Diet of chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda, 2. Temporal variation and fallback foods

Highly frugivorous primates like chimpanzees (Pan trogolodytes) must contend with temporal variation in food abundance and quality by tracking fruit crops and relying more on alternative foods, some of them fallbacks, when fruit is scarce. We used behavioral data from 122 months between 1995 and 2009 plus 12 years of phenology records to investigate temporal dietary variation and use of fallback foods by chimpanzees at Ngogo, Kibale National Park, Uganda. Fruit, including figs, comprised most of the diet. Fruit and fig availability varied seasonally, but the exact timing of fruit production and the amount of fruit produced varied extensively from year to year, both overall and within and among species. Feeding time devoted to all major fruit and fig species was positively associated with availability, reinforcing the argument that chimpanzees are ripe fruit specialists. Feeding time devoted to figs-particularly Ficus mucuso (the top food)--varied inversely with the abundance of nonfig fruits and with foraging effort devoted to such fruit. However, figs contributed much of the diet for most of the year and are best seen as staples available most of the time and eaten in proportion to availability. Leaves also contributed much of the diet and served as fallbacks when nonfig fruits were scarce. In contrast to the nearby Kanywara study site in Kibale, pith and stems contributed little of the diet and were not fallbacks. Fruit seasons (periods of at least 2 months when nonfig fruits account for at least 40% of feeding time; Gilby & Wrangham., Behavioral Ecology and Sociobiology 61:1771-1779, 2007) were more common at Ngogo than Kanyawara, consistent with an earlier report that fruit availability varies less at Ngogo [Chapman et al., African Journal of Ecology 35:287-302, 1997]. F. mucuso is absent at Kanyawara; its high density at Ngogo, combined with lower variation in fruit availability, probably helps to explain why chimpanzee population density is much higher at Ngogo.     

Role of the outer tissue in abscisic acid-mediated growth suppression of etiolated squash hypocotyl segments

Exogenously applied abscisic acid (ABA) substantially suppressed the elongation of hypocotyl segments of etiolated squash ( Cucurbita maxima Duch. cv. Houkou-Aokawaamaguri) after a 3 h lag period, without changes in the osmolalities of the apoplastic and symplastic solutions in the segment.
Segments with the outer tissues removed elongated more rapidly than unpeeled segments (whole segments). ABA did not suppress the elongation of peeled segments. When the segments were incubated in [¹⁴C]-glucose, radioactivity was more effectively incorporated into the cell wall fractions of the outer than into those of the inner tissue. ABA significantly inhibited the incorporation of radioactivity into hermicellulose and cellulose of the outer tissue prior to the suppression of segment elongation, but it did not inhibit the incorporation into the pectic traction of the outer tissue or into any of the cell wall fractions of the inner tissue. These results indicate that ABA primarily affected the outer tissue, in which it specifically reduced the synthesis of hemicellulose and cellulose prior to the ABA-mediated suppression of growth.     

Dynamic intracellular reorganization of cytoskeletons and the vacuole in defense responses and hypersensitive cell death in plants

Plants have evolved various means for controlled and organized cell destruction, known as programmed cell death (PCD). In plant immune responses against microbial infection, hypersensitive cell death as a form of PCD is a crucial event to prevent the spread of biotrophic pathogens. Recent live cell imaging techniques have revealed dynamic features and significant roles of cytoskeletons and the vacuole during defense responses and the PCD. Actin microfilaments (MFs) focus on the infection sites and function as tracks for the polar transport of antimicrobial materials. To accomplish hypersensitive cell death, further dynamic changes in cytoskeletons are induced. MFs play a role in the structural and functional regulation of the vacuole, leading to execution of the PCD. We here overview spatiotemporal dynamic changes in the cytoskeletons and the vacuoles triggered by signals from pathogens, and propose a hypothetical model for MF-regulated vacuole-mediated PCD in plant immunity.     

Absence of the candidate male sex-determining gene dmrt1b(Y) of medaka from other fish species

Although the sex-determining genes are known in mammals, Drosophila, and C. elegans, little is known in other animals. Fishes are an attractive group of organisms for studying the evolution of sex determination because they show an amazing variety of mechanisms, ranging from environmental sex determination and different forms of hermaphroditism to classical sex chromosomal XX/XY or WZ/ZZ systems and modifications thereof. In the fish medaka, dmrt1b(Y) has recently been found to be the candidate male sex-determining gene. It is a duplicate of the autosomal dmrt1a gene, a gene acting in the sex determination/differentiation cascade of flies, worms, and mammals. Because in birds dmrt1 is located on the Z-chromosome, both findings led to the suggestion that dmrt1b(Y) is a "non-mammalian Sry" with an even more widespread distribution. However, although Sry was found to be the male sex-determining gene in the mouse and some other mammalian species, in some it is absent and has obviously been replaced by other genes that now fulfil the same function. We have asked if the same might be true of the dmrt1b(Y) gene. We find that the gene duplication generating dmrt1b(Y) occurred recently during the evolution of the genus Oryzias. The gene is absent from all other fish species studied. Therefore, it may not be the male-sex determining gene in all fishes.     

Conformational Change of the L-Shaped tRNAPhe Molecule

Abstract

Fluorophore of proflavine was introduced onto the 3′-terminal ribose moiety of yeast tRNA^Phe. The distance between the fluorophore and the fluorescent Y base in the anticodon of yeast tRNA^Phe was measured by a singlet-singlet energy transfer. Conformational changes of tRNA^Phe with binding of tRNA^Glu ₂, which has the anticodon UUC complementary to the anticodon GAA of tRNA^Phe, were investigated. The distance obtained at the ionic strength of 100 mM K⁺ and 10 mM Mg²⁺ is very close to the distance from x-ray diffraction, while the distance obtained in the presence of tRNA^Glu ₂ is significantly smaller. Further, using a fluorescent probe of 4-bromomethl-7-methoxycoumarin introduced onto pseudouridine residue Ψ₅₅ in the TΨC loop of tRNA^Phe, Stern-Volmer quenching experiments for the probe with or without added tRNA^Glu ₂were carried out. The results showed greater access of the probe to the quencher with added tRNA^Glu ₂. These results suggest that both arms of the L-shaped tRNA structure tend to bend inside with binding of tRNA^Glu ₂ and some structural collapse occurs at the corner of the L-shaped structure.     

Modification of cell wall architecture of wheat coleoptiles grown under hypergravity conditions.

Cell wall structure of wheat coleoptiles grown under continuous hypergravity (300 g) conditions was investigated. Length of coleoptiles exposed to hypergravity for 2-4 days from germination stage was 60-70% of that of 1 g control. The amounts of cell wall polysaccharides substantially increased during the incubation period both in 1 g control and hypergravity-treated coleoptiles. As a results, the levels of cell wall polysaccharides per unit length of coleoptile, which mean the thickness of cell walls, largely increased under hypergravity conditions. The major sugar components of the hemicellulose fraction, a polymer fraction extracted from cell walls with strong alkali, were arabinose (Ara), xylose (Xyl) and glucose (Glc). The molar ratios of Ara and Xyl to Glc in hypergravity-treated coleoptiles were higher than those in control coleoptiles. Furthermore, the fractionation of hemicellulosic polymers into the neutral and acidic polymers by the anion-exchange column showed that the levels of acidic polymers in cell walls of hypergravity-treated coleoptiles were higher than those of control coleoptiles. These results suggest that hypergravity stimuli bias the synthesis of hemicellulosic polysaccharides and increase the proportion of acidic polymers, such as arabinoxylans, in cell walls of wheat coleoptiles. These structural changes in cell walls may contribute to plant resistance to hypergravity stimuli.     

Xylem water-conducting patterns of 34 broadleaved evergreen trees in southern Japan

A dye injection method was used to elucidate the xylem water-conducting pathways of 34 broadleaved evergreen trees growing in southern Japan: two semi-ring-porous, 26 diffuse-porous, five radial-porous and one non-vessel species. The large earlywood vessels in semi-ring-porous species have a water transport function in only the outermost annual ring, as in deciduous ring-porous species. On the other hand, the small vessels in semi-ring-porous species maintain the water transport function in many outer annual rings. For the other xylem-type species, the many vessels in many outer annual rings have a water transport function. In diffuse-porous species, we categorized the water-conducting pattern within the annual rings into two types: d1 type, where water travels through vessels in the whole region; and d2 type, where water travels mainly through the earlywood vessels. The pattern in radial-porous species is similar to that in the d1 type; the pattern in non-vessels species is similar to that in the d2 type. The vessel diameter in radial-porous species is similar to that of the earlywood vessels of semi-ring-porous species. These results suggest that the conduit diameter size is only one of many factors determining the water-conducting pathways of broadleaved evergreen species.     

Metabolic regulation analysis of wild-type and arcA mutant Escherichia coli under nitrate conditions using different levels of omics data

It is of practical interest to investigate the effect of nitrates on bacterial metabolic regulation of both fermentation and energy generation, as compared to aerobic and anaerobic growth without nitrates. Although gene level regulation has previously been studied for nitrate assimilation, it is important to understand this metabolic regulation in terms of global regulators. In the present study, therefore, we measured gene expression using DNA microarrays, intracellular metabolite concentrations using CE-TOFMS, and metabolic fluxes using the (13)C-labeling technique for wild-type E. coli and the ΔarcA (a global regulatory gene for anoxic response control, ArcA) mutant to compare the metabolic state under nitrate conditions to that under aerobic and anaerobic conditions without nitrates in continuous culture conditions at a dilution rate of 0.2 h(-1). In wild-type, although the measured metabolite concentrations changed very little among the three culture conditions, the TCA cycle and the pentose phosphate pathway fluxes were significantly different under each condition. These results suggested that the ATP production rate was 29% higher under nitrate conditions than that under anaerobic conditions, whereas the ATP production rate was 10% lower than that under aerobic conditions. The flux changes in the TCA cycle were caused by changes in control at the gene expression level. In ΔarcA mutant, the TCA cycle flux was significantly increased (4.4 times higher than that of the wild type) under nitrate conditions. Similarly, the intracellular ATP/ADP ratio increased approximately two-fold compared to that of the wild-type strain.     

The red clover necrotic mosaic virus RNA2 trans-activator is also a cis-acting RNA2 replication element

The expression of the coat protein gene requires RNA-mediated trans-activation of subgenomic RNA synthesis in Red clover necrotic mosaic virus (RCNMV), the genome of which consists of two positive-strand RNAs, RNA1 and RNA2. The trans-acting RNA element required for subgenomic RNA synthesis from RNA1 has been mapped previously to the protein-coding region of RNA2, whereas RNA2 is not required for the replication of RNA1. In this study, we investigated the roles of the protein-coding region in RNA2 replication by analyzing the replication competence of RNA2 mutants containing deletions or nucleotide substitutions. Our results indicate that the same stem-loop structure (SL2) that functions as a trans-activator for RNA-mediated coat protein expression is critically required for the replication of RNA2 itself. Interestingly, however, disruption of the RNA-RNA interaction by nucleotide substitutions in the region of RNA1 corresponding to the SL2 loop of RNA2 does not affect RNA2 replication, indicating that the RNA-RNA interaction is not required for RNA2 replication. Further mutational analysis showed that, in addition to the stem-loop structure itself, nucleotide sequences in the stem and in the loop of SL2 are important for the replication of RNA2. These findings suggest that the structure and nucleotide sequence of SL2 in RNA2 play multiple roles in the virus life cycle.