ALBERT

Description: Extracytoplasmic function sigma factors represent the third pillar of signal-transduction mechanisms in bacteria. The variety of stimuli they recognize and mechanisms of action they use have allowed their classification into more than 50 groups. We have characterized CorE2 from Myxococcus xanthus , which belongs to group ECF44 and upregulates the expression of two genes when it is activated by cadmium and zinc. Sigma factors of this group contain a Cys-rich domain (CRD) at the C terminus which is essential for detecting metals. Point mutations at the six Cys residues of the CRD have revealed the contribution of each residue to CorE2 activity. Some of them are essential, while others are either dispensable or their mutations only slightly affect the activity of the protein. However, importantly, mutation of Cys174 completely shifts the specificity of CorE2 from cadmium to copper, indicating that the Cys arrangement of the CRD determines the metal specificity. Moreover, the conserved CxC motif located between the 2 domain and the 4.2 region has also been found to be essential for activity. The results presented here contribute to our understanding of the mechanism of action of metal-dependent sigma factors and help to define new common features of the members of this group of regulators.

Description: IntroductionMorphological integration and modularity depend on genetic covariation between traits, which emerges from pleiotropic effects of single loci and genetic linkage between loci. Since chromosomal reorganizations alter meiotic recombination, they might modify groups of linked genes and entail the fixation of new alleles with new pleiotropic effects. As a result, they could contribute to the intraspecific variation of the covariance structure of morphological traits. Although the mouse mandible has long been studied in terms of development and evolution, little is known about how its covariance structure varies in natural populations with chromosomal reorganizations. Consequently, here we analyzed the magnitude and patterns of morphological covariation of mandible shape in groups of mice with different karyotypes from a Robertsonian system of Mus musculus domesticus. Results: The organization of the mouse mandible into two main modules was confirmed in all chromosomal groups, since RV coefficients for the corresponding subdivision of landmarks were always significant. However, substantial variation in the magnitude of integration was detected between groups, especially when the effect of allometry was not removed. A significant positive correlation between differences in magnitude of integration of the symmetric component of shape and karyotypic distances between groups was detected when not correcting for size. Moreover, the degree of dependence of symmetric shape variation on size showed a negative association with the chromosome number and a positive association with the magnitude of integration. All groups showed similar patterns of morphological integration of the mandible, especially regarding the symmetric component of shape. However, the display of landmark displacements and the computation of vector angles highlighted some differences. In addition, distances between groups in terms of covariation matrices of the symmetric component were positively correlated with geographic distance. Conclusions: Robertsonian translocations do not alter the organization of the mouse mandible into two main modules, but do affect the magnitude of integration between them. This effect is mainly due to changes in the allometric relationship. In the ‘Barcelona’ Robertsonian system, geographically structured sources of variation seem to affect the patterns of integration by producing parallel variation in separate developmental pathways. Overall, our results suggest that Robertsonian translocations could play a role in intraspecific differentiation processes by producing changes in the covariance structure of morphological traits.

Description: Background: Modularity is an important feature in the evolvability of organisms, since it allows the occurrence of complex adaptations at every single level of biological systems. While at the cellular level the modular organization of molecular interactions has been analyzed in detail, the phenotypic modularity (or variational modularity) of cell shape remains unexplored. The mammalian spermatozoon constitutes one of the most complex and specialized cell types found in organisms. The structural heterogeneity found in the sperm head suggests an association between its inner composition, shape and specificity of function. However, little is known about the extent of the connections between these features. Taking advantage of the mouse sperm morphology, we analyzed the variational modularity of the sperm head by testing several hypotheses related to its structural and functional organization. Because chromosomal rearrangements can affect the genotype-phenotype map of individuals and thus modify the patterns of covariation between traits, we also evaluate the effect of Robertsonian translocations on the modularity pattern of the sperm head. Results: The results indicated that the mouse sperm head is divided into three variational modules (the acrosomal, post-acrosomal and ventral spur module), which correspond to the main regions of the cytoskeletal mesh beneath the plasma membrane, i.e., the perinuclear theca. Most of the covariation is concentrated between the ventral spur and the acrosomal and post-acrosomal modules. Although the Rb fusions did not alter the main modularity pattern, they did affect the percentages of covariation between pairs of modules. Conclusions: The structural heterogeneity of the cytoskeleton is responsible for the modular organization of the sperm head shape, corroborating the role that this structure has in maintaining the cell shape. The reduction in percentages of shape covariation between pairs of modules in Rb sperms suggests that chromosomal rearrangements could induce changes in the genotype-phenotype map. Nevertheless, how these variations affect sperm fertilization success is yet to be elucidated.

Description: Background: Thiazolidinedione are antidiabetic agents that increase insulin sensitivity but reduce glucoseoxidation, state 3 respiration, and activity of complex I of the mitochondrial respiratory chain(MRC). Mechanisms of the latter effects are unclear. The aim of this study was to determinethe mechanisms by which pioglitazone (PGZ), a member of the thiazolidinedione class ofantidiabetic agents, decreases the activity of MRC. In isolated mitochondria from mouseliver, we measured the effects of PGZ treatment on MRC complexes activity, fully-assembledcomplex I and its subunits, gene expression of complex I and III subunits, and [3H]pioglitazone binding to mitochondrial complexes. Results: (1) In vitro, PGZ decreased activity of complexes I and III of the MRC, but in vivo onlycomplex I activity was decreased in mice treated for 12 weeks with 10 mg/Kg/day of PGZ.(2) In vitro treatment of isolated liver mitochondria with PGZ disassembled complex Iresulting in the formation of several subcomplexes. In mice treated with PGZ, fullyassembled complex I was increased and two additional subcomplexes were found. Formationof supercomplexes CI+CIII2+CIVn and CI+CIII2 decreased in mouse liver mitochondriaexposed to PGZ, while formation of these supercomplexes was increased in mice treated withPGZ. Two dimensional analysis of complex I using BN/SDS-PAGE showed that in vitroPGZ induced the formation of four subcomplexes of 600 (B), 400 (C), 350 (D), and 250 (E)kDa, respectively. Subcomplexes B and C had NADH:dehydrogenase activity, whilesubcomplexes C and D contained subunits of complex I membrane arm. (3) Autoradiographyand coimmunoprecipitation assays showed [3H]PGZ binding to subunits NDUFA9,NDUFB6, and NDUFA6. (4) Treatment with PGZ increased mitochondrial gene transcriptionin mice liver and HepG2 cells. (5) In these cells, PGZ decreased intracellular ATP contentand enhanced gene expression of specific protein-1 and peroxisome-proliferator activatedreceptor (PPAR)-gamma coactivator-1alpha (PGC-1alpha). Conclusions: PGZ binds complex I subunits, which induces disassembly of this complex, reduces itsactivity, depletes cellular ATP, and, in mice and HepG2 cells, upregulates nuclear DNAencodedgene expression of complex I and III subunits.

Description: LAEs and LBGs represent the most common groups of star-forming galaxies at high-z, and the differences between their inherent stellar populations (SPs) are a key factor in understanding early galaxy formation and evolution. We have run a set of SP burst-like models for a sample of 1,558 sources at 3.4 〈 z 〈 6.8 from the Survey for High-z Absorption Red and Dead Sources (SHARDS) over the GOODS-N field. This work focuses on the differences between the three different observational subfamilies of our sample: LAE-LBGs, no-Lyα LBGs and pure LAEs. Single and double SP synthetic spectra were used to model the SEDs, adopting a Bayesian information criterion to analyse under which situations a second SP is required. We find that the sources are well modelled using a single SP in $sim 79{{ m per cent}}$ of the cases. The best models suggest that pure LAEs are typically young low mass galaxies ($tsim 26^{+41}_{-25}$ Myr; $M_{mathrm{star}}sim 5.6^{+12.0}_{-5.5}imes 10^{8} M_{odot }$), undergoing one of their first bursts of star formation. On the other hand, no-Lyα LBGs require older SPs (t ∼ 71 ± 12 Myr), and they are substantially more massive (Mstar ∼ 3.5 ± 1.1 × 109 M⊙). LAE-LBGs appear as the subgroup that more frequently needs the addition of a second SP, representing an old and massive galaxy caught in a strong recent star-forming episode. The relative number of sources found from each subfamily at each z supports an evolutionary scenario from pure LAEs and single SP LAE-LBGs to more massive LBGs. Stellar Mass Functions are also derived, finding an increase of M* with cosmic time and a possible steepening of the low mass slope from z ∼ 6 to z ∼ 5 with no significant change to z ∼ 4. Additionally, we have derived the SFR-Mstar relation, finding a $mathrm{SFR}propto M_{mathrm{star}}^{ eta }$ behaviour with negligible evolution from z ∼ 4 to z ∼ 6.

Description: Background Liberibacter crescens is the closest cultured relative of four important uncultured crop pathogens. Candidatus. L. asiaticus, L. americanus, L. africanus cause citrus greening disease, while Ca. L. solanacearum causes potato Zebra chip disease. None of the pathogens grows in axenic culture. L. crescens grows in three media: a BM-7, a serum-free Hi® Grace’s Insect Medium (Hi-GI), and a chemically-defined medium called M15. To date, no optimal growth parameters of the model species L. crescens have been reported. Studying the main growth parameters of L. crescens in axenic culture will give us insights into the lifestyle of the Ca. Liberibacter pathogens. Results The evaluation of the growth parameters—pH, aeration, temperature, and buffering capacity—reflects the optimal living conditions of L. crescens. These variables revealed that L. crescens is an aerobic, neutrophilic bacterium, that grows optimally in broth in a pH range of 5.8 to 6.8, in a fully oxygenated environment (250 rpm), at 28 °C, and with monosodium phosphate (10 mM or 11.69 mM) as the preferred buffer for growth. The increase of pH in the external media likely results from the deamination activity within the cell, with the concomitant over-production of ammonium in the external medium. Conclusion L. crescens and the Ca. Liberibacter pathogens are metabolically similar and grow in similar environments—the phloem and the gut of their insect vectors. The evaluation of the growth parameters of L. crescens reveals the lifestyle of Liberibacter, elucidating ammonium and phosphate as essential molecules for colonization within the hosts. Ammonium is the main driver of pH modulation by active deamination of amino acids in the L. crescens amino acid rich media. In plants, excess ammonium induces ionic imbalances, oxidative stress, and pH disturbances across cell membranes, causing stunted root and shoot growth and chlorosis—the common symptoms of HLB-disease. Phosphate, which is also present in Ca. L. asiaticus hosts, is the preferred buffer for the growth of L. crescens. The interplay between ammonium, sucrose, potassium (K+), phosphate, nitrate (NO3−), light and other photosynthates might lead to develop better strategies for disease management.