Paternity of Subordinates Raises Cooperative Effort in Cichlids

Background In cooperative breeders, subordinates generally help a dominant breeding pair to raise offspring. Parentage studies have shown that in several species subordinates can participate in reproduction. This suggests an important role of direct fitness benefits for cooperation, particularly where groups contain unrelated subordinates. In this situation parentage should influence levels of cooperation. Here we combine parentage analyses and detailed behavioural observations in the field to study whether in the highly social cichlid Neolamprologus pulcher subordinates participate in reproduction and if so, whether and how this affects their cooperative care, controlling for the effect of kinship. Methodology/Principal Findings We show that: (i) male subordinates gained paternity in 27.8% of all clutches and (ii) if they participated in reproduction, they sired on average 11.8% of young. Subordinate males sharing in reproduction showed more defence against experimentally presented egg predators compared to subordinates not participating in reproduction, and they tended to stay closer to the breeding shelter. No effects of relatedness between subordinates and dominants (to mid-parent, dominant female or dominant male) were detected on parentage and on helping behaviour. Conclusions/Significance This is the first evidence in a cooperatively breeding fish species that the helping effort of male subordinates may depend on obtained paternity, which stresses the need to consider direct fitness benefits in evolutionary studies of helping behaviour

Proteomic Interrogation of Human Chromatin

Chromatin proteins provide a scaffold for DNA packaging and a basis for epigenetic regulation and genomic maintenance. Despite understanding its functional roles, mapping the chromatin proteome (i.e. the “Chromatome”) is still a continuing process. Here, we assess the biological specificity and proteomic extent of three distinct chromatin preparations by identifying proteins in selected chromatin-enriched fractions using mass spectrometry-based proteomics. These experiments allowed us to produce a chromatin catalog, including several proteins ranging from highly abundant histone proteins to less abundant members of different chromatin machinery complexes. Using a Normalized Spectral Abundance Factor approach, we quantified relative abundances of the proteins across the chromatin enriched fractions giving a glimpse into their chromosomal abundance. The large-scale data sets also allowed for the discovery of a variety of novel post-translational modifications on the identified chromatin proteins. With these comparisons, we find one of the probed methods to be qualitatively superior in specificity for chromatin proteins, but inferior in proteomic extent, evidencing a compromise that must be made between biological specificity and broadness of characterization. Additionally, we attempt to identify proteins in eu- and heterochromatin, verifying the enrichments by characterizing the post-translational modifications detected on histone proteins from these chromatin regions. In summary, our results provide insights into the value of different methods to extract chromatin-associated proteins and provide starting points to study the factors that may be involved in directing gene expression and other chromatin-related processes

Characterization of an Arabidopsis mutant deficient in gamma-tocopherol methyltransferase

Alpha-tocopherol (vitamin E) is synthesized from gamma-tocopherol in chloroplasts by gamma-tocopherol methyltransferase (gamma-TMT; VTE4). Leaves of many plant species including Arabidopsis contain high levels of alpha-tocopherol, but are low in gamma-tocopherol. To unravel the function of different forms of tocopherol in plants, an Arabidopsis plant (vte4-1) carrying a functional null mutation in the gene gamma-TMT was isolated by screening a mutant population via thin-layer chromatography. A second mutant allel (vte4-2) carrying a T-DNA insertion in the coding sequence of gamma-TMT was identified in a T-DNA tagged mutant population. In vte4-1 and vte4-2 leaves, high levels of gamma-tocopherol accumulated, whereas alpha-tocopherol was absent indicating that, presumably, these two mutants represents null alleles. Over-expression of the gamma-TMT cDNA in vte4-1 restored wild-type tocopherol composition. Mutant plants were very similar to wild type. During oxidative stress (high light, high temperature, cold treatment) the amounts of alpha-tocopherol and gamma-tocopherol increased in wild type, and gamma-tocopherol in vte4-1. However, chlorophyll content and photosynthetic quantum yield were very similar in wild type and vte4-1, suggesting that alpha-tocopherol can be replaced by gamma-tocopherol in vte4-1 to protect the photosynthetic apparatus against oxidative stress. Fatty acid and lipid composition were very similar in WT, vte4-1 and vte1, an Arabidopsis mutant previously isolated which is completely devoid of tocopherol. Therefore, a shift in tocopherol composition or the absence of tocopherol has no major impact on the amounts of specific fatty acids or on lipid hydrolysis. [References: 43] 4

Light behind the curtain: photoregulation of nuclear architecture and chromatin dynamics in plants

Light is a powerful stimulus regulating many aspects of plant development and phenotypic plasticity. Plants sense light through the action of specialized photoreceptor protein families that absorb different wavelengths and intensities of light. Recent discoveries in the area of photobiology have uncovered photoreversible changes in nuclear organization correlated with transcriptional regulation patterns that lead to de-etiolation and photoacclimation. Novel signalling components bridging photoreceptor activation with chromatin remodelling and regulation of gene expression have been discovered. Moreover, coregulated gene loci have been shown to relocate to the nuclear periphery in response to light. The study of photoinduced changes in nuclear architecture is a flourishing area leading to major discoveries that will allow us to better understand how highly conserved mechanisms underlying genomic reprogramming are triggered by environmental and endogenous stimuli. This review aims to discuss fundamental and innovative reports demonstrating how light triggers changes in chromatin and nuclear architecture during photomorphogenesis