Sex ratio theory proposes that the equal sex ratio typically observed in birds and mammals is the result of natural selection. However, in species with chromosomal sex determination, the same 1 : 1 sex ratio is expected under random Mendelian segregation. Here, we present an analysis of 14 years of sex ratio data for a population of song sparrows (Melospiza melodia) on Mandarte Island, at the nestling stage and at independence from parental care. We test for the presence of variance in sex ratio over and above the binomial variance expected under Mendelian segregation, and thereby quantify the potential for selection to shape sex ratio. Furthermore, if sex ratio variation is to be shaped by selection, we expect some of this extra-binomial variation to have a genetic basis. Despite ample statistical power, we find no evidence for the existence of either genetic or environmentally induced variation in sex ratio, in the nest or at independence. Instead, the sex ratio variation observed matches that expected under random Mendelian segregation. Using one of the best datasets of its kind, we conclude that female song sparrows do not, and perhaps cannot, adjust the sex of their offspring. We discuss the implications of this finding and make suggestions for future research.

Macrophages are a heterogeneous cell population playing a pivotal role in tissue homeostasis and inflammation, and their phenotype strongly depends on the micromilieu. Despite its increasing importance as a translational animal model for human diseases, there is a considerable gap of knowledge with respect to macrophage polarization in dogs. The present study comprehensively investigated the morphologic, phenotypic, and transcriptomic characteristics of unstimulated (M0), M1- (GM-CSF, LPS, IFNγ-stimulated) and M2- (M-CSF, IL-4-stimulated)-polarized canine blood-derived macrophages in vitro. Scanning electron microscopy revealed distinct morphologies of polarized macrophages with formation of multinucleated cells in M2-macrophages, while immunofluorescence employing literature-based prototype-antibodies against CD16, CD32, iNOS, MHC class II (M1-markers), CD163, CD206, and arginase-1 (M2-markers) demonstrated that only CD206 was able to discriminate M2-macrophages from both other phenotypes, highlighting this molecule as a promising marker for canine M2-macrophages. Global microarray analysis revealed profound changes in the transcriptome of polarized canine macrophages. Functional analysis pointed out that M1-polarization was associated with biological processes such as “respiratory burst”, whereas M2-polarization was associated with processes such as “mitosis”. Literature-based marker gene selection revealed only minor overlaps in the gene sets of the dog compared to prototype markers of murine and human macrophages. Biomarker selection using supervised clustering suggested latexin (LXN) and membrane-spanning 4-domains, subfamily A, member 2 (MS4A2) to be the most powerful predicting biomarkers for canine M1- and M2-macrophages, respectively. Immunofluorescence for both markers demonstrated expression of both proteins by macrophages in vitro but failed to reveal differences between canine M1 and M2-macrophages. The present study provides a solid basis for future studies upon the role of macrophage polarization in spontaneous diseases of the dog, a species that has emerging importance for translational research.

The Arabidopsis phosphoinositide kinase PIP5K2 has been implicated in the control of membrane trafficking and is important for development and growth. In addition to cytosolic functions of phosphoinositides, a nuclear phosphoinositide system has been proposed, but evidence for nuclear phosphoinositides in plants is limited. Fluorescence-tagged variants of PIP5K2 reside in the nucleus of Arabidopsis root meristem cells, in addition to reported plasma membrane localization. Here we report on the interaction of PIP5K2 with alpha-importins and characterize its nuclear localization sequences (NLSs). The PIP5K2 sequence contains four putative NLSs (NLSa-NLSd) and only a PIP5K2 fragment containing NLSs is imported into nuclei of onion epidermis cells upon transient expression. PIP5K2 interacts physically with alpha-importin isoforms in cytosolic split-ubiquitin-based yeast two-hybrid tests, in dot-blot experiments and in immuno-pull-downs. A 27-amino-acid fragment of PIP5K2 containing NLSc is necessary and sufficient to mediate the nuclear import of a large cargo fusion consisting of two mCherry markers fused to RubisCO large subunit. Substitution of basic residues in NLSc results in reduced import of PIP5K2 or other cargoes into plant nuclei. The data suggest that PIP5K2 is subject to active, alpha-importin-mediated nuclear import, consistent with a nuclear role for PIP5K2 in addition to its reported cytosolic functions. The detection of both substrate and product of PIP5K2 in plant nuclei according to reporter fluorescence and immunofluorescence further supports the notion of a nuclear phosphoinositide system in plants. Variants of PIP5K2 with reduced nuclear residence might serve as tools for the future functional study of plant nuclear phosphoinositides.

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