Evaluating the role of ecological isolation in maintaining the species boundary between <Emphasis Type="Italic">Silene dioica</Emphasis> and <Emphasis Type="Italic">S. latifolia</Emphasis>

The relative importance of floral versus ecological isolation in preventing introgression remains unclear. This study examines whether ecological isolation can explain the continuing integrity of Silene dioica and S. latifolia where floral isolation is weak and hybrids are fully viable. Eighteen small replicate founder populations of 6 individuals (3 males and 3 females) of either S. latifolia, S. dioica or hybrids were created in woodland and in open sites in southern UK. Survival, reproduction and introgression of these populations were examined over 9 years. S. latifolia and hybrid plants suffered higher mortality than S. dioica in woodland. In open sites, there was extensive introgression, with few or no pure S. latifolia or S. dioica surviving by the end of the experiment. The experiment suggests that the integrity of S. dioica is maintained by its ability to survive in shaded habitats where S. latifolia and hybrids cannot persist. However, how S. latifolia survives as a distinct species in the study area remains a puzzle. Immigration from regions where S. latifolia occurs in isolation (i.e. large-scale ecological isolation) may balance introgression in the study area.     

Functional relatedness in the Inv/Mxi‐Spa type III secretion system family

Type III Secretion Systems (T3SSs) are structurally conserved nanomachines that span the inner and outer bacterial membranes, and via a protruding needle complex contact host cell membranes and deliver type III effector proteins. T3SS are phylogenetically divided into several families based on structural basal body components. Here we have studied the evolutionary and functional conservation of four T3SS proteins from the Inv/Mxi‐Spa family: a cytosolic chaperone, two hydrophobic translocators that form a plasma membrane‐integral pore, and the hydrophilic ‘tip complex’ translocator that connects the T3SS needle to the translocon pore. Salmonella enterica serovar Typhimurium (S. Typhimurium), a common cause of food‐borne gastroenteritis, possesses two T3SSs, one belonging to the Inv/Mxi‐Spa family. We used invasion‐deficient S. Typhimurium mutants as surrogates for expression of translocator orthologs identified from an extensive phylogenetic analysis, and type III effector translocation and host cell invasion as a readout for complementation efficiency, and identified several Inv/Mxi‐Spa orthologs that can functionally substitute for the S. Typhimurium chaperone and translocator proteins. Functional complementation correlates with amino acid sequence identity between orthologs, but varies considerably between the four proteins. This is the first in‐depth survey of the functional interchangeability of Inv/Mxi‐Spa T3SS proteins acting directly at the host‐pathogen interface.     

Alteration/deficiency in activation-3 (Ada3) plays a critical role in maintaining genomic stability

Cell cycle regulation and DNA repair following damage are essential for maintaining genome integrity. DNA damage activates checkpoints in order to repair damaged DNA prior to exit to the next phase of cell cycle. Recently, we have shown the role of Ada3, a component of various histone acetyltransferase complexes, in cell cycle regulation, and loss of Ada3 results in mouse embryonic lethality. Here, we used adenovirus-Cre-mediated Ada3 deletion in Ada3^fl/fl mouse embryonic fibroblasts (MEFs) to assess the role of Ada3 in DNA damage response following exposure to ionizing radiation (IR). We report that Ada3 depletion was associated with increased levels of phospho-ATM (pATM), γH2AX, phospho-53BP1 (p53BP1) and phospho-RAD51 (pRAD51) in untreated cells; however, radiation response was intact in Ada3^−/− cells. Notably, Ada3^−/− cells exhibited a significant delay in disappearance of DNA damage foci for several critical proteins involved in the DNA repair process. Significantly, loss of Ada3 led to enhanced chromosomal aberrations, such as chromosome breaks, fragments, deletions and translocations, which further increased upon DNA damage. Notably, the total numbers of aberrations were more clearly observed in S-phase, as compared with G₁ or G₂ phases of cell cycle with IR. Lastly, comparison of DNA damage in Ada3^fl/fl and Ada3^−/− cells confirmed higher residual DNA damage in Ada3^−/− cells, underscoring a critical role of Ada3 in the DNA repair process. Taken together, these findings provide evidence for a novel role for Ada3 in maintenance of the DNA repair process and genomic stability.     

UNC-45 is required for NMY-2 contractile function in early embryonic polarity establishment and germline cellularization in C. elegans

The Caenorhabditis elegans UNC-45 protein is required for proper body wall muscle assembly and acts as a molecular co-chaperone for type II myosins. In contrast to other body wall muscle components, UNC-45 is also abundant in the germline and embryo. We show that maternally provided UNC-45 acts with non-muscle myosin II (NMY-2) during embryonic polarity establishment, cytokinesis and germline cellularization. In embryos depleted for UNC-45, myosin contractility is eliminated resulting in embryonic defects in polar body extrusion, cytokinesis and establishment of polarity. Despite a lack of contractility in an unc-45(RNAi) embryo, NMY-2::GFP localizes to the cortex and accumulates at the presumptive cytokinetic furrow indicating that UNC-45 is not required for cortical localization. UNC-45 and NMY-2 are also required for fertility since the lack of either component results in complete sterility due to failed initiation of the cellularization furrows that separate syncytial nuclei into germ cells. In the absence of UNC-45, the actomyosin cytoskeleton does not contract despite non-functional myosin still directly binding actin. UNC-45 has been previously suggested to be required for the folding of the myosin head, and our results refine this hypothesis suggesting that UNC-45 is not required to fold or maintain the actin binding domain but is still required for myosin function.     

Does fumagillin control the recently detected invasive parasite Nosema ceranae in western honey bees (Apis mellifera)?

Western honey bee (Apis mellifera) colonies in Nova Scotia, Canada were sampled in spring and late summer 2007 to evaluate efficacy of fumagillin dicyclohexylammonium (hereafter, fumagillin) against Nosema ceranae. Colonies treated with fumagillin in September 2006 (n = 94) had significantly lower Nosema intensity in spring 2007 than did colonies that received no treatment (n = 51), but by late summer 2007 no difference existed between groups. Molecular sequencing of 15 infected colonies identified N. ceranae in 93.3% of cases, suggesting that fumagillin is successful at temporarily reducing this recent invasive parasite in western honey bees.     

The phenology and clutch size of UK Blue Tits does not differ with woodland composition

The deciduous tree-herbivorous caterpillar-insectivorous bird food chain is a well-studied system for investigating the impacts of climate change across trophic levels. To date, across Europe, most attention has focused on the impacts of increasing spring temperature on changes to phenology in Oak-dominated (Quercus spp.) woodlands. Paridae species and Pied Flycatcher Ficedula hypoleuca are the most studied secondary consumers, all of which demonstrate an advancement in reproductive phenology with increases in spring temperature. Shifts in climate and phenology may also impact on reproductive investment in clutch size, and the effects of climate on phenology and clutch size may vary depending on woodland composition. To date, the effects of among-habitat variation in phenology and reproductive investment have received little attention. Insectivorous birds inhabiting woodlands that differ in tree composition may differ in the timing of breeding, due to local tree leafing phenology acting as a cue for egg-laying date and/or clutch size. Moreover, for most insectivorous birds, woodland composition within a territory is likely to be the main determinant of food availability for both adults and chicks. Consequently, if warming springs affect the temporal patterns of food availability differently across different woodland compositions, this may affect the optimal average local phenology for nesting birds. Here, using data from 34 long-term (mean 15 years) nest monitoring sites across the UK, we investigate the effect of woodland tree composition and temperature on Blue Tit Cyanistes caeruleus first egg date (FED) and clutch size. We supplemented the nest monitoring data by quantifying woodland composition, at a site level, through modified point counts. We predict that birds breeding in woodlands with greater proportions of late-leafing species, such as Oak and Ash Fraxinus excelsior, will breed later than those breeding in woodlands with greater proportions of early-leafing species, such as Birch Betula spp. and Beech Fagus sylvatica. We found no evidence for differences in Blue Tit FED or clutch size in relation to the proportion of any of the tree species investigated, after controlling for temperature and latitude (FED: −3.4 and 2.2, clutch size: −0.4 and − 0.2 eggs for one-unit increase in temperature and latitude, respectively). In recent decades and across all sites, clutch size has decreased as spring temperatures have increased, a strategy which could allow birds flexibly to adjust their breeding phenology such that nestling demand coincides with peak food availability. The lack of an effect of woodland composition on Blue Tit phenology suggests Blue Tits do not fine-tune their reproductive phenology to the local tree composition. Whether this lack of evidence for phenological divergence is due to an absence of divergent selection on breeding phenology and clutch size or to gene flow is not clear.     

Impact of agricultural practices on the Zea mays L. endophytic community

Agricultural practices are known to alter bulk soil microbial communities, but little is known about the effect of such practices on the plant endophytic community. We assessed the influence of long-term applications (20 years) of herbicides and different fertilizer types on the endophytic community of maize plants grown in different field experiments. Nested PCR-denaturing gradient gel electrophoresis (DGGE) analyses targeting general bacteria, type I or II methanotrophs, actinomycetes, and general fungi were used to fingerprint the endophytic community in the roots of Zea mays L. Low intraplant variability (reproducible DGGE patterns) was observed for the bacterial, type I methanotroph, and fungal communities, whereas the patterns for endophytic actinomycetes exhibited high intraplant variability. No endophytic amplification product was obtained for type II methanotrophs. Cluster and stability analysis of the endophytic type I methanotroph patterns differentiated maize plants cultivated by using mineral fertilizer from plants cultivated by using organic fertilizer with a 100% success rate. In addition, lower methanotroph richness was observed for mineral-fertilized plants than for organically fertilized plants. The use of herbicides could not be traced by fingerprinting the endophytic type I methanotrophs or by evaluating any other endophytic microbial group. Our results indicate that the effect of agrochemicals is not limited to the bulk microbial community but also includes the root endophytic community. It is not clear if this effect is due to a direct effect on the root endophytic community or is due to changes in the bulk community, which are then reflected in the root endophytic community.     

Functional activity of RLIM/Rnf12 is regulated by phosphorylation-dependent nucleocytoplasmic shuttling

The X-linked gene Rnf12 encodes the ubiquitin ligase really interesting new gene (RING) finger LIM domain–interacting protein (RLIM)/RING finger protein 12 (Rnf12), which serves as a major sex-specific epigenetic regulator of female mouse nurturing tissues. Early during embryogenesis, RLIM/Rnf12 expressed from the maternal allele is crucial for the development of extraembryonic trophoblast cells. In contrast, in mammary glands of pregnant and lactating adult females RLIM/Rnf12 expressed from the paternal allele functions as a critical survival factor for milk-producing alveolar cells. Although RLIM/Rnf12 is detected mostly in the nucleus, little is known about how and in which cellular compartment(s) RLIM/Rnf12 mediates its biological functions. Here we demonstrate that RLIM/Rnf12 protein shuttles between nucleus and cytoplasm and this is regulated by phosphorylation of serine S214 located within its nuclear localization sequence. We show that shuttling is important for RLIM to exert its biological functions, as alveolar cell survival activity is inhibited in cells expressing shuttling-deficient nuclear or cytoplasmic RLIM/Rnf12. Thus regulated nucleocytoplasmic shuttling of RLIM/Rnf12 coordinates cellular compartments during mammary alveolar cell survival.     

Measuring mast seeding behavior: relationships among population variation,individual variation and synchrony

Mast seeding, or masting, is the variable production of flowers, seeds, or fruit across years more or less synchronously by individuals within a population. A critical issue is the extent to which temporal variation in seed production over a collection of individuals can be viewed as arising from a combination of individual variation and synchrony among individuals. Studies of masting typically quantify such variation in terms of the coefficient of variation (CV). In this paper we examine mathematically how the population CV relates to the mean individual CV and synchrony, concluding that the relationship is a complex one which cannot isolate an overall measure of synchrony, and involves additional factors, principally the number of plants sampled and the mean productivity per plant. Our development suggests some simple approximate relationships of population CV to individual variability, synchrony and the number of individuals. These were found to fit quite well when applied to data from 59 studies which included seed production at the individual level.