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We present a study of the physical properties of the disc and tail of ESO137-001, a galaxy suffering from extreme ram-pressure stripping during its infall into the Norma cluster. With sensitive and spatially resolved MUSE (Multi Unit Spectroscopic Explorer) spectroscopy, we analyse the emission line diagnostics in the tail of ESO137-001, finding high values of [N II]/Hα and [O I]/Hα that are suggestive of the presence of shocks in turbulent gas. However, the observed line ratios are not as strong as commonly seen in pure shock heating models, suggesting that other emission mechanisms may contribute to the observed emission. Indeed, part of the observed emission, particularly at close separations from the galaxy disc, may originate from recombination of photoionized gas stripped from the main body of ESO137-001. We also identify a large number of bright compact knots within in the tail, with line ratios characteristic of HII regions. These HII regions, despite residing in a stripped gas tail, have quite typical line ratios, densities, temperatures, and metallicity (~0.7 solar). The majority of these HII regions are embedded within diffuse gas from the tail, which is dynamically cool (σ ~ 25- 50 km s-1). This fact, together with a lack of appreciable gradients in age and metallicity, suggests that these HII regions formed in situ. While our analysis represents a first attempt to characterize the rich physics of the ESO137-001 tail, future work is needed to address the importance of other mechanisms, such as thermal conduction and magnetohydrodynamic waves, in powering the emission in the tail. [ABSTRACT FROM AUTHOR]

We obtained long-slit optical spectra of the nuclear regions of 376 galaxies in the local Universe using the 1.5 m Cassini telescope of Bologna Observatory. Of these spectra, 164 were either never taken before by the Sloan Digital Sky Survey (SDSS), or given by the Nasa Extragalactic Database (NED). With these new spectra, we contribute investigating the occurrence of active galactic nuclei (AGNs). Nevertheless, we stress that the present sample is by no means complete, thus, it cannot be used to perform any demographic study. Following the method used in a previous work, we classify the nuclear spectra using a six bin scheme: SEY (Seyfert), sAGN (strong AGN), and wAGN (weak AGN) represent active galactic nuclei of different levels of activity; HII accounts for star-forming nuclei; RET (retired) and PAS (passive) refer to nuclei with poor or no star-formation activity. The spectral classification is performed using the ratio of λ 6584 [NII] to Hα lines and the equivalent width (EW) of Hα versus [NII]/Hα (WHAN diagnostic introduced by Cid Fernandes and collaborators) after correcting Hα for underlying absorption. The obtained spectra are made available in machine readable format via the Strasbourg Astronomical Data Center (CDS) and NED. [ABSTRACT FROM AUTHOR]

In maize vivipary, the precocious germination of the seed while it is still attached to the ear is a reliable phenotype for the identification of mutants impaired in the biosynthesis or response to abscisic acid (ABA). Here we present the characterization of a new allele of vp10, a gene encoding for a cofactor (MoCo) required for the last step of ABA biosynthesis. The lesion in this gene leads to a reduction in the endogenous ABA level. Embryonic messenger RNAs of the ABA inducible genes glb1, lea3, and rab17 are barely detectable, although their level increases when stimulated by exogenous ABA administration. These findings confirm that the mutant can be ascribed to a defect in ABA biosynthesis. In the absence of water stress, mutant plants grow like wild-type siblings; however when mutant tissues are exposed to air they differ from non-mutant ones by showing a higher rate of water loss, of transpiration and of stomatal conductance. These events are restored to almost normal values by adding exogenous ABA. All these defects are ascribable to an impairment in the regulation of stomatal opening since, in contrast to wild-type, some of the mutant stomata exhibit partially or totally open rims. The defect in ABA biosynthesis is also associated with loss of regulation of the expression of rab17 and rab28, two genes expressed in vegetative tissues under abiotic stress. These genes are constitutively expressed in the mutant plant tissues independently of the water regime applied. Thus this mutant may provide a tool for the study of molecular mechanisms underlying drought-stress responses in crop plants. [ABSTRACT FROM AUTHOR]

The maize seed comprises two major compartments, the embryo and the endosperm, both originating from the double fertilization event. The embryogenetic process allows the formation of a well-differentiated embryonic axis, surrounded by a single massive cotyledon, the scutellum. The mature endosperm constitutes the bulk of the seed and comprises specific regions containing reserve proteins, complex carbohydrates, and oils. To gain more insight into molecular events that underlie seed development, three monogenic mutants were characterized, referred to as emp (empty pericarp) on the basis of their extreme endosperm reduction, first recognizable at about 12 d after pollination. Their histological analysis reveals a partial development of the endosperm domains as well as loss of adhesion between pedicel tissues and the basal transfer layer. In the endosperm, programmed cell death (PCD) is delayed. The embryo appears retarded in its growth, but not impaired in its morphogenesis. The mutants can be rescued by culturing immature embryos, even though the seedlings appear retarded in their growth. The analysis of seeds with discordant embryo–endosperm phenotype (mutant embryo, normal endosperm and vice-versa), obtained using B–A translocations, suggests that emp expression in the embryo is necessary, but not sufficient, for proper seed development. In all three mutants the picture emerging is one of a general delay in processes related to growth, as a result of a mutation affecting endosperm development as a primary event. [ABSTRACT FROM PUBLISHER]

The pentatricopeptide repeat (PPR) family represents one of the largest gene families in plants, with >440 members annotated in Arabidopsis thaliana. PPR proteins are thought to have a major role in the regulation of posttranscriptional processes in organelles. Recent studies have shown that Arabidopsis PPR proteins play an essential, nonredundant role during embryogenesis. Here, we demonstrate that mutations in empty pericarp4 (emp4), a maize (Zea mays) PPR-encoding gene, confer a seed-lethal phenotype. Mutant endosperms are severely impaired, with highly irregular differentiation of transfer cells in the nutrient-importing basal endosperm. Analysis of homozygous mutant plants generated from embryo-rescue experiments indicated that emp4 also affects general plant growth. The emp4-1 mutation was identified in an active Mutator (Mu) population, and cosegregation analysis revealed that it arose from a Mu3 element insertion. Evidence of emp4 molecular cloning was provided by the isolation of four additional emp4 alleles obtained by a reverse genetics approach. emp4 encodes a novel type of PPR protein of 614 amino acids. EMP4 contains nine 35-amino acid PPR motifs and an N-terminal mitochondrion-targeted sequence peptide, which was confirmed by a translational EMP4-green fluorescent protein fusion that localized to mitochondria. Molecular analyses further suggest that EMP4 is necessary to regulate the correct expression of a small subset of mitochondrial transcripts in the endosperm. [ABSTRACT FROM AUTHOR]

• Background In angiosperms the seed is the outcome of double fertilization, a process leading to the formation of the embryo and the endosperm. The development of the two seed compartments goes through three main phases: polarization, differentiation of the main tissues and organs and maturation.• Scope This review focuses on the maize kernel as a model system for developmental and genetic studies of seed development in angiosperms. An overview of what is known about the genetic and molecular aspects underlying embryo and endosperm formation and maturation is presented. The role played by embryonic meristems in laying down the plant architecture is discussed. The acquisition of the different endosperm domains are presented together with the use of molecular markers available for the detection of these domains. Finally the role of programmed cell death in embryo and endosperm development is considered.• Conclusions The sequence of events occurring in the developing maize seed appears to be strictly regulated. Proper seed development requires the co-ordinated expression of embryo and endosperm genes and relies on the interaction between the two seed components and between the seed and the maternal tissues. Mutant analysis is instrumental in unravelling the genetic control underlying the formation of each compartment as well as the molecular signals interplaying between the two compartments. [ABSTRACT FROM AUTHOR]

Programmed cell death (PCD) in plants is considered an integral part of development. Evidence of DNA fragmentation, occurring at specific sites and times during embryo formation in maize (Zea mays L.), was obtained using terminal deoxyribonucleotidyl transferase‐mediated dUTP‐fluorescein nick end labelling (TUNEL) and by genomic DNA ladder detection. During the crucial period of elaboration of the primary shoot and root axis (14–20 d after pollination), TUNEL‐positive nuclei are present in the scutellum, coleoptile, root cap and principally in the suspensor. Additional evidence of a form of programmed cell death occurring in these tissues comes from the detection of a DNA ladder. Upon completion of the differentiation process, all embryonic cells are TUNEL‐negative, indicating that possible programmed cell death events during maize embryogenesis are confined to structures or organs that do not contribute to the adult plant body. [ABSTRACT FROM PUBLISHER]

We present an analysis of the kinematics and ionization conditions in a sample composed of seven star-forming galaxies undergoing ram-pressure stripping in the A1367 cluster, and the galaxy ESO137–001 in the Norma cluster. MUSE observations of two new galaxies in this sample, CGCG097–073 and CGCG097–079, are also presented. This sample is characterized by homogeneous integral field spectroscopy with MUSE and by a consistent selection based on the presence of ionized gas tails. The ratio [O  i ]/H α is consistently elevated in the tails of these objects compared to what observed in unperturbed galaxy discs, an ubiquitous feature which we attribute to shocks or turbulent phenomena in the stripped gas. Compact star-forming regions are observed in only |$\approx 50 {{\ \rm per\ cent}}$| of the tails, implying that specific (currently unknown) conditions are needed to trigger star formation inside the stripped gas. Focusing on the interface regions between the interstellar and intracluster medium, we observe different line ratios that we associate to different stages of the stripping process, with galaxies at an early stage of perturbation showing more prominent signatures of elevated star formation. Our analysis, thus, demonstrates the power of a well selected and homogeneous sample to infer general properties arising from ram-pressure stripping inside local clusters. [ABSTRACT FROM AUTHOR]

The molecular gas mass in nearby galaxies is generally estimated using 12CO(1-0) line intensities and assuming the X conversion factor between I(CO) and N(H2) measured in the solar neighborhood. It is however known that this X conversion factor is not universal since it changes with metallicity, cosmic ray density and UV radiation field. Far-IR data in the spectral range 100-1000 μm can be used to estimate the molecular gas content of late-type galaxies in an independent way of CO line measurements once a metallicity-dependent dust to gas ratio is assumed, allowing a direct estimate of X. This exercise is presented here for a large sample of galaxies with available multifrequency data. X spans from ∼ 1020 mol cm-2 (K km s-1)-1 in giant spirals to ∼ 1021 mol cm-2 (K km s-1)-1 in dwarf irregulars. [ABSTRACT FROM AUTHOR]

Abstract: Dwarf mutants have been instrumental in the elucidation of gibberellin (GA) metabolism and of their role on a wide range of plant physiological processes. Based on their response to the application of exogenous GAs, dwarf mutants have been divided into two major groups, GA-responsive and GA-insensitive mutants. Here we report on the characterization of an1-4736, a chemically (EMS) induced allele of an1 that belongs to the GA-responsive group. Striking aspects of this mutant allele are its early developmental time of response to GA3 administration and its capacity to partially repress scotomorphogenesis. When grown in continuous darkness the mutant shows traits usually associated with light-grown plants, such as leaf unfolding, reduction in seedling elongation and induction of light controlled genes. A partial impairment of mutant growth is also observed upon its transfer to light. Since other light-regulated processes appear normal in the mutant, it might be that the lesion in the GA metabolism specifically affects the light dependent signal pathway controlling plant elongation. These results, suggesting a dual role of GAs, one of promotion of stem elongation in light and a second one of repression of photomorphogenesis in darkness, are indicative of an interaction between GAs and light signals in the modulation of growth. [Copyright &y& Elsevier]

Recent studies have highlighted the potential significance of intracluster medium (ICM) clumping and its important implications for cluster cosmology and baryon physics. Many of the ICM clumps can originate from infalling galaxies, as stripped interstellar medium (ISM) mixing into the hot ICM. However, a direct connection between ICM clumping and stripped ISM has not been unambiguously established before. Here, we present the discovery of the first and still the only known isolated cloud (or orphan cloud [OC]) detected in both X-rays and H α in the nearby cluster A1367. With an effective radius of 30 kpc, this cloud has an average X-ray temperature of 1.6 keV, a bolometric X-ray luminosity of ∼3.1 × 1041 erg s−1, and a hot gas mass of ∼1010 M⊙. From the Multi-Unit Spectroscopic Explorer (MUSE) data, the OC shows an interesting velocity gradient nearly along the east-west direction with a low level of velocity dispersion of ∼80 km s−1, which may suggest a low level of the ICM turbulence. The emission line diagnostics suggest little star formation in the main H α cloud and a low-ionization (nuclear) emission-line regions like spectrum, but the excitation mechanisms remain unclear. This example shows that stripped ISM, even long after the initial removal from the galaxy, can still induce ICM inhomogeneities. We suggest that the magnetic field can stabilize the OC by suppressing hydrodynamic instabilities and thermal conduction. This example also suggests that at least some ICM clumps are multiphase in nature and implies that the ICM clumps can also be traced in H α. Thus, future deep and wide-field H α surveys can be used to probe the ICM clumping and turbulence. [ABSTRACT FROM AUTHOR]