Bird-pollination of three Durio species (Bombacaceae) in a tropical rainforest in Sarawak, Malaysia

Pollination ecology of three Durio species, D. grandiflorus, D. oblongus, and D. kutejensis (Bombacaceae), was studied in a lowland dipterocarp forest in Sarawak, Malaysia, during a peak flowering period when at least 305 species of plants bloomed in 1996. Durio has been reported to be pollinated by bats in Peninsular Malaysia. However, my observations of flower visitors and pollination experiments indicated that two species, D. grandiflorus and D. oblongus, were pollinated by spiderhunters (Nectariniidae) and that the other species, D. kutejensis, was pollinated by giant honey bees and bats as well as birds. Hand-pollination experiments showed that all three species were obligate outbreeders. A resource limitation in fruit production was suggested. The former two species were visited only by spiderhunters, and the bagged flowers that were opened for animal visitors only at night bore no fruit, while those that were opened only during the day bore fruits, at comparable fruiting ratios to open pollination. Durio kutejensis was observed to be visited by giant honey bees, birds, and bats at different times of day, and three series of bagged experiments that exposed the flowers to animal visitors at different times of day bore fruits at a comparable ratio to open-pollination.     

The genetics of rust resistance in sugar cane seedling populations

The inheritance of rust resistance was studied in sugar cane seedling populations using a factorial mating design over 1 summer and 2 winter seasons. Frequency distributions for rust infection pooled over 2 winter seasons for resistant x resistant parents were highly skewed with the majority of progenies grouped towards the resistant classes, whereas crosses between susceptible x highly susceptible parents tended to be skewed with the majority of progenies grouped towards the susceptible ones. Both categories of crosses produced transgressive segregants at either extremes. Distribution of infection within progeny of the selfed resistant parent ’R 570’ and distribution in the majority of crosses tended to support the hypothesis of a major gene with a dominant effect for resistance. However, the action of other minor genes acting in a quantitative way is also suggested. The female (F) and male (M) variance components were very important, and F×M interaction indicated the existence of non-additive genetic effects. F×S, M×S and F×M×S interaction mean squares were generally low or insignificant. Broad-sense heritability for the individual season ratings and for the combined ratings was high (0.75–0.90), whereas narrow-sense heritability was generally moderate (0.40–0.52) with the additive genetic effects accounting for 44–68% of the total genetic variation. The implications of these findings in the breeding for rust resistance in the local programme are discussed. Received: 2 June 1999 / Accepted: 22 June 1999     

Identification of trophoblast-specific binding sites for GATA-2 that are essential for rat placental lactogen-I gene expression

We identified a 3.4-kb 5′-flanking region of the rPL-I gene and examined its promoter activity using rat trophoblast Rcho-1 cells. A regulatory element between base pairs (bp) −2,487 and −2,310 in the 5′-flanking region was essential for maximum promoter activity of the rPL-I gene. This regulatory element was further characterized between bp −2,443 to −2,415 and −2,374 to −2,345. Electrophoretic mobility shift analysis showed that the interaction of nuclear extract proteins from differentiated Rcho-1 cells was inhibited by competition with a GATA-like sequence in the promoter, but not by a mutated GATA sequence. Moreover, the promoter activity of 2487 eLuc containing two novel GATA sites was significantly elevated by co-transfection of a GATA-2 expression vector in proliferating Rcho-1 cells. Our results demonstrate that GATA-2 is involved in multiple promoter regions to activate the specific expression of the rPL-I gene in placental tissue. Gon-Sup Kim and Yeoung-Gyu Ko are contributed equally to this work.     

Membrane-Associated Cytoskeletal Proteins in Squid Giant Axons

Abstract: Cytoskeletal proteins (e.g., tubulin, actin, and neurofilament proteins) in the squid giant axon are separable into KF-soluble and -insoluble forms. The KF-insoluble cytoskeletal components appear to constitute the major proteins in the subaxolemmal fibrous network on the inner surface of the axon. These cytoskeletal proteins and the subaxolemmal network are both highly soluble in KI solutions. Whereas giant axons tolerate prolonged perfusions in KF solutions with no loss of excitable properties, a relatively short perfusion with KI solution completely eliminates the excitability of the axon. The loss of this excitability correlates with the simultaneous dissolution of the subaxolemmal network of cytoskeletal proteins and the release of its proteins into the perfusate. These data support the hypothesis that cytoskeletal proteins associated with the inner surface of the axolemma are involved in the regulation of axonal excitability.     

The Biology of Rotylenchulus macrodoratus

Rotylenchulus macrodoratus completed its embryogenic development in about 16-19 days at 18-32 C. On olive seedlings the life-cycle from egg to egg was completed in 45-55 days. The first molt occurred in the egg while the other three were superimposed, with retention of successive larval cuticles. Only immature vermiform and swollen egg-laying females were found attached to olive roots. Eggs are laid in a gelatinous matrix on the root surface. The maximum number of eggs seen was 55. Males were not parasitic. Dianthus barbatus, Parietaria officinalis, and Eriobotrya japonica were found to be hosts of the parasite. Observed in all infested hosts was an uninucleate giant cell that expanded from the endodermis toward the center of the stele in primary roots, and from the secondary vascular tissue toward the periphery of the cortex in secondary roots.     

Lethal (2) Giant Larvae: An Indispensable Regulator of Cell Polarity and Cancer Development

Cell polarity is one of the most basic properties of all normal cells and is essential for regulating numerous biological processes. Loss of polarity is considered a hallmark for cancer. Multiple polarity proteins are implicated in maintenance of cell polarity. Lethal (2) giant larvae (Lgl) is one of polarity proteins that plays an important role in regulating cell polarity, asymmetric division as well as tumorigenesis. Lgl proteins in different species have similar structures and conserved functions. Lgl acts as an indispensable regulator of cell biological function, including cell polarity and asymmetric division, through interplaying with other polarity proteins, regulating exocytosis, mediating cytoskeleton and being involved in signaling pathways. Furthermore, Lgl plays a role of a tumor suppressor, and the aberrant expression of Hugl, a human homologue of Lgl, contributes to multiple cancers. However, the exact functions of Lgl and the underlying mechanisms remain enigmatic. In this review, we will give an overview of the Lgl functions in cell polarity and cancer development, discuss the potential mechanisms underlying these functions, and raise our conclusion of previous studies and points of view about the future studies.     

Factors influencing detection of eDNA from a stream‐dwelling amphibian

Environmental DNA (eDNA) methods for detecting and estimating abundance of aquatic species are emerging rapidly, but little is known about how processes such as secretion rate, environmental degradation, and time since colonization or extirpation from a given site affect eDNA measurements. Using stream‐dwelling salamanders and quantitative PCR (qPCR) analysis, we conducted three experiments to assess eDNA: (i) production rate; (ii) persistence time under different temperature and light conditions; and (iii) detectability and concentration through time following experimental introduction and removal of salamanders into previously unoccupied streams. We found that 44–50 g individuals held in aquaria produced 77 ng eDNA/h for 2 h, after which production either slowed considerably or began to equilibrate with degradation. eDNA in both full‐sun and shaded treatments degraded exponentially to <1% of the original concentration after 3 days. eDNA was no longer detectable in full‐sun samples after 8 days, whereas eDNA was detected in 20% of shaded samples after 11 days and 100% of refrigerated control samples after 18 days. When translocated into unoccupied streams, salamanders were detectable after 6 h, but only when densities were relatively high (0.2481 individuals/m²) and when samples were collected within 5 m of the animals. Concentrations of eDNA detected were very low and increased steadily from 6–24 h after introduction, reaching 0.0022 ng/L. Within 1 h of removing salamanders from the stream, eDNA was no longer detectable. These results suggest that eDNA detectability and concentration depend on production rates of individuals, environmental conditions, density of animals, and their residence time.     

Coevolutionary and Phylogenetic Analysis of Mimiviral Replication Machinery Suggest the Cellular Origin of Mimiviruses

Mimivirus is one of the most complex and largest viruses known. The origin and evolution of Mimivirus and other giant viruses have been a subject of intense study in the last two decades. The two prevailing hypotheses on the origin of Mimivirus and other viruses are the reduction hypothesis, which posits that viruses emerged from modern unicellular organisms; whereas the virus-first hypothesis proposes viruses as relics of precellular forms of life. In this study, to gain insights into the origin of Mimivirus, we have carried out extensive phylogenetic, correlation, and multidimensional scaling analyses of the putative proteins involved in the replication of its 1.2-Mb large genome. Correlation analysis and multidimensional scaling methods were validated using bacteriophage, bacteria, archaea, and eukaryotic replication proteins before applying to Mimivirus. We show that a large fraction of mimiviral replication proteins, including polymerase B, clamp, and clamp loaders are of eukaryotic origin and are coevolving. Although phylogenetic analysis places some components along the lineages of phage and bacteria, we show that all the replication-related genes have been homogenized and are under purifying selection. Collectively our analysis supports the idea that Mimivirus originated from a complex cellular ancestor. We hypothesize that Mimivirus has largely retained complex replication machinery reminiscent of its progenitor while losing most of the other genes related to processes such as metabolism and translation.     

Paternity analysis in an egg‐carrying aquatic insect Appasus major (Hemiptera: Belostomatidae) using microsatellite DNA markers

The giant water bug Appasus major exhibits a peculiar reproductive behavior where females lay eggs on the backs of males. A male and female pair performs frequent repeat copulations during the oviposition behavior, and the male carries the deposited eggs until hatching. Such characteristic behaviors predict that the eggs are fertilized by the brooding males. If males carry eggs of other unrelated males, the egg carrying will drastically decrease the fitness of the carriers. In this study, we examined genetic relationships between the 489 eggs and nine males carrying them collected from the field, using microsatellite DNA markers. We revealed that in total, 28.4% of the eggs were of other male origin. This is the first report of frequent brood parasitism in an aquatic egg‐carrying hemipteran insect. The brood parasitism is adaptive for the females probably because it enables them to increase the chance of oviposition, or it can equalize motility risk of the eggs of each mate.     

Sex differences in spatial ability: a test of the range size hypothesis in the order Carnivora

Sex differences in spatial cognition have been reported for many species ranging from voles to humans. The range size hypothesis predicts that sex differences in spatial ability will only occur in species in which the mating system selects for differential range size. Consistent with this prediction, we observed sex differences in spatial ability in giant pandas, a promiscuous species in which males inhabit larger ranges than females, but did not observe sex differences in Asian small-clawed otters, a related monogamous species in which males and females share home ranges. These results provide the first evidence of sex differences in spatial ability in the order Carnivora, and are consistent with the range size hypothesis.