The Ca sensor S100A1 modulates neuroinflammation,histopathology and Akt activity in the PSAPP Alzheimer's disease mouse model

The contribution of the Ca²⁺ sensor S100A1 to in vivo Alzheimer's disease (AD) pathobiology has not been elucidated although S100A1 regulates numerous cellular processes linked to AD. This study uses genetic ablation to ascertain the effects of S100A1 on neuroinflammation, beta-amyloid (Aβ) plaque deposition and Akt activity in the PSAPP AD mouse model. PSAPP/S100A1^−/− mice exhibited decreases in astrocytosis (GFAP burden), microgliosis (Iba1 burden) and plaque load/number when compared to PSAPP/S100A1^+/+ mice at six and twelve months of age. The presence of detectable S100A1 staining in human AD specimens is consistent with a detrimental gain of S100A1 function in AD. S100A1 ablation also reduced plaque associated and increased non-plaque associated PO₄-Akt and PO₄-GSK3β staining. S100A1·Akt complexes were undetectable in PC12 cells and AD brain tissue suggesting that S100A1 indirectly modulates Akt activity. In contrast, S100A1·RyR (ryanodine receptor) complexes were present in human/mouse AD brain and exhibited Ca²⁺-dependent formation in neuronal cells. This is the first direct demonstration of an S100A1· target protein complex in tissue/cells and identifies the RyR as a primary S100A1 target protein in the brain. Collectively, these data suggest that S100A1 inhibition may be a novel strategy for normalizing aberrant Ca²⁺ signaling in AD.     

SNARE VTI13 plays a unique role in endosomal trafficking pathways associated with the vacuole and is essential for cell wall organization and root hair growth in arabidopsis

Background and Aims

Root hairs are responsible for water and nutrient uptake from the soil and their growth is responsive to biotic and abiotic changes in their environment. Root hair expansion is a polarized process requiring secretory and endosomal pathways that deliver and recycle plasma membrane and cell wall material to the growing root hair tip. In this paper, the role of VTI13 (AT3G29100), a member of the VTI vesicular soluble NSF attachment receptor (SNARE) gene family in Arabidopsis thaliana, in root hair growth is described.

Methods

Genetic analysis and complementation of the vti13 root hair phenotypes of Arabidopsis thaliana were first used to assess the role of VTI13 in root hair growth. Transgenic lines expressing a green fluorescent protein (GFP)–VTI13 construct were used to characterize the intracellular localization of VTI13 in root hairs using confocal microscopy and immunotransmission electron microscopy.

Key Results

VTI13 was characterized and genetic analysis used to show that its function is required for root hair growth. Expression of a GFP–VTI13 fusion in the vti13 mutant background was shown to complement the vti13 root hair phenotype. GFP–VTI13 localized to both the vacuole membrane and a mobile endosomal compartment. The function of VTI13 was also required for the localization of SYP41 to the trans-Golgi network. Immunohistochemical analysis indicated that cell wall organization is altered in vti13 root hairs and root epidermal cells.

Conclusions

These results show that VTI13 plays a unique role in endosomal trafficking pathways associated with the vacuole within root hairs and is essential for the maintenance of cell wall organization and root hair growth in arabidopsis.     

Genomic Evidence of Rapid and Stable Adaptive Oscillations over Seasonal Time Scales in Drosophila

In many species, genomic data have revealed pervasive adaptive evolution indicated by the fixation of beneficial alleles. However, when selection pressures are highly variable along a species'' range or through time adaptive alleles may persist at intermediate frequencies for long periods. So called “balanced polymorphisms” have long been understood to be an important component of standing genetic variation, yet direct evidence of the strength of balancing selection and the stability and prevalence of balanced polymorphisms has remained elusive. We hypothesized that environmental fluctuations among seasons in a North American orchard would impose temporally variable selection on Drosophila melanogaster that would drive repeatable adaptive oscillations at balanced polymorphisms. We identified hundreds of polymorphisms whose frequency oscillates among seasons and argue that these loci are subject to strong, temporally variable selection. We show that these polymorphisms respond to acute and persistent changes in climate and are associated in predictable ways with seasonally variable phenotypes. In addition, our results suggest that adaptively oscillating polymorphisms are likely millions of years old, with some possibly predating the divergence between D. melanogaster and D. simulans. Taken together, our results are consistent with a model of balancing selection wherein rapid temporal fluctuations in climate over generational time promotes adaptive genetic diversity at loci underlying polygenic variation in fitness related phenotypes.     

QTL analysis of canning quality and color retention in black beans (Phaseolus vulgaris L.)

Black bean (Phaseolus vulgaris L.) consumption is increasing in the USA. One of the major challenges faced by breeders is to develop superior black bean cultivars to meet the demands of the canning industry. Processors require beans that take up water quickly during pre-canning soak and beans that retain their black color after canning. To properly assess canning quality requires expensive and detailed measurements of the canned product, often not possible for bean breeders. The objective of this research was identify quantitative trait loci (QTL) in a black bean recombinant inbred line (RIL) population for canning quality traits related to water uptake, color retention, and anthocyanin concentration. The parental lines from which the population was developed, Black Magic and Shiny Crow, contrasted in water uptake and color retention. These cultivars also differed in seed coat luster, controlled by a single gene, Asp. A medium-density linkage map of 1,449 markers and a distance of 1,660 cM was developed from this RIL population. The map was aligned to the bean genome sequence V1.0 by using sequence information associated with the Diversity Arrays Technology markers. QTL analysis revealed that the region near the Asp gene on chromosome Pv 07 is the major determinant of water uptake, explaining up to 49 % of the phenotypic variation. A group of QTL for color retention-related traits was found at the upper region of Pv 11, explaining up to 30 % of the phenotypic variation. A smaller effect QTL clustered on Pv 5 co-localized with a QTL for canned bean anthocyanin concentration and explained less than 10 % of the phenotypic variation. These color-related QTL have marker-assisted selection potential for bean breeders interested in enhancing color retention and anthocyanin concentration of processed black beans.     

Evolutionary responses to global change: lessons from invasive species

Biologists have recently devoted increasing attention to the role of rapid evolution in species' responses to environmental change. However, it is still unclear what evolutionary responses should be expected, at what rates, and whether evolution will save populations at risk of extinction. The potential of biological invasions to provide useful insights has barely been realised, despite the close analogies to species responding to global change, particularly climate change; in both cases, populations encounter novel climatic and biotic selection pressures, with expected evolutionary responses occurring over similar timescales. However, the analogy is not perfect, and invasive species are perhaps best used as an upper bound on expected change. In this article, we review what invasive species can and cannot teach us about likely evolutionary responses to global change and the constraints on those responses. We also discuss the limitations of invasive species as a model and outline directions for future research.     

Long-Term Citizen-Collected Data Reveal Geographical Patterns and Temporal Trends in Lake Water Clarity

We compiled a lake-water clarity database using publically available, citizen volunteer observations made between 1938 and 2012 across eight states in the Upper Midwest, USA. Our objectives were to determine (1) whether temporal trends in lake-water clarity existed across this large geographic area and (2) whether trends were related to the lake-specific characteristics of latitude, lake size, or time period the lake was monitored. Our database consisted of >140,000 individual Secchi observations from 3,251 lakes that we summarized per lake-year, resulting in 21,020 summer averages. Using Bayesian hierarchical modeling, we found approximately a 1% per year increase in water clarity (quantified as Secchi depth) for the entire population of lakes. On an individual lake basis, 7% of lakes showed increased water clarity and 4% showed decreased clarity. Trend direction and strength were related to latitude and median sample date. Lakes in the southern part of our study-region had lower average annual summer water clarity, more negative long-term trends, and greater inter-annual variability in water clarity compared to northern lakes. Increasing trends were strongest for lakes with median sample dates earlier in the period of record (1938–2012). Our ability to identify specific mechanisms for these trends is currently hampered by the lack of a large, multi-thematic database of variables that drive water clarity (e.g., climate, land use/cover). Our results demonstrate, however, that citizen science can provide the critical monitoring data needed to address environmental questions at large spatial and long temporal scales. Collaborations among citizens, research scientists, and government agencies may be important for developing the data sources and analytical tools necessary to move toward an understanding of the factors influencing macro-scale patterns such as those shown here for lake water clarity.     

The Variable Hinge Region of Novel PKCs Determines Localization to Distinct Regions of the Immunological Synapse

The immunological synapse (IS) formed between a T cell and its cognate antigen-presenting cell (APC) enables the directional secretion of cytolytic and inflammatory molecules. Synaptic architecture is established in part by a two-step cascade of novel protein kinase C (nPKC) isozymes. PKCε and PKCη arrive at the IS first, and occupy the entire synaptic membrane. Then, PKCθ accumulates in a smaller zone at the center of the contact. We investigated the molecular basis for this differential recruitment behavior using chimeric nPKC constructs and total internal reflection fluorescence microscopy. Our studies revealed that the V3 linker just N-terminal to the kinase domain plays a crucial role in specifying nPKC localization. Substitution of this linker switched the scope and the kinetics of PKCθ accumulation to that of PKCε and PKCη, and vice versa. Although the V3 was necessary for synaptic compartmentalization, it was not sufficient, as the tandem C1 domains were also required to mediate membrane association. Together, these results suggest a model whereby the V3 linker controls nPKC sub-compartmentalization after initial C1 domain-mediated accumulation at the IS.     

Environmental heterogeneity,multivariate sexual selection and genetic constraints on cuticular hydrocarbons in Drosophila simulans

Sexual selection is responsible for the evolution of many elaborate traits, but sexual trait evolution could be influenced by opposing natural selection as well as genetic constraints. As such, the evolution of sexual traits could depend heavily on the environment if trait expression and attractiveness vary between environments. Here, male Drosophila simulans were reared across a range of diets and temperatures, and we examined differences between these environments in terms of (i) the expression of male cuticular hydrocarbons (CHCs) and (ii) which male CHC profiles were most attractive to females. Temperature had a strong effect on male CHC expression, whereas the effect of diet was weaker. Male CHCs were subject to complex patterns of directional, quadratic and correlational sexual selection, and we found differences between environments in the combination of male CHCs that were most attractive to females, with clearer differences between diets than between temperatures. We also show that genetic covariance between environments is likely to cause a constraint on independent CHC evolution between environments. Our results demonstrate that even across the narrow range of environmental variation studied here, predicting the outcome of sexual selection can be extremely complicated, suggesting that studies ignoring multiple traits or environments may provide an over‐simplified view of the evolution of sexual traits.     

The ARC1 E3 Ligase Promotes a Strong and Stable Self-Incompatibility Response in Arabidopsis Species: Response to the Nasrallah and Nasrallah Commentary

Following the identification of the male (S-locus Cysteine Rich/S-locus Protein 11) and female (S Receptor kinase [SRK]) factors controlling self-incompatibility in the Brassicaceae, research in this field has focused on understanding the nature of the cellular responses activated by these regulators. We previously identified the ARM Repeat Containing1 (ARC1) E3 ligase as a component of the SRK signaling pathway and demonstrated ARC1’s requirement in the stigma for self-incompatible pollen rejection in Brassica napus, Arabidopsis lyrata, and Arabidopsis thaliana. Here, we discuss our findings on the role of ARC1 in reconstructing a strong and stable A. thaliana self-incompatibility phenotype, in the context of the putative issues outlined in a commentary by Nasrallah and Nasrallah. Additionally, with their proposed standardized strategy for studying self-incompatibility in A. thaliana, we offer our perspective on what constitutes a strong and stable self-incompatibility phenotype in A. thaliana and how this should be investigated and reported to the greater community.With many angiosperms possessing hermaphroditic flowers, self-incompatibility (SI) systems have evolved to avoid the deleterious effects of inbreeding (Figures 1A and 1B). As defined by Charlesworth et al. (2005), “plant SI systems all prevent self-fertilization through recognition and rejection of pollen by pistils expressing ‘cognate’ allelic specificity.” In Brassicaceae species, the allele specificity is conferred by two well-characterized polymorphic genes encoding the female S Receptor kinase (SRK) and the male S-locus Protein 11/S-locus Cysteine Rich (SP11/SCR; hereby referred to as SCR) (reviewed in Iwano and Takayama, 2012). The major outstanding area in this field is identifying the signaling proteins activated by SRK, determining their function at the cellular level, and investigating whether these signaling proteins have conserved functions across the self-incompatible species in the Brassicaceae. Despite strong interest in finding these potential factors by us and other groups, only the Brassica rapa M Locus Protein Kinase (Murase et al., 2004; Kakita et al., 2007a, 2007b) and the ARM Repeat Containing1 (ARC1) E3 ligase have emerged as direct downstream signaling proteins. We demonstrated a conserved role for ARC1 in self-incompatible Brassica napus (Gu et al., 1998; Stone et al., 1999, 2003), self-incompatible Arabidopsis lyrata (Indriolo et al., 2012), and self-incompatible Arabidopsis thaliana expressing A. lyrata SCRb, SRKb, and ARC1 transgenes (Indriolo et al., 2014). The commentary by Nasrallah and Nasrallah (2014) focuses on our proposed role for ARC1 in reconstituting self-incompatibility in transgenic A. thaliana.Open in a separate windowFigure 1.Pathways for Compatible and Self-Incompatible Pollen Responses in A. thaliana.(A) Compatible (arrow) and self-incompatible (bar) pollen-pistil interactions.(B) Criteria for assessing compatible versus self-incompatible pollinations.(C) Model for the basal compatible pollen response. An unknown basal pollen response pathway is activated in the stigmatic papilla under the compatible pollen grain leading to the activation of vesicle secretion. Our research on Brassica and Arabidopsis Exo70A1 revealed a putative role for the exocyst complex in docking secretory vesicles at the stigmatic papillae plasma membrane (Samuel et al., 2009; Safavian and Goring, 2013; Safavian et al., 2014). Exo70A1 is proposed to assemble with the remaining subunits of the exocyst complex to dock secretory vesicles (reviewed in Zárský et al., 2013). SNARE proteins mediate vesicle fusion to the plasma membrane, and unknown cargo (ACA13 as one candidate; Iwano et al., 2014) are released to enable pollen hydration pollen tube entry through the stigmatic papillar cell wall (compatible pollen is accepted).(D) Model for the reconstituted self-incompatibility signaling pathway in the Sha ecotype. Following self-pollination in transgenic SCR-SRK+ARC1 Sha ecotype flowers, the pollen SCR ligand binds to SRK at the stigmatic papillar plasma membrane, resulting in the activation of the downstream signaling pathway. The ARC1 E3 ligase is recruited by SRK and targets Exo70A1 for ubiquitination. Even though the basal compatible pollen response pathway has been also activated, ubiquitinated Exo70A1 is somehow inhibited so that exocyst-mediated vesicle secretion to the self-incompatible pollen grain is blocked. In addition, secretory vesicles are degraded in the vacuole through autophagy. An unknown signaling protein (yellow) also has activity in the Sha ecotype in blocking exocytosis (see Samuel et al. [2009], Safavian and Goring [2013], and Indriolo et al. [2014] for further details and references therein).(E) Transmission electron microscopy image of a self-incompatible pollen-stigmatic papillar interaction at 10 min postpollination from the transgenic SCRb-SRKb+ARC1 Sha ecotype. Pseudocoloring has been added to distinguish the pollen (brown) from the stigmatic papilla (green). Autophagy is detected with the autophagic vacuole in the vacuole (see Rose et al. [2006] and Indriolo et al. [2014] for details). (Figures 1C to 1E adapted from Indriolo et al. [2014], Figures 9 and 10.)