Asynchrony between Host Plant and Insects-Defoliator within a Tritrophic System: The Role of Herbivore Innate Immunity

The effects of asynchrony in the phenology of spring-feeding insect-defoliators and their host plants on insects’ fitness, as well as the importance of this effect for the population dynamics of outbreaking species of insects, is a widespread and well-documented phenomenon. However, the spreading of this phenomenon through the food chain, and especially those mechanisms operating this spreading, are still unclear. In this paper, we study the effect of seasonally declined leafquality (estimated in terms of phenolics and nitrogen content) on herbivore fitness, immune parameters and resistance against pathogen by using the silver birch Betula pendula—gypsy moth Lymantria dispar—nucleopolyhedrovirus as the tritrophic system. We show that a phenological mismatch induced by the delay in the emergence of gypsy moth larvae and following feeding on mature leaves has negative effects on the female pupal weight, on the rate of larval development and on the activity of phenoloxidase in the plasma of haemolymph. In addition, the larval susceptibility to exogenous nucleopolyhydrovirus infection as well as covert virus activation were both enhanced due to the phenological mismatch. The observed effects of phenological mismatch on insect-baculovirus interaction may partially explain the strong and fast fluctuations in the population dynamics of the gypsy moth that is often observed in the studied part of the defoliator area. This study also reveals some indirect mechanisms of effect related to host plant quality, which operate through the insect innate immune status and affect resistance to both exogenous and endogenous virus.     

Humanin binds MPP8: mapping interaction sites of the peptide and protein

Humanin (HN), a 24‐amino acid peptide encoded by the mitochondrial 16S rRNA gene, was discovered by screening a cDNA library from the occipital cortex of a patient with Alzheimer's disease (AD) for a protection factor against AD‐relevant insults. Earlier, using the yeast two‐hybrid system, we have identified the M‐phase phosphoprotein 8 (MPP8) as a binding partner for HN. In the present work, we further confirmed interaction of HN with MPP8 in co‐immunoprecipitation experiments and localized an MPP8‐binding site in the region between 5 and 12 aa. of HN. We have also shown that an MPP8 fragment (residues 431–560) is sufficient to bind HN. Further studies on functional consequences of the interaction between the potential oncopetide and the oncoprotein may elucidate some aspects of the molecular mechanisms of carcinogenesis. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Single-cell analysis of the human T regulatory population uncovers functional heterogeneity and instability within FOXP3+ cells

Natural FOXP3(+)CD4(+)CD25(High) regulatory T cells are critical in immunological self-tolerance. Their characterization in humans is hindered by the failure to discriminate these cells from activated effector T cells in inflammation. To explore the relationship between FOXP3 expression and regulatory function at the clonal level, we used a single-cell cloning strategy of CD25-expressing CD4(+) T cell subsets from healthy human donors. Our approach unveils a functional heterogeneity nested within CD4(+)CD25(High)FOXP3(+) T cells, and typically not revealed by conventional bulk assays. Whereas most cells display the canonical regulatory T (T(reg)) cell characteristics, a significant proportion of FOXP3(+) T cells is compromised in its suppressive function, despite the maintenance of other phenotypic and functional regulatory T hallmark features. In addition, these nonsuppressive FOXP3(+) T cells preferentially emerge from the CD45RO(+) memory pool, and arise as a consequence of a rapid downregulation of FOXP3 expression upon T cell reactivation. Surprisingly, these dysfunctional T(reg) cells with unstable FOXP3 expression do not manifest overt plasticity in terms of inflammatory cytokine secretion. These results open a path to an extensive study of the functional heterogeneity of CD4(+)CD25(High)FOXP3(+) T(reg) cells and warrant caution in the sole use of FOXP3 as a clinical marker for monitoring of immune regulation in humans.     

A cluster of carboxylic groups in PsbO protein is involved in proton transfer from the water oxidizing complex of Photosystem II

The hypothesis presented here for proton transfer away from the water oxidation complex of Photosystem II (PSII) is supported by biochemical experiments on the isolated PsbO protein in solution, theoretical analyses of better understood proton transfer systems like bacteriorhodopsin and cytochrome oxidase, and the recently published 3D structure of PS II (Pdb entry 1S5L). We propose that a cluster of conserved glutamic and aspartic acid residues in the PsbO protein acts as a buffering network providing efficient acceptors of protons derived from substrate water molecules. The charge delocalization of the cluster ensures readiness to promptly accept the protons liberated from substrate water. Therefore protons generated at the catalytic centre of PSII need not be released into the thylakoid lumen as generally thought. The cluster is the beginning of a localized, fast proton transfer conduit on the lumenal side of the thylakoid membrane. Proton-dependent conformational changes of PsbO may play a role in the regulation of both supply of substrate water to the water oxidizing complex and the resultant proton transfer.     

Radioprotective role of cyanobacterial phycobilisomes

Cyanobacteria are thought to be responsible for pioneering dioxygen production and the so-called “Great Oxygenation Event” that determined the formation of the ozone layer and the ionosphere restricting ionizing radiation levels reaching our planet, which increased biological diversity but also abolished the necessity of radioprotection. We speculated that ancient protection mechanisms could still be present in cyanobacteria and studied the effect of ionizing radiation and space flight during the Foton-M4 mission on Synechocystis sp. PCC6803. Spectral and functional characteristics of photosynthetic membranes revealed numerous similarities of the effects of α-particles and space flight, which both interrupted excitation energy transfer from phycobilisomes to the photosystems and significantly reduced the concentration of phycobiliproteins. Although photosynthetic activity was severely suppressed, the effect was reversible, and the cells could rapidly recover from the stress. We suggest that the actual existence and the uncoupling of phycobilisomes may play a specific role not only in photo-, but also in radioprotection, which could be crucial for the early evolution of Life on Earth.