Egg-to-embryo transition is driven by differential responses to Ca(2+) oscillation number

Ca(2+) oscillations and signaling represent a basic mechanism for controlling many cellular events. Activation of mouse eggs entrains a temporal series of Ca(2+)-dependent events that include cortical granule exocytosis, cell cycle resumption with concomitant decreases in MPF and MAP kinase activities, and recruitment of maternal mRNAs. The outcome is a switch in cellular differentiation, i.e., the conversion of the egg into the zygote. By activating mouse eggs with experimentally controlled and precisely defined Ca(2+) transients, we demonstrate that each of these events is initiated by a different number of Ca(2+) transients, while their completion requires a greater number of Ca(2+) transients than for their initiation. This combination of differential responses to the number of Ca(2+) transients provides strong evidence that a single Ca(2+) transient-driven signaling system can initiate and drive a cell into a new developmental pathway, as well as can account for the temporal sequence of cellular changes associated with early development.     

Mitogenomics of Vetigastropoda: insights into the evolution of pallial symmetry

The nucleotide sequences of the complete or nearly complete mitochondrial (mt) genomes of seven vetigastropods were determined: Angaria neglecta (Angarioidea), Phasianella solida (Phasianelloidea), Granata lyrata (Seguenzioidea), Tegula lividomaculata and Bolma rugosa (Trochoidea), Diodora graeca (Fissurelloidea) and Lepetodrilus schrolli (Lepetodriloidea). While the mt genomes of the superfamilies Angarioidea, Phasianelloidea, Seguenzioidea and Trochoidea conform generally to the ancestral gene order of Vetigastropoda and Gastropoda, those of the superfamilies Fissurelloidea and Lepetodriloidea have suffered important rearrangements. The gene order of the mtDNA of Chrysomallon squamiferum, a representative of Neomphalina, was also analysed since it has been proposed to be closely related to Vetigastropoda, and showed a distinct arrangement. The reconstructed phylogenies recovered Neomphalina as a distinct gastropod lineage that is the sister group (only with moderate bootstrap support) of a clade including Vetigastropoda and Neritimorpha + Caeno‐gastropoda while the relative position of Heterobranchia and Patellogastropoda in the gastropod tree could not be determined definitively due to their long branches. Within the monophyletic Vetigastropoda, the superfamily Fissurelloidea was recovered as the sister group of two lineages, one including Lepetodriloidea as the sister group of Seguenzioidea + Halitoidea, the other including Phasianelloidea, Angarioidea and Trochoidea without resolved relationships. The long branches of Fissurelloidea were found to introduce significant tree instability in phylogenetic reconstruction. The new phylogeny supports that the loss of the right pallial gill occurred multiple times in vetigastropod evolution as previously suggested and that Phasianelloidea, Angarioidea and Trochoidea radiated from a common asymmetric (single‐gilled) ancestor that lived in the middle Palaeozoic.     

Hierarchical genetic and spatial structure among varieties and populations of Hymenaea stigonocarpa (Fabaceae) in Brazilian savannah

Tree Genetics & Genomes - Tree breeders must almost always address multiple traits. That entails choosing selection methods and weighing up known or assumed economic-worth functions for traits....     

Experimental and theoretical definition of geminivirus origin of replication

Geminiviruses are plant pathogens that replicate by a rolling-circle mechanism, analogous to that used by several prokaryotic ssDNA replicons. Recent reports provide important progress in understanding the structure and functioning of replication origin from these viruses. We have used these data to propose models for the initiation of replication in dicot- and monocot-infecting geminiviruses.