mutant) showing 3.5‐ to 10‐fold increased half‐lives at 50°C compared to the wild‐type enzyme. Structural analysis revealed that the main differences between wild‐type amylosucrase and the most improved variant (R20C/A451T) might reside in the reorganization of salt bridges involving the surface residue R20 and the introduction of a hydrogen‐bonding interaction between T451 of the B′ domain and D488 of flexible loop 8. This double mutant is the most thermostable amylosucrase known to date and the only one usable at 50°C. At this temperature, amylose synthesis by this variant using high sucrose concentration (600 mM) led to the production of amylose chains twice as long as those obtained by the wild‐type enzyme at 30°C.
THE BLACK RHINOCEROS (DICEROS BICORNIS L.)
Authors: Ritchie A. T. A. 
Published: April 2008

SummaryThe two African genera of rhinoceroses are briefly compared and an account given of the distribution of the black rhinoceros (Diceros bicornis L.). This species, which is adapted to a wide range of habitats, is now absent from or scarce in many parts of Africa where it was common only 50 or 100 years ago. It is described in detail with comments on the validity of the two subspecies D. b. bicornis and D. b. somaliensis Potocki.Daily activity and home range of the black rhinoceroy are largely related to its water requirements. and it normally drinks once in 24 hours. In order to feed it may move 5–15 miles from the watering place along regular paths; feeding takes place in the early morning and evening and the remainder of the day is spent resting in shaue. A constant behaviour pattern during defaecation and urination is described.A group or herd is usually composed of one, two or three individuals. Mating may take place at any time during the year. The disposition of individual animals is considered to be related to the degree to which they have been persecuted by man; in different areas, inhabited by hunting or pastoral tribes, a marked difference in behaviour is apparent. Instances have been recorded of black rhinoceroses being killed by elephants (Loxodonta africana Blumenbach) and by lions (Panther a leo Linnaeus).An account is given of the structure of the horns and the way in which they are used. and of their commercial value. Poaching of the species in Kenya is carried out largely by means of poisoned arrows or leg snares.Warning is given of the urgent need for strict measures to concerve the species. which will only survive in sanctuaries where its interests are paramount. Its decline is due not only to the impact of man but to its apparent inability to extend its range into areas where rhinos have not formerly existed. It is one of the species in most danger of extinction.(Editorial note: this paper was written by the late A. T. A. Ritchie, Chief Game Warden of Kenya from 1923 to 1948, some time before his death in 1962. Ritchie was a fine observer and naturalist whose special interest was the black rhinoceros, and the editorial committee consider it particularly suitable that this record of his observations should be published in the first number of the East African Wildlife Journal to which he would undoubtedly have given wholehearted support. It should be pointed out that certain facts in the paper are now outdated. Some authorities consider the white rhino to be a species of Diceros, and poaching and other effects of man's presence are now a major factor in the decline of the black rhinoceros. Even with the present degree of control poaching is rife, and if this control is materially decreased the rhinoceros will undoubtedly rapidly disappear from many areas.)
OBSERVATIONS ON THE GREATER KUDU TRAGELAPHUS STREPSICEROS PALLAS FROM A TSETSE CONTROL HUNTING SCHEME IN NORTHERN RHODESIA
Authors: Wilson Vivian J. 
Published: April 2008

SummaryMaterial from kudu shot on tsetse control was studied for information on breeding and feeding habits. A number of animals was measured and weighed, illustrating that males were bigger than females.Field observations and stomach contents showed that the species is mainly a browser eating a wide variety of plants.A marked peak of calving was observed and this coincided with the tall grass season (January‐April), when the newly‐born young are apparently hidden. Kudu in the area studied may be solitary but are generally associated in small groups of about four, although as many as eleven have been seen together in the study area.
A SURVEY OF PAST AND PRESENT WILDLIFE RESEARCH IN EAST AFRICA*
Authors: Talbot Lee M. 
Published: April 2008

SummaryThe survey involved visits throughout East Africa to contact those concerned with wildlife research, as well as a review of the available literature. This paper presents the results of the survey.Wildlife research in East Africa is not a unified field and pertinent data come from a variety of disciplines. Broadly speaking there are four major types of research involving wildlife that have been or are being carried out in East Africa:1. Observations on natural history;2. Taxonomic and distributional studies;3. Research in other fields which happens to involve wildlife;4. Systematic research focused on wildlife itself.To facilitate the use of this report the information on research projects and research workers has been presented under a series of subject headings, as follows: background and early references (p. 62), techniques (p. 63), taxonomy and nomenclature (p. 66), distribution and habitat preferences (p. 67), studies on individual species of large herbivores (p. 67), studies of predators (p. 69), ecological studies, including those of groups of associated animals (p. 69), population dynamics (p. 70), carrying capacity and biomass (p. 71), movements (p. 71), nutrition (p. 72), anatomy and physiology (p. 73), diseases and parasites (p. 73), small mammals (p. 75), birds (p. 75), reptiles (p. 75), primates (p. 76), vermin (p. 76), co‐ordination and publication of research (p. 76). Some studies of course appear under more than one heading. Within each heading the research is presented in chronological order. References, where available, are cited and the location of reports, files and sources of further information on each subject is noted.
THE USE OF GAME TRAILS AS A POSSIBLE MEASURE OF HABITAT UTILISATION BY LARGER MAMMALS
Authors: Agnew A.D.Q. 
Published: April 2008

SummaryPercentage cover of game trails is discussed as a possible measure of total habitat utilisation by larger mammals and a technique for its measurement is described. Game trail cover in Tsavo National Park (East) at Voi has been analysed in two areas, woodland and grassland. Of these the woodland had the higher trail cover (10.69%) and grassland the lower (7.57%). The interpretation of these results is discussed.
THE FEEDING HABITS OF THE YELLOW‐NECKED SPURFOWL (PTERNISTIS LEUCOSCEPU8) IN NORTHERN TANZANIA
Authors: Stronach B. 
Published: April 2008

SummaryIn late 1984 and throughout 1965 the feeding habits of Pternistis leucoscepus were studied in the north of Tanzania and in the Tsavo West National Park in Kenya.The main food of this bird was found to be the corms of the sedge Cyperus rotundus. Grass and legume seeds and insects formed a small proportion of the diet. P. leucoscepus is not dependent on free water and can occupy waterless country.The species' main habitat is the edge of flood plains with abundant C. rotundus sedge, bounded by shrub and small tree cover.In the two main study areas, Ngase‐rai and Tarangire, the difference in the general density of the habitats is reflected in the occurrence of P. leucoscepus and Francolinus sephaena together in the former area, and of P. leucoscepus, P. cranchii, F. sephaena and F. hildebrandti in the latter. The sympat‐ric occurrence of these related game birds and the apparent similarity of the two spurfowls' feeding habits presents a fascinating ecological problem for further study.
THE EFFECTS OF TSETSE CONTROL OPERATIONS ON COMMON DUIKER IN EASTERN ZAMBIA
Authors: Wilson V. J. , Roth H. H. 
Published: April 2008

SummaryThe effects of intensive Tsetse Control hunting operations on a duiker population (Sylvicapra grimmia) were investigated in a 200 sq. mile area in Eastern Zambia. Two years of hunting were insufficient to reduce this population so significantly that a marked shift of its age composition towards the juvenile age classes resulted. There were, however, indications of beginning accelerated population growth through increased breeding and inclusion of more juveniles in the reproduction process, as a first response to the hunting pressure. Although general availability of duiker did not diminish, they became increasingly difficult to shoot because of behavioural adaptation and changing periods of feeding activity. Neither hunting nor various other human disturbances provoked emigration from the area or a change of the seasonal pattern of localised movement.The studied hunting operation failed to remove more than the annual increment to the duiker population and in respect of this species was thus ineffective as a means of Tsetse Control.Implications of the results of this study for the management of duiker for sustained meat production are discussed.
NOTES ON SOME ANTS IN NORTHERN SOMALIA
Authors: Glover P. E. 
Published: April 2008

SummaryThe paper describes observations made over a period of two years on the feeding habits, general ecology and distribution of five species of ants (harvester‐, stink‐, soldier‐, tree‐, and sugar‐ants) in Northern Somalia, p‐incipally in the plains and bushland of the Haud.Harvester and stink ants are discussed in some detail, and some dimensions of excavated nests and runways are given. The occurrence of associated insects is noted and the ecological roles of seed‐eating and predatory ants (particularly in relation to termites) are discussed.There are notes on the climate and topography of the region, and a glossary of vernacular names is appended.
NAIROBI NATIONAL PARK GAME CENSUS, 1966
Authors: Foster J. B. , Kearney D. 
Published: April 2008

Summary1. The monthly game counts of Nairobi National Park in 1966 are compared with those of 1961 to 1983 inclusive. It appears that the mean an‐nual population of wild ungulates has remained constant at about 4000 animais after a severe decline during the drought of 1961.2. Wildebeest have continued to decline since the drought and there is no evidence of the former migration to the Athi‐Kapiti plains. Reasons for these phenomena are proposed.3. Kongoni have continued to in‐crease since their decline in 1961 and little migration to the plains could be detected in 1966.4. The mean yearly population of zebra has remained constant since their decline in 1961. At present this is the only species to migrate in large num‐bers to and from the plains with the onset and cessation of the rains.5. Other ungulates were less affected by the drought and their numbers in 1966 appear to have changed relatively little since the beginning of 1961.6. Females predomInate in the adult populations of all the common plains ungulates.7. In 1966 lions killed wildebeest at a rate four times greater than would be expected from the percentage of wildebeest in the population. Reasons for this are suggested. As the wildebeest have declined in numbers, the lion have included higher percentages of zebra, warthog, kongoni and eland in their diets.