bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparing foraging behaviour of small and large honey‐bee colonies by decoding waggle dances made by foragers
Authors: BEEKMAN M. , SUMPTER D. J. T. , SERAPHIDES N. , RATNIEKS F. L. W. 
Published: December 2004

Summary

We compared the foraging behaviour of two small (approximately 6000 bees) and two large (approximately 20 000 bees) honey‐bee colonies over 6 days. We determined where the bees of each colony foraged, whether they collected nectar or pollen, the number of patches foraged at, the number of bees engaged in foraging, and the concentration of the nectar collected.
Even though the colonies were located in the same environment and had the same genetic background, foragers from different colonies used different forage patches.
Small and large colonies foraged at a similar distance in July when forage was abundant (mean foraging distance for small and large colonies was 0·67 and 0·62 km, respectively) whereas the large colonies foraged significantly further in August when forage was scarce (mean foraging distance for small and large colonies was 1·43 and 2·85 km, respectively).
Small colonies foraged at approximately the same number of patches as large colonies. The total number of foragers returning to the small colonies per minute was significantly lower than the number of foragers returning to the large colonies. This means that, relative to their size, small colonies foraged at more patches than large colonies.
The quality of the nectar collected by foragers of the small and large colonies did not differ. However, small colonies did collect more pollen than large colonies.
Long‐term canopy dynamics in a large area of temperate old‐growth beech (Fagus crenata) forest: analysis by aerial photographs and digital elevation models
Authors: HENBO YUKO , ITAYA AKEMI , NISHIMURA NAOYUKI , YAMAMOTO SHIN‐ICHI 
Published: December 2004

Summary

Long‐term canopy dynamics in a large area of temperate old‐growth beech forest in the Daisen Forest Reserve, south‐western Japan (11.56 ha studied over 43 years), were investigated using digital elevation models (DEMs) of the canopy surface, constructed from aerial photographs taken in the growing season (i.e. with foliage) in 1958, 1978, 1992 and 2001. A ground surface DEM at the same resolution (a 2.5 × 2.5 m grid) was constructed using aerial photographs taken when foliage was absent (winter 2002). Canopy height data were obtained by calculating differences in elevation between the canopy and the ground surface, and a canopy height profile was constructed.
Topographic data for a 4‐ha plot, located within the 11.56‐ha area, were obtained via a ground survey and used to validate the ground surface DEM derived from aerial photographs.
Canopy height class distributions changed significantly over the 43 years. The total number of gaps, defined as areas where canopy height was ≤ 15 m, decreased but total gap area increased over time. Total gap area in 2001 was twice that of 1958. The density of gaps decreased as gap size increased.
Gap formation rates increased from 0.47% year−1 (1958–78) to 1.30% year−1 (1992–2001), with a mean of 0.77% year−1, and substantially exceeded closure rates, which fluctuated from 0.28% year−1 (1958–78) to 0.54% year−1 (1978–92), with a mean of 0.39% year−1. Gaps generally expanded and became connected to each other.
Temporal variation in gap formation and closure might be correlated with the frequency and severity of typhoon disturbances but, if the observed trends continue, this old‐growth beech stand may become an open stand. The long‐term dynamics of this forest type appear to be far from equilibrium.
Novel phenotypes among early generation hybrids of two Louisiana iris species: flooding experiments
Authors: JOHNSTON JILL A. , DONOVAN LISA A. , ARNOLD MICHAEL L. 
Published: December 2004

SummaryRecent studies of hybridization have shown that extreme (e.g. transgressive) phenotypes can be generated during massive genetic recombination events such as interspecific hybridization. Extreme hybrid phenotypes appear to have the potential to create new lineages and lead to evolutionary divergence.Hybrid genotypes of some salt marsh species have proven capable of reengineering their ecosystems, while in other cases, hybridization has transformed plant communities by facilitating species invasion.Using the Louisiana irises, a naturally hybridizing group of species, we assessed the potential for hybrids ofIris brevicaulisandI. fulvato possess extreme physiological and growth traits. Our glasshouse experiment used two soil water environments (wet and flood) to measure hybrid trait expression at both the genotypic class and individual genotype level.At the genotypic class level, two of the three hybrid classes (F1s, and backcrosses towards each parental species) were transgressive for at least one physiological trait (F1s for root mass proportion, specific leaf area and final leaf area; backcrosses toI. brevicaulisfor leaf area ratio). Three fitness components (total biomass, ramet production and flower production) were measured on each plant in the experiment. All three hybrid classes had greater clonal fitness (total biomass) but not greater sexual fitness (flower number) than parent species.At the individual genotype level, two F1hybrids showed extreme physiological trait expression: one for specific leaf area, and the other for shallow root allocation. Flower production was the only fitness component that showed some degree of environment‐dependence at the individual genotype level.Although early generation hybrid classes can contain rare genotypes with extreme phenotypic trait expression, and hybrid fitness components were equal or superior to both parental species in most cases, there was not a strong association between transgressive traits and elevated hybrid fitness.
Factors predisposing episodic drought‐induced tree mortality in Nothofagus– site, climatic sensitivity and growth trends
Authors: SUAREZ MARIA LAURA , GHERMANDI LUCIANA , KITZBERGER THOMAS 
Published: December 2004

Summary

Although climatic variability is a strong driving force for forest dynamics, drought‐induced mortality has generally received much less attention than other types of disturbance.
In 1998–99 northern Patagonia was affected by one of the most severe droughts of the 20th century, coinciding with a strong La Nina event, and this caused high mortality of Nothofagus dombeyi (coihue), the dominant tree species in Nahuel Huapi National Park.
Factors involved in determining this mortality of N. dombeyi were examined at both patch and tree level. Radial growth characteristics of killed trees and survivors were compared by dendrochronological analyses. Relationships between growth and climate were investigated using response function analysis.
At the tree scale, individuals with variable growth were more prone to die from drought than trees with more regular growth. Juveniles whose growth patterns showed sensitivity to climate were particularly likely to die. However, among both killed trees and survivors, older trees were less sensitive to climate.
Mean growth rate was a good predictor of mortality in adult trees, showing that trees with slower growth rate were more susceptible to drought. Susceptible trees may have been negatively affected by the drought that affected northern Patagonia in 1956–57.
These results underscore the importance of considering drought‐induced tree mortality as a non‐random mechanism influenced by site, previous stress/disturbance history, ontogeny, vigour, climatic sensitivity and physiology. Spatial patterns of extensive full and partial crown dieback, which are evident in many temperate forests worldwide, may reflect the superposition of these predisposing factors on strong/repeated interannual fluctuations of climate.
Anaerobicity Prepares
Saccharomyces cerevisiae
Cells for Faster Adaptation to Osmotic Shock
Authors: Krantz Marcus , Nordlander Bodil , Valadi Hadi , Johansson Mikael , Gustafsson Lena , Hohmann Stefan 
Published: December 2004

ABSTRACT

Yeast cells adapt to hyperosmotic shock by accumulating glycerol and altering expression of hundreds of genes. This transcriptional response of
Saccharomyces cerevisiae
to osmotic shock encompasses genes whose products are implicated in protection from oxidative damage. We addressed the question of whether osmotic shock caused oxidative stress. Osmotic shock did not result in the generation of detectable levels of reactive oxygen species (ROS). To preclude any generation of ROS, osmotic shock treatments were performed in anaerobic cultures. Global gene expression response profiles were compared by employing a novel two-dimensional cluster analysis. The transcriptional profiles following osmotic shock under anaerobic and aerobic conditions were qualitatively very similar. In particular, it appeared that expression of the oxidative stress genes was stimulated upon osmotic shock even if there was no apparent need for their function. Interestingly, cells adapted to osmotic shock much more rapidly under anaerobiosis, and the signaling as well as the transcriptional response was clearly attenuated under these conditions. This more rapid adaptation is due to an enhanced glycerol production capacity in anaerobic cells, which is caused by the need for glycerol production in redox balancing. Artificially enhanced glycerol production led to an attenuated response even under aerobic conditions. These observations demonstrate the crucial role of glycerol accumulation and turgor recovery in determining the period of osmotic shock-induced signaling and the profile of cellular adaptation to osmotic shock.
Potential Link between the NIMA Mitotic Kinase and Nuclear Membrane Fission during Mitotic Exit inAspergillus nidulans
Authors: Davies Jonathan R. , Osmani Aysha H. , De Souza Colin P. C. , Bachewich Catherine , Osmani Stephen A. 
Published: December 2004

ABSTRACTWe have isolated TINC as a NIMA-interacting protein by using the yeast two-hybrid system and have confirmed that TINC interacts with NIMA inAspergillus nidulans. The TINC-NIMA interaction is stabilized in the absence of phosphatase inhibitors and in the presence of kinase-inactive NIMA, suggesting that the interaction is enhanced when NIMA is not fully activated. TINC is a cytoplasmic protein. TINC homologues and a TINC-like protein (A. nidulansHETC) are conserved in other filamentous fungi. Neither deletion oftinCnor deletion of bothtinCandA. nidulans hetCis lethal, but deletion oftinCdoes produce cold sensitivity as well as osmotic sensitivity. Expression of an amino-terminal-truncated form of TINC (ΔN-TINC) inhibits colony growth inAspergillusand localizes to membrane-like structures within the cell. Examination of cell cycle progression in these cells reveals that they progress through multiple defective mitoses. Many cells contain large polyploid single nuclei, while some appear to have separated masses of DNA. Examination of the nuclear envelopes of cells containing more than one DNA mass reveals that both DNA masses are contained within a single nuclear envelope, indicating that nuclear membrane fission is defective. The ability of these cells to separate DNA segregation from nuclear membrane fission suggests that this coordination is normally a regulated process inA. nidulans. Additional experiments demonstrate that expression of ΔN-TINC results in premature NIMA disappearance in mitotic samples. We propose that TINC's interaction with NIMA and the cell cycle defects produced by ΔN-TINC expression suggest possible roles for TINC and NIMA during nuclear membrane fission.
Selection and Characterization of RNA Interference-Deficient Trypanosomes Impaired in Target mRNA Degradation
Authors: Shi Huafang , Chamond Nathalie , Tschudi Christian , Ullu Elisabetta 
Published: December 2004

ABSTRACT

Genetic analysis of the RNA interference (RNAi) pathway in
Trypanosoma brucei
has so far revealed one essential component, namely,
TbAGO1
, encoding a member of the Argonaute protein family. To gain further insight into the RNAi mechanism and its biological significance, we selected RNAi-deficient trypanosomes by using repeated cycles of electroporation with α-tubulin double-stranded RNA, a treatment that blocks cytokinesis in wild-type cells. Two independent clones, termed RiD-1 (for RNAi-deficient clone 1) and RiD-2, were characterized. At the cellular level, only RiD-1 trypanosomes showed a significant increase in doubling time with the concomitant accumulation of cells defective in the completion of cytokinesis. At the RNA level, both clones accumulated wild-type amounts of small interfering RNAs and displayed elevated levels of retroposon transcripts, the hallmark of RNAi deficiency in
T. brucei
. Importantly, both RiD-1 and RiD-2 clones were defective in the degradation of target mRNA, suggesting an impairment of the activity of AGO1, the putative RNAi endonuclease. Since in RiD cells the
AGO1
gene was not mutated and was expressed at wild-type levels, we propose that in trypanosomes the cleavage of mRNA by AGO1 is regulated by the interaction with another factor(s).
Morphogenetic Pathway of Spore Wall Assembly in
Saccharomyces cerevisiae
Authors: Coluccio Alison , Bogengruber Edith , Conrad Michael N. , Dresser Michael E. , Briza Peter , Neiman Aaron M. 
Published: December 2004

ABSTRACT

The
Saccharomyces cerevisiae
spore is protected from environmental damage by a multilaminar extracellular matrix, the spore wall, which is assembled de novo during spore formation. A set of mutants defective in spore wall assembly were identified in a screen for mutations causing sensitivity of spores to ether vapor. The spore wall defects in 10 of these mutants have been characterized in a variety of cytological and biochemical assays. Many of the individual mutants are defective in the assembly of specific layers within the spore wall, leading to arrests at discrete stages of assembly. The localization of several of these gene products has been determined and distinguishes between proteins that likely are involved directly in spore wall assembly and probable regulatory proteins. The results demonstrate that spore wall construction involves a series of dependent steps and provide the outline of a morphogenetic pathway for assembly of a complex extracellular structure.
Saccharomyces cerevisiae
Aqr1 Is an Internal-Membrane Transporter Involved in Excretion of Amino Acids
Authors: Velasco Isabel , Tenreiro Sandra , Calderon Isabel L. , André Bruno 
Published: December 2004

ABSTRACT

Excretion of amino acids by yeast cells was reported long ago but has not been characterized in molecular terms. It is typically favored by overproduction of the amino acid and/or impairment of its uptake. Here we describe the construction of a yeast strain excreting threonine and homoserine. Using this excretor strain, we then applied a reverse-genetics approach and found that the transporter encoded by the
YNL065w/AQR1
gene, a protein thought to mediate H
+
antiport, is involved in homoserine and threonine excretion. Furthermore, overexpression of
AQR1
led to increased excretion of several amino acids (alanine, aspartate, and glutamate) known to be relatively abundant in the cytosol. Transcription of the
AQR1
gene is induced severalfold by a number of amino acids and appears to be under the negative control of Gcn4. An Aqr1-green fluorescent protein fusion protein is located in multiple internal membrane structures and appears to cycle continuously between these compartments and the plasma membrane. The Aqr1 sequence is significantly similar to the vesicular amine transporters of secretory vesicles of neuronal cells. We propose that Aqr1 catalyzes transport of excess amino acids into vesicles, which then release them in the extracellular space by exocytosis.
Cas3p Belongs to a Seven-Member Family of Capsule Structure Designer Proteins
Authors: Moyrand Frédérique , Chang Yun C. , Himmelreich Uwe , Kwon-Chung Kyung J. , Janbon Guilhem 
Published: December 2004

ABSTRACT

The polysaccharide capsule is the main virulence factor of the basidiomycetous yeast
Cryptococcus neoformans
. Four genes (
CAP10
,
CAP59
,
CAP60
, and
CAP64
) essential for capsule formation have been previously identified, although their roles in the biosynthetic pathway remain unclear. A genetic and bioinformatics approach allowed the identification of six
CAP64
-homologous genes, named
CAS3
,
CAS31
,
CAS32
,
CAS33
,
CAS34
, and
CAS35
, in the
C. neoformans
genome. This gene family is apparently specific in a subclass of the basidiomycete fungi. Single as well as double deletions of these genes in all possible combinations demonstrated that none of the
CAP64
-homologous genes were essential for capsule formation, although the
cas35Δ
strains displayed a hypocapsular phenotype. The chemical structure of the glucuronomannan (GXM) produced by the
CAS
family deletants revealed that these genes determined the position and the linkage of the xylose and/or
O
-acetyl residues on the mannose backbone. Hence, these genes are all involved in assembly of the GXM structure in
C. neoformans
.
Cellular Localization and Role of Kinase Activity of
PMK1
in
Magnaporthe grisea
Authors: Bruno Kenneth S. , Tenjo Fernando , Li Lei , Hamer John E. , Xu Jin-Rong 
Published: December 2004

ABSTRACT

A mitogen-activated protein (MAP) kinase gene,
PMK1
, is known to regulate appressorium formation and infectious hyphal growth in the rice blast fungus
Magnaporthe grisea
. In this study, we constructed a green fluorescent protein gene-
PMK1
fusion (GFP-
PMK1
) to examine the expression and localization of
PMK1
in
M. grisea
during infection-related morphogenesis. The GFP
-PMK1
fusion encoded a functional protein that complemented the defect of the
pmk1
deletion mutant in appressorium formation and plant infection. Although a weak GFP signal was detectable in vegetative hyphae, conidia, and germ tubes, the expression of GFP-Pmk1 was increased in appressoria and developing conidia. Nuclear localization of GFP-Pmk1 proteins was observed in a certain percentage of appressoria. A kinase-inactive allele and a nonphosphorylatable allele of
PMK1
were constructed by site-directed mutagenesis. Expression of these mutant
PMK1
alleles did not complement the
pmk1
deletion mutant. These data confirm that kinase activity and activation of
PMK1
by the upstream MAP kinase kinase are required for appressorium formation and plant infection in
M. grisea
. When overexpressed with the RP27 promoter in the wild-type strain, both the kinase-inactive and nonphosphorylatable
PMK1
fusion proteins caused abnormal germ tube branching. Overexpression of these
PMK1
mutant alleles may interfere with the function of native
PMK1
during appressorium formation.
The Histone Fold Domain of Cse4 Is Sufficient for
CEN
Targeting and Propagation of Active Centromeres in Budding Yeast
Authors: Morey Lisa , Barnes Kelly , Chen Yinhuai , Fitzgerald-Hayes Molly , Baker Richard E. 
Published: December 2004

ABSTRACT

Centromere-specific H3-like proteins (CenH3s) are conserved across the eukaryotic kingdom and are required for packaging centromere DNA into a specialized chromatin structure required for kinetochore assembly. Cse4 is the CenH3 protein of the budding yeast
Saccharomyces cerevisiae
. Like all CenH3 proteins, Cse4 consists of a conserved histone fold domain (HFD) and a divergent N terminus (NT). The Cse4 NT contains an essential domain designated END (for essential N-terminal domain); deletion of END is lethal. To investigate the role of the Cse4 NT in centromere targeting, a series of deletion alleles (
cse4
Δ
NT
) were analyzed. No part of the Cse4 NT was required to target mutant proteins to centromere DNA in the presence of functional Cse4. A Cse4 degron strain was used to examine targeting of a Cse4ΔNT protein in the absence of wild-type Cse4. The END was not required for centromere targeting under these conditions, confirming that the HFD confers specificity of Cse4 centromere targeting. Surprisingly, overexpression of the HFD bypassed the requirement for the END altogether, and viable
S. cerevisiae
strains in which the cells express only the Cse4 HFD and six adjacent N-terminal amino acids (Cse4Δ129) were constructed. Despite the complete absence of the NT, mitotic chromosome loss in the
cse4
Δ
129
strain increased only 6-fold compared to a 15-fold increase in strains overexpressing wild-type Cse4. Thus, when overexpressed, the Cse4 HFD is sufficient for centromere function in
S. cerevisiae
, and no posttranslational modification or interaction of the NT with other kinetochore component(s) is essential for accurate chromosome segregation in budding yeast.
G-Protein β Subunit of
Cochliobolus heterostrophus
Involved in Virulence, Asexual and Sexual Reproductive Ability, and Morphogenesis
Authors: Ganem Sherif , Lu Shun-Wen , Lee Bee-Na , Chou David Yu-Te , Hadar Ruthi , Turgeon B. Gillian , Horwitz Benjamin A. 
Published: December 2004

ABSTRACT

Previous work established that mutations in mitogen-activated protein (MAP) kinase (
CHK1
) and heterotrimeric G-protein α (Gα) subunit (
CGA1
) genes affect the development of several stages of the life cycle of the maize pathogen
Cochliobolus heterostrophus
. The effects of mutating a third signal transduction pathway gene,
CGB1
, encoding the Gβ subunit, are reported here.
CGB1
is the sole Gβ subunit-encoding gene in the genome of this organism.
cgb1
mutants are nearly wild type in vegetative growth rate; however, Cgb1 is required for appressorium formation, female fertility, conidiation, regulation of hyphal pigmentation, and wild-type virulence on maize. Young hyphae of
cgb1
mutants grow in a straight path, in contrast to those of the wild type, which grow in a wavy pattern. Some of the phenotypes conferred by mutations in
CGA1
are found in
cgb1
mutants, suggesting that Cgb1 functions in a heterotrimeric G protein; however, there are also differences. In contrast to the deletion of
CGA1
, the loss of
CGB1
is not lethal for ascospores, evidence that there is a Gβ subunit-independent signaling role for Cga1 in mating. Furthermore, not all of the phenotypes conferred by mutations in the MAP kinase
CHK1
gene are found in
cgb1
mutants, implying that the Gβ heterodimer is not the only conduit for signals to the MAP kinase
CHK1
module. The additional phenotypes of
cgb1
mutants, including severe loss of virulence on maize and of the ability to produce conidia, are consistent with
CGB1
being unique in the genome. Fluorescent DNA staining showed that there is often nuclear degradation in mature hyphae of
cgb1
mutants, while comparable wild-type cells have intact nuclei. These data may be genetic evidence for a novel cell death-related function of the Gβ subunit in filamentous fungi.