Intra-Golgi transport: a way to a new paradigm?

The morpho-functional principles of intra-Golgi transport are, surprisingly, still not clear, which is in marked contrast to our advanced knowledge of the underlying molecular machineries. Recently, the conceptual and technological hindrances that had delayed progress in this area have been disappearing, and a cluster of powerful morphological techniques has been revealing new glimpses of the organization of traffic in intact cells. Here, we discuss the new concepts around the present models of intra-Golgi transport.     

Are in vivo and in situ brain tissues mechanically similar?

Brain tissue mechanical properties have been well-characterized in vitro, and were found to be inhomogeneous, nonlinear anisotropic and influenced by neurological development and postmortem time interval prior to testing. However, brain in vivo is a vascularized tissue, and there is a paucity of information regarding the effect of perfusion on brain mechanical properties. Furthermore, mechanical properties are often extracted from preconditioned tissue, and it remains unclear if these properties are representative of non-preconditioned tissue. We present non-preconditioned (NPC) and preconditioned (PC) relaxation responses of porcine brain (N = 10) obtained in vivo, in situ and in vitro, at anterior, mid and posterior regions of the cerebral cortex during 4mm indentations at either 3 or 1 mm/s. Material property characteristics showed no dependency on the site tested, thus revealing that cortical gray matter on the parietal and frontal lobes can be considered homogenous. In most cases, preconditioning decreased the shear moduli, with a more pronounced effect in the dead (in situ and in vitro) brain. For most conditions, it was found that only the long-term time constant of relaxation (tau > 20 s) significantly decreased from in vivo to in situ modes (p < 0.02), and perfusion had no effect on any other property. These findings support the concept that perfusion does not affect the stiffness of living cortical tissue.     

Staufen: a common component of mRNA transport in oocytes and neurons?

Mammalian homologues of Staufen, a protein involved in localizing mRNAs during oogenesis and early central nervous system development in Drosophila, have been identified recently. The mammalian staufen gene encodes a protein containing several conserved double-stranded mRNA-binding domains and is expressed in hippocampal neurons. The mammalian Staufen protein forms granules that are transported to the distal dendrite during neuronal maturation. The Staufen granules colocalize with ribonuclear particles that transport mRNA to the dendrites. These findings might provide clues to a mechanism of mRNA transport conserved in mammalian neurons and Drosophila oogenesis.     

Are bacteria the third partner of theAzolla-Anabaena symbiosis?

The development of the prokaryotic colony inAzolla filiculoides indicates thatAnabaena azollae is maintained through the life cycle of the fern and present in the leaves and megasporocarps. The same biological pattern is applied to the bacteria that are also present in these structures and seems to follow a development pattern identical to the cyanobacteria and probably can be considered the third partner of this symbiotic association.     

Are body size and volatile blends honest signals in orchid bees?

Secondary sexual traits may convey reliable information about males’ ability to resist pathogens and that females may prefer those traits because their genes for resistance would be passed on to their offspring. In many insect species, large males have high mating success and can canalize more resources to the immune function than smaller males. In other species, males use pheromones to identify and attract conspecific mates, and thus, they might function as an honest indicator of a male's condition. The males of orchid bees do not produce pheromones. They collect and store flower volatiles, which are mixed with the volatile blends from other sources, like fungi, sap and resins. These blends are displayed as perfumes during the courtship. In this study, we explored the relationship between inter‐individual variation in body size and blend composition with the males’ phenoloxidase (PO) content in Euglossa imperialis. PO content is a common measure of insect immune response because melanine, its derived molecule, encapsulates parasites and pathogens. Body size and blend composition were related to bees’ phenolic PO content. The inter‐individual variation in body size and tibial contents could indicate differences among males in their skills to gain access to some compounds. The females may evaluate their potential mates through these compounds because some of them are reliable indicators of the males’ capacity to resist infections and parasites.     

The transport of monomers during lignification in plants: anything goes but how?

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Regulation and molecular mechanisms of calcium transport genes: do they play a role in calcium transport in the uterine endometrium?

Maintenance of calcium (Ca) balance in the uterus is critically important for many physiological functions, including smooth muscle contraction during embryo implantation. Ca transport genes, i.e., transient receptor potential cation channel subfamily V members 5/6 (TRPV5/6), calbindins, plasma membrane Ca(2+)-ATPase 1 (PMCA1), and NCX1/NCKX3, may play roles in the uterus for Ca transport and reproductive function. Although these Ca transport genes may have a role in Ca metabolism, their role(s) and molecular mechanisms require further elucidation. In this review, we highlight the expression and regulation of Ca transport genes in the uterus to clarify their potential role(s). Since Ca transport genes are abundantly expressed in reproductive tissues in a distinct manner, they may be involved in specific uterine functions including fetal implantation, Ca homeostasis, and endometrial cell production.     

Are tetraploids more successful? Floral signals,reproductive success and floral isolation in mixed-ploidy populations of a terrestrial orchid

Background and Aims Polyploidization, the doubling of chromosome sets, is common in angiosperms and has a range of evolutionary consequences. Newly formed polyploid lineages are reproductively isolated from their diploid progenitors due to triploid sterility, but also prone to extinction because compatible mating partners are rare. Models have suggested that assortative mating and increased reproductive fitness play a key role in the successful establishment and persistence of polyploids. However, little is known about these factors in natural mixed-ploidy populations. This study investigated floral traits that can affect pollinator attraction and efficiency, as well as reproductive success in diploid and tetraploid Gymnadenia conopsea (Orchidaceae) plants in two natural, mixed-ploidy populations.Methods Ploidy levels were determined using flow cytometry, and flowering phenology and herbivory were also assessed. Reproductive success was determined by counting fruits and viable seeds of marked plants. Pollinator-mediated floral isolation was measured using experimental arrays, with pollen flow tracked by means of staining pollinia with histological dye.Key Results Tetraploids had larger floral displays and different floral scent bouquets than diploids, but cytotypes differed only slightly in floral colour. Significant floral isolation was found between the two cytotypes. Flowering phenology of the two cytotypes greatly overlapped, and herbivory did not differ between cytotypes or was lower in tetraploids. In addition, tetraploids had higher reproductive success compared with diploids.Conclusions The results suggest that floral isolation and increased reproductive success of polyploids may help to explain their successful persistence in mixed-ploidy populations. These factors might even initiate transformation of populations from pure diploid to pure tetraploid.     

Social and biological measures of hyperactivity and inattention: Are they describing similar underlying constructs of child behavior?

Abstract

The relationship between 27 different measures of hyperactive, impulsive, and inattentive behavior, including those considered to be more objective and those considered more influenced by social factors, is examined using a normal sample of 219 Mexican children, ages 6 to 12. Measures were based on activity monitoring by accelerometry, ethological observation of attentional and movements states in the classroom, cognitive testing using the TOVA continuous performance test (CPT), and parents’ and teachers’ reports on ratings scales and symptom checklists. Factor analysis was used to examine to what degree these different measures are reporting similar underlying constructs (factors) of hyperactivity and inattention. Parent and teacher ratings appear to be describing underlying constructs that are distinct from those described by the other measures, but measures based on CPT, observation, and activity monitoring did not factor together either, nor more highly correlate to each other. Analysis combining all the measures showed that parent and teacher ratings factored together based on who was reporting the behavior, rather than the behavior being reported. The findings underscore that each type of measurement of hyperactivity, impulsivity, and inattention measures a different aspect of a complex behavioral phenomenon, rather than some better measuring than others the same underlying factor.     

Branchiobdellid annelids and their crayfish hosts: are they engaged in a cleaning symbiosis?

Branchiobdellid annelids and their freshwater crayfish hosts are generally thought to have a commensal relationship. Branchiobdellids of the genus Cambarincola exploit their hosts through a variety of mechanisms; however, an effect of branchiobdellids on crayfish has not been conclusively demonstrated. We investigated whether branchiobdellids positively affect the host crayfish Cambarus chasmodactylus in the New River, North Carolina. In a laboratory experiment, we placed 0, 3, or 6 branchiobdellids on C. chasmodactylus and observed a significant effect of branchiobdellid presence on both growth and mortality of host crayfish; crayfish with branchiobdellids exhibited faster growth and lower mortality with increasing branchiobdellid density. A tracer experiment demonstrated that branchiobdellids feed on items found in the branchial chamber of C. chasmodactylus. We hypothesize that such feeding activity by branchiobdellids reduces fouling of crayfish gills by epibionts and particulate matter and could lead to the reduced mortality and increased growth rates observed in the laboratory experiment. Specifically, Cambarincola may improve the ventilatory and excretory fitness of C. chasmodactylus by cleaning gill filaments. Field data support this hypothesis by demonstrating that branchiobdellids are found disproportionately at sites proximal to the branchial chamber in the New River. This study provides evidence that the relationship between C. chasmodactylus and Cambarincola may be a cleaning symbiosis, at least in environments where gill fouling is a problem for C. chasmodactylus.     

Endogenous NO levels regulate nodule functioning: Potential role of cGMP in nodule functioning?

Nitric oxide is a small gaseous signaling molecule which functions in the regulation of plant development and responses to biotic and abiotic stresses. Recently, we have shown that nitric oxide is required for development of functional nodules. Here, we show that inhibition of nitric oxide synthase enzymatic activity (using N_ω-nitro-L-arginine) reduces nitric oxide content in soybean root nodules and this is coupled by reduction of endogenous cyclic guanosine monophosphate content in the nodules. We postulate that the regulation of soybean nodule development by nitric oxide is transduced via cyclic guanosine monophosphate through activation of nitric oxide-responsive soluble guanylate cyclase. Furthermore, we hypothesize that this signaling cascade is mediated via modulation of the activities of antioxidant metabolic pathways.Key words: cyclic guanosine monophosphate, nitric oxide synthase, nitric oxide, nitrogen fixation, nodulation efficiency, nodule functioning, reactive oxygen species     

Evolution and diversity in the legume-rhizobium symbiosis: chaos theory?

This paper examines the general biology of mycorrhizal associations alongside the wide range of alternative trophic adaptations which higher plants may employ when competing for limited resources of specific nutrients within an ecosystem. All examples described come from highly nutrient-impoverished heathlands or open woodlands of the kwongan of southwest Australia. An account is given of the general patterns of rooting morphology and their association with various mycorrhizal and non-mycorrhizal nutrient-acquiring strategies, including various forms of parasitism, epiparasitism, autotrophy with or without mycorrhizal association. Taxonomic affinities of each grouping are examined alongside growth and life form characteristics. A case study of patterns of utilization of a specific nutrient, nitrogen in a Banksia woodland ecosystem is presented to illustrate how a multifaceted approach can be used for studying species responses and interactions. The study categorizes species according to nitrate-utilizing ability and suggests how ¹⁵N natural abundance of soil and plant components and organic solutes of nitrogen is xylem might be utilized to separate species into different trophic categories. Response of the ecosystem to fire is examined in respect of the nutritional interrelationships of component species as the ecosystem changes from being nitrate dominant immediately after fire to increasingly ammonium-producing thereafter. The paper concludes by examining generally trophic relationships within whole ecosystems and outlines some of the challenges for future research in this connection.     

Isoprene formation in Bacillus subtilis: a barometer of central carbon assimilation in a bioreactor?

Isoprene (2-methyl-1,3-butadiene) is a volatile hydrocarbon of uncertain function in Bacillus subtilis, and we hypothesized that it is an overflow metabolite produced during excess carbon utilization. Here we tested this idea for phase 2 of isoprene release, a phase that occurs during extracellular acetoin accumulation and its reassimilation. Phase 2 isoprene formation could be disrupted in three different ways, all related to acetoin metabolism. Disruption of a gene essential for acetoin biosynthesis (acetolactic acid synthase, alsS) blocked acetoin formation and led to cessation of phase 2 isoprene formation as well as a variety of pleiotropic effects related to loss of pH control. Growth of the alsS mutant with external pH control reversed most of these effects. Disruption of acetoin catabolism (acetoin dehydrogenase, acoA), also eliminated phase 2 isoprene formation and caused cells to transition directly from phase 1 to phase 3; the latter is attributed to amino acid catabolism. A third alteration of acetoin metabolism was detected in the widely used strain 168 (trpC2) but not in strain MS175, a trpC mutant constructed in the Marburg strain genetic background. Strain 168 exhibited slow acetoin assimilation compared to that of MS175 or the parental strain, with little or no isoprene formation during this growth phase. These findings support the idea that isoprene release occurs primarily when the rate of carbon catabolism exceeds anabolism and that this volatile hydrocarbon is a product of overflow metabolism when precursors are not required for higher isoprenoid biosynthesis. It is suggested that isoprene release might serve as a useful barometer of the rise and fall of central carbon fluxes during the growth of Bacillus strains in industrial bioreactors.