A global meta‐analysis of the relative extent of intraspecific trait variation in plant communities

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta‐analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole‐plant (e.g. plant height) vs. organ‐level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait‐based community and ecosystem studies.     

Potential extinction debt due to habitat loss and fragmentation in subalpine moorland ecosystems

Habitat loss and fragmentation would often induce delayed extinction, referred to as extinction debt. Understanding potential extinction debts would allow us to reduce future extinction risk by restoring habitats or implementing conservation actions. Although growing empirical evidence has predicted extinction debts in various ecosystems exposed to direct human disturbances, potential extinction debts in natural ecosystems with minimal direct human disturbance are little studied. Ongoing climate change may cause habitat loss and fragmentation, particularly in natural ecosystems vulnerable to environmental change, potentially leading to future local extinctions. Recent climate change would lead to extended growing season caused by earlier snowmelt in spring, resulting in expansion of shrubby species and thereby habitat loss and fragmentation of mountainous moorlands. We examined the potential extinction debts of species diversity and functional diversity (FD; trait variation or multivariate trait differences within a community) in subalpine moorland ecosystems subjected to few direct human disturbances. Plant species richness for all species and for moorland specialists were primarily explained by the past kernel density of focal moorlands (a proxy for spatial clustering of moorlands around them) but not the past area of the focal moorlands, suggesting potential extinction debt in subalpine moorland ecosystems. The higher kernel density of the focal moorland in the past indicates that it was originally surrounded by more neighborhood moorlands and/or had been locally highly fragmented. Patterns in current plant species richness have been shaped by the historical spatial configuration of moorlands, which have disappeared over time. In contrast, we found no significant relationships between the FD and historical and current landscape variables depicting each moorland. The prevalence of trait convergence might result in a less sensitive response of FD to habitat loss and fragmentation compared to that of species richness. Our finding has an important implication that climate change induced by human activities may threaten biodiversity in natural ecosystems through habitat loss and fragmentation.

     

Proteomic profiling reveals compartment-specific, novel functions of ascidian sperm proteins

In this study, we performed extensive proteomic analysis of sperm from the ascidian Ciona intestinalis. Sperm were fractionated into heads and flagella, followed by further separation into Triton X-100-soluble and -insoluble fractions. Proteins from each fraction and whole sperm were separated by isoelectric focusing using two different pH ranges, followed by SDS-PAGE at two different polyacrylamide concentrations. In total, 1,294 protein spots representing 304 non-redundant proteins were identified by mass spectrometry (MALDI-TOF). On comparison of the proteins in each fraction, we were able to identify the proteins specific to different sperm compartments. Further comparison with the testis proteome allowed the pairing of proteins with sperm-specific functions. Together with information on gene expression in developing embryos and adult tissues, these results provide insight into novel cellular and functional aspects of sperm proteins, such as distinct localization of actin isoforms, novel Ca(2+)-binding proteins in axonemes, localization of testis-specific serine/threonine kinase, and the presence of G-protein coupled signaling and ubiquitin pathway in sperm flagella.     

The soluble serum protein Gas6 bridges virion envelope phosphatidylserine to the TAM receptor tyrosine kinase Axl to mediate viral entry

Virus entry into cells is typically initiated by binding of virally encoded envelope proteins to specific cell surface receptors. Studying infectivity of lentivirus pseudotypes lacking envelope binding, we still observed high infectivity for some cell types. On further investigation, we discovered that this infectivity is conferred by the soluble bovine protein S in fetal calf serum, or Gas6, its human homolog. Gas6 enhances native infectivity of pseudotypes of multiple viral envelope proteins. Gas6 mediates binding of the virus to target cells by bridging virion envelope phosphatidylserine to Axl, a TAM receptor tyrosine kinase on target cells. Phagocytic clearance of apoptotic cells is known to involve bridging by Gas6. Replication of vaccinia virus, which was previously reported to use apoptotic mimicry to enter cells, is also enhanced by Gas6. These results reveal an alternative molecular mechanism of viral entry that can broaden host range and enhance infectivity of enveloped viruses.     

Small-scale, high-throughput method for plant N-glycan preparation for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis

Proteins fused to the elastin-like polypeptide (ELP) tag can be selectively separated from crude cell extract without chromatography. To avoid the interference of the ELP tag on properties of the target protein, it is necessary to remove the ELP tag from target protein by protease digestion. Therefore, an additional chromatographic purification step is required to remove the proteases, and this is time- and labor-consuming. Here we demonstrate the utility of the ELP-tagged proteases for cleavage of ELP fusion proteins, allowing one-step removal of the cleaved ELP tag and ELP-tagged proteases without chromatography.     

Intraspecific variation in temperature dependence of gas exchange characteristics among Plantago asiatica ecotypes from different temperature regimes

There are large inter- and intraspecific differences in the temperature dependence of photosynthesis, but the physiological cause of the variation is poorly understood. Here, the temperature dependence of photosynthesis was examined in three ecotypes of Plantago asiatica transplanted from different latitudes, where the mean annual temperature varies between 7.5 and 16.8 degrees C. Plants were raised at 15 or 30 degrees C, and the CO(2) response of photosynthetic rates was determined at various temperatures. When plants were grown at 30 degrees C, no difference was found in the temperature dependence of photosynthesis among ecotypes. When plants were grown at 15 degrees C, ecotypes from a higher latitude maintained a relatively higher photosynthetic rate at low measurement temperatures. This difference was caused by a difference in the balance between the capacities of two processes, ribulose-1,5-bisphosphate regeneration (J(max)) and carboxylation (V(cmax)), which altered the limiting step of photosynthesis at low temperatures. The organization of photosynthetic proteins also varied among ecotypes. The ecotype from the highest latitude increased the J(max) : V(cmax) ratio with decreasing growth temperature, while that from the lowest latitude did not. It is concluded that nitrogen partitioning in the photosynthetic apparatus and its response to growth temperature were different among ecotypes, which caused an intraspecific variation in temperature dependence of photosynthesis.     

Oral HPV infection and MHC class II deficiency (A study of two cases with atypical outcome)

Background

Major histocompatibility complex class II deficiency, also referred to as bare lymphocyte syndrome is a rare primary Immunodeficiency disorder characterized by a profondly deficient human leukocyte antigen class II expression and a lack of cellular and humoral immune responses to foreign antigens. Clinical manifestations include extreme susceptibility to viral, bacterial, and fungal infections. The infections begin in the first year of life and involve usually the respiratory system and the gastrointestinal tract. Severe malabsorption with failure to thrive ensues, often leading to death in early childhood. Bone marrow transplantation is the curative treatment.

Case reports

Here we report two cases with a late outcome MHC class II deficiency. They had a long term history of recurrent bronchopulmonary and gastrointestinal infections. Bone marrow transplantation could not be performed because no compatible donor had been identified. At the age of 12 years, they developed oral papillomatous lesions related to HPV (human papillomavirus). The diagnosis of HPV infection was done by histological examination. HPV typing performed on the tissue obtained at biopsy showed HPV type 6. The lesions were partially removed after two months of laser treatment.

Conclusions

Viral infections are common in patients with MHC class II and remain the main cause of death. Besides warts caused by HPV infection do not exhibit a propensity for malignant transformation; they can cause great psychosocial morbidity.     

Crystal structure of human mono-phosphorylated ERK1 at Tyr204

Extracellular signal-regulated kinase (ERK) is a member of the MAP kinase family, and can regulate several cellular responses. The isoforms ERK1 and ERK2 have markedly similar amino acid sequences, but exhibit distinctive physiological functions. As well as ERK2, ERK1 was auto- and mono-phosphorylated at Tyr204 in the activation loop during Escherichia coli production, resulting in basal level activity, approximately 500-fold less compared with fully-active ERK1 dual-phosphorylated at Thr202 and Tyr204. Crystal structure demonstrated that the mono-phosphorylated ERK1 kinase possessed a novel conformation distinguishable from the un-phosphorylated (inactive) and the dual-phosphorylated (full-active) forms. The characteristic structural features in both the C-helix and the activation loop likely contribute to the basal activity of the mono-phosphorylated ERK1. The structural dissection of ERK1 compared to ERK2 suggests that the structural differences in the D-motif binding site and in the backside binding site are putative targets for development of selective ERK1/ERK2 inhibitors.