Innate immunity: has poplar made its BED?

The perennial plant model species Populus trichocarpa has received considerable attention in the last 5 yr because of its potential use as a bioenergy crop. The completion of its genome sequence revealed extensive homologies with the herbaceous annual species Arabidopsis thaliana. This review highlights the similarities and differences at the qualitative defence response components level, notably in putative NBS-LRR protein content and downstream defence regulators. With almost a twofold NBS-LRR gene complement compared with A. thaliana, P. trichocarpa also encodes some putative R-proteins with unusual architectures and possible DNA-binding capacity. P. trichocarpa also possesses all the known main components characteristic of TIR-NB-LRR and CC-NB-LRR signalling. However, very little has been done with regard to the components involved in the poplar qualitative response to pathogens. In addition, the relationship between plant-biotroph perception/signalling and the role of salicylic acid, an important defence compound, remains uncertain. This review aims to identify the genomic components present in poplar that could potentially participate in the qualitative response and highlights where efforts should be devoted to obtain a better understanding of the poplar qualitative defence response.     

Does the parasitic freshwater pearl mussel M. margaritifera harm its host?

Many parasites have strong negative impacts on their hosts, but the effects of single-host, non-trophically transmitted parasites can be subtle and are not well understood. We examined the physiological response of juvenile brown trout (Salmo trutta) to encystment by the parasitic larvae (glochidia) of the freshwater pearl mussel, Margaritifera margaritifera. Glochidia abundance was positively correlated to host body size and was accompanied by significant spleen enlargement at 31 days postexposure, but not before (15 days) or after (160 days). Compared to controls, encysted gill lamellae were significantly thicker and longer, and tended to have fewer mucous cells which may have facilitated encystment. There were no significant difference in mean blood haematocrit between encysted and uninfected trout, but encysted trout took c. 6 h longer to reach basal ventilation rate than controls suggesting that glochidiosis may impose a respiratory burden to brown trout. These findings may have implications for the artificial propagation of the freshwater pearl mussel because the effects of glochidia on host respiratory performance appear to be additive. Therefore, aiming for high glochidia loads may not be the best option for mussel propagation programmes, if this compromises host fitness and hence the probability of successful glochidia excystment.     

Feedback between zebra mussel selective feeding and algal composition affects mussel condition: did the regime changer pay a price for its success?

1. We investigated the role of algal composition on pumping, clearance, assimilation, pseudofaeces and faeces production, feeding time budgets, and condition of zebra mussels from spring to autumn at two sites in Saginaw Bay (Lake Huron) and one site in western Lake Erie. Size‐fractioned chlorophyll was used to distinguish between feeding on small (<53 μm) and large (>53 μm) size fractions, and mussel feeding behaviour was quantified by video observations. 2. Mussel pumping, clearance and assimilation rates varied among sites, particularly during summer, when phytoplankton composition varied considerably among sites. Lowest values were seen at the inner‐bay site of Saginaw Bay, low to moderate values at the outer‐bay site of Saginaw Bay, and high values at the Lake Erie site. Clearance, pumping and assimilation rates were all highly positively correlated (R² = 0.76) with per cent contribution of flagellates to total algal biomass and negatively correlated with per cent of Microcystis aeruginosa (R² = 0.63). The negative effects on pumping rate (as determined by clearance rate on the <53 μm fraction) of Microcystis, which occurred in the >53 μm fraction, could be mitigated by the presence of flagellates in the <53 μm fraction. 3. Visual observations of mussel feeding showed evidence for poor seston quality during summer negatively affecting feeding rates. High faeces production during times of low assimilation rate was suggestive of poor assimilation efficiency and/or viable gut passage of grazing resistant algae. Long periods of time not filtering by the mussels during some Microcystis blooms and lack of production of a filtering current during one experiment were suggestive of intoxication from microcystin or other secondary compounds. 4. Clearance and feeding rates of the mussels in Saginaw Bay were high during spring and autumn and very low in summer, particularly at the inner‐bay site. Condition of the mussels (mass : length ratio) was highest in spring and lowest during summer. This seasonal variation probably reflected high food assimilation rate during autumn and spring and low assimilation rate and reproduction during summer. The condition of mussels throughout the year was higher at the outer‐bay than the inner‐bay site, reflecting better feeding conditions at the former. Mussel selective feeding may have been responsible for the poor quality of food at the inner bay site; therefore, we postulate that a regime shift in phytoplankton composition promoted by the mussels fed back into lowered condition of the mussels.     

'Proteomineering': has the mine been excavated?

Evaluation of: Di Girolamo F, Boschetti E, Chung MC, Guadagni F, Righetti PG. 'Proteomineering' or not? The debate on biomarker discovery in sera continues. J. Proteomics 74(5), 589-594 (2011). The combinatorial peptide ligand library in association with mass spectrometry can greatly enhance the dynamic range of the analysis of low- and very low-abundance proteins constituting the vast majority of species in any sample. When compared with untreated samples, the increment in detection of low-abundance species appears to be at least fourfold. Recently, the combinatorial peptide ligand library has been challenged; however, it has been clearly demonstrated in the evaluated paper that the protocols for elution of the captured polypeptides make the difference. Therefore, the solid-phase ligand library made of hexapeptides remains a promising and unique tool for biomarker discovery.     

Cerebral small vessel disease: A glymphopathy?

Small vessel disease (SVD) is a common instigator of dementia in the aging population. The hallmarks of SVD are enlargement of the perivascular spaces and white matter hyperintensities. The latter represents local fluid accumulation in white matter that either subsides or develops into lacunar infarcts. We here propose that failure of brain fluid transport—via the glymphatic system—plays a key role in initiation and progression of SVD. Our major case for this concept is that perivascular spaces are utilized as waterways for influx of cerebrospinal fluid. Stagnation of glymphatic transport may drive loss of brain fluid homeostasis leading to transient white matter edema, perivascular dilation, and ultimately demyelination. This review will discuss how glymphatic rodent studies of hypertension and diabetes have provided new insight into the pathogenesis of SVD.     

HasIxianthes (Scrophulariaceae) lost its special bee?

Ixianthes retzioides is a rare, moderately sized, shrub with large yellow flowers that are lined with glandular trichomes. Preliminary analysis indicates that the trichomes secrete a complex mixture of lipids. Floral morphology suggests thatIxianthes should be pollinated by a large oil-collecting bee, yet only one possible candidate,Rediviva gig, is known and it occurs outside of the distributional range ofIxianthes. Despite observations ofIxianthes at different sites in different years, no oil-collecting bee has been observed visiting the flowers. This together with low fruit and seed set at the main study site suggests thatIxianthes has lost, at least locally, its specialized pollinator. Plants are self-compatible and set a limited amount of seed as a result of visits by pollen-collecting bees.     

Venus: Where has all the water gone?

Conditions on the surface of venus are reviewed and evidence for the existence of a hydrosphere assessed. Escape mechanisms are examined and found to be insufficient to explain the presumed absence of liquid water on venus. The consequences of a hot, acidic hydrosphere are explored as is marginal evidence for biological activity.Supported by research grants from National Aeronautics and Space Administration NGR 012-001-042, the Life Insurance Medical Research Foundation, and the University of Hawaii.     

The subspecies concept in butterflies: has its application in taxonomy and conservation biology outlived its usefulness?

Subspecies lie at the interface between systematics and population genetics, and represent a unit of biological organization in zoology that is widely used in the disciplines of taxonomy and conservation biology. In this review, we explore the utility of subspecies in relation to their application in systematics and biodiversity conservation, and briefly summarize species concepts and criteria for their diagnosis, particularly from an invertebrate perspective. The subspecies concept was originally conceived as a formal means of documenting geographical variation within species based on morphological characters; however, the utility of subspecies is hampered by inconsistencies by which they are defined conceptually, a lack of objective criteria or properties that serve to delimit their boundaries, and their frequent failure to reflect distinct evolutionary units according to population genetic structure. Moreover, the concept has been applied to populations largely comprising different components of genetic diversity reflecting contrasting evolutionary processes. We recommend that, under the general lineage (unified) species concept, the definition of subspecies be restricted to extant animal groups that comprise evolving populations representing partially isolated lineages of a species that are allopatric, phenotypically distinct, and have at least one fixed diagnosable character state, and that these character differences are (or are assumed to be) correlated with evolutionary independence according to population genetic structure. Phenotypic character types include colour pattern, morphology, and behaviour or ecology. Under these criteria, allopatric subspecies are a type of evolutionarily significant unit within species in that they show both neutral divergence through the effects of genetic drift and adaptive divergence under natural selection, and provide an historical context for identifying biodiversity units for conservation. Conservation of the adaptedness and adaptability of gene pools, however, may require additional approaches. Recent studies of Australian butterflies exemplify these points. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

RhoGAP: the next big thing for small mice?

The size of an organism is determined by the number and size of its constituent cells. The insulin/IGF-1 signaling systems have been long recognized to play a critical role in the determination of body size. Now the generation of mice deficient for a RhoGAP suggests that this small G protein might also regulate the growth of animals.     

Avidin-biotin technology ten years on: has it lived up to its expectations?

Following the practical success attributed to avidin-biotin technology, researchers are now returning to the basics to try to understand the structural and functional requirements for the high-affinity avidin-biotin interaction.     

A tale of terminal differentiation: IKKα, the master keratinocyte regulator

Keratinocyte differentiation is the process of cellular maturation from a mitotic state to a terminally differentiated state during which skin builds up a tough yet soft skin barrier to protect the body. Its irreversibility also allows the shedding of excessive keratinocytes, thereby maintaining skin homeostasis and preventing skin diseases. Although the entire journey of keratinocyte differentiation is intricate and not well understood, it is known that Ras is able to block keratinocyte terminal differentiation and instead induce keratinocyte proliferation and transformation. It appears that uncontrolled proliferation actually interrupts differentiation.

However, it has been unclear whether there are any innate surveillants that would be able to induce terminal differentiation by antagonizing excessive mitotic activities. Inhibitor of nuclear factor κB kinase-α (IKKα, previously known as Chuk) emerges as a master regulator in the coordinative control of keratinocyte differentiation and proliferation and as a major tumor suppressor in human and mouse skin squamous cell carcinomas. IKKα does so largely by integrating into the epidermal growth factor receptor (EGFR)/Ras/extracellular signal-regulated kinase (Erk)/EGFR ligand pathways during mitosis and differentiation. We discuss these findings herein to extend our understanding of how IKKα-mediated terminal differentiation serves as an innate surveillant in skin.     

Which locus has the oldest allele?

This paper studies aspects of the distribution of non-mutant ancestors of a sample of gametes in a two-locus infinitely-many-alleles model. The ancestral process of two gametes is considered in detail. Included are algorithms for calculating the probability that the oldest allele is from the first locus, and the expected age of the oldest allele. Extensions to an r-locus model in the cases of complete linkage and independence are also studied.     

Glycoprotein folding in the endoplasmic reticulum: a tale of three chaperones?

The endoplasmic reticulum (ER) is a major site of protein synthesis and its inside, or lumen, is a major site of protein folding. The lumen of the ER contains many folding factors and molecular chaperones, which facilitate protein folding by increasing both the rate and the efficiency of this process. Amongst the many ER folding factors, there are three components that specifically modulate the folding glycoproteins bearing N-linked carbohydrate side chains. These components are calnexin, calreticulin and ERp57, and this review focuses on the molecular basis for their capacity to influence glycoprotein folding.