Alfvén Waves in the Lower Solar Atmosphere

The flow of energy through the solar atmosphere and the heating of the Sun's outer regions are still not understood. Here, we report the detection of oscillatory phenomena associated with a large bright-point group that is 430,000 square kilometers in area and located near the solar disk center. Wavelet analysis reveals full-width half-maximum oscillations with periodicities ranging from 126 to 700 seconds originating above the bright point and significance levels exceeding 99%. These oscillations, 2.6 kilometers per second in amplitude, are coupled with chromospheric line-of-sight Doppler velocities with an average blue shift of 23 kilometers per second. A lack of cospatial intensity oscillations and transversal displacements rules out the presence of magneto-acoustic wave modes. The oscillations are a signature of Alfvén waves produced by a torsional twist of ±22 degrees. A phase shift of 180 degrees across the diameter of the bright point suggests that these torsional Alfvén oscillations are induced globally throughout the entire brightening. The energy flux associated with this wave mode is sufficient to heat the solar corona.

Aligning conservation priorities across taxa in Madagascar with high-resolution planning tools

Globally, priority areas for biodiversity are relatively well known, yet few detailed plans exist to direct conservation action within them, despite urgent need. Madagascar, like other globally recognized biodiversity hot spots, has complex spatial patterns of endemism that differ among taxonomic groups, creating challenges for the selection of within-country priorities. We show, in an analysis of wide taxonomic and geographic breadth and high spatial resolution, that multitaxonomic rather than single-taxon approaches are critical for identifying areas likely to promote the persistence of most species. Our conservation prioritization, facilitated by newly available techniques, identifies optimal expansion sites for the Madagascar government's current goal of tripling the land area under protection. Our findings further suggest that high-resolution multitaxonomic approaches to prioritization may be necessary to ensure protection for biodiversity in other global hot spots.

The Disappearance of the Progenitors of Supernovae 1993J and 2003gd

Using images from the Hubble Space Telescope and the Gemini Telescope, we confirmed the disappearance of the progenitors of two type II supernovae (SNe) and evaluated the presence of other stars associated with them. We found that the progenitor of SN 2003gd, an M-supergiant star, is no longer observed at the SN location and determined its intrinsic brightness using image subtraction techniques. The progenitor of SN 1993J, a K-supergiant star, is also no longer present, but its B-supergiant binary companion is still observed. The disappearance of the progenitors confirms that these two supernovae were produced by red supergiants.

Targeted 3' processing of antisense transcripts triggers Arabidopsis FLC chromatin silencing.

Noncoding RNA is emerging as an important regulator of gene expression in many organisms. We are characterizing RNA-mediated chromatin silencing of the Arabidopsis major floral repressor gene, FLC. Through suppressor mutagenesis, we identify a requirement for CstF64 and CstF77, two conserved RNA 3'-end-processing factors, in FLC silencing. However, FLC sense transcript 3' processing is not affected in the mutants. Instead, CstF64 and CstF77 are required for 3' processing of FLC antisense transcripts. A specific RNA-binding protein directs their activity to a proximal antisense polyadenylation site. This targeted processing triggers localized histone demethylase activity and results in reduced FLC sense transcription. Targeted 3' processing of antisense transcripts may be a common mechanism triggering transcriptional silencing of the corresponding sense gene.

PI3K beta Plays a Critical Role in Neutrophil Activation by Immune Complexes

Neutrophils are activated by immunoglobulin G (IgG)-containing immune complexes through receptors that recognize the Fc portion of IgG (Fc gamma Rs). Here, we used genetic and pharmacological approaches to define a selective role for the beta isoform of phosphoinositide 3-kinase (PI3K beta) in Fc gamma R-dependent activation of mouse neutrophils by immune complexes of IgG and antigen immobilized on a plate surface. At low concentrations of immune complexes, loss of PI3K beta alone substantially inhibited the production of reactive oxygen species (ROS) by neutrophils, whereas at higher doses, similar suppression of ROS production was achieved only by targeting both PI3K beta and PI3K delta, suggesting that this pathway displays stimulus strength-dependent redundancy. Activation of PI3K beta by immune complexes involved cooperation between Fc gamma Rs and BLT1, the receptor for the endogenous proinflammatory lipid leukotriene B-4. Coincident activation by a tyrosine kinase-coupled receptor (Fc gamma R) and a heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor (BLT1) may provide a rationale for the preferential activation of the beta isoform of PI3K. PI3K beta-deficient mice were highly protected in an Fc gamma R-dependent model of autoantibody-induced skin blistering and were partially protected in an Fc gamma R-dependent model of inflammatory arthritis, whereas combined deficiency of PI3K beta and PI3K delta resulted in near-complete protection in the latter case. These results define PI3K beta as a potential therapeutic target in inflammatory disease.

How and why do insects migrate?

Countless numbers of insects migrate within and between continents every year, and yet we know very little about the ultimate reasons and proximate mechanisms that would explain these mass movements. Here we suggest that perhaps the most important reason for insects to migrate is to hedge their reproductive bets. By spreading their breeding efforts in space and time, insects distribute their offspring over a range of environmental conditions. We show how the study of individual long-distance movements of insects may contribute to a better understanding of migration. In the future, advances in tracking methods may enable the global surveillance of large insects such as desert locusts.

Glacial Survival of Boreal Trees in Northern Scandinavia

It is commonly believed that trees were absent in Scandinavia during the last glaciation and first recolonized the Scandinavian Peninsula with the retreat of its ice sheet some 9000 years ago. Here, we show the presence of a rare mitochondrial DNA haplotype of spruce that appears unique to Scandinavia and with its highest frequency to the west—an area believed to sustain ice-free refugia during most of the last ice age. We further show the survival of DNA from this haplotype in lake sediments and pollen of Trøndelag in central Norway dating back ~10,300 years and chloroplast DNA of pine and spruce in lake sediments adjacent to the ice-free Andøya refugium in northwestern Norway as early as ~22,000 and 17,700 years ago, respectively. Our findings imply that conifer trees survived in ice-free refugia of Scandinavia during the last glaciation, challenging current views on survival and spread of trees as a response to climate changes.

Cotranscriptional role for Arabidopsis DICER-LIKE 4 in transcription termination.

Transcription termination is emerging as an important component of gene regulation necessary to partition the genome and minimize transcriptional interference. We have discovered a role for the Arabidopsis RNA silencing enzyme DICER-LIKE 4 (DCL4) in transcription termination of an endogenous Arabidopsis gene, FCA. DCL4 directly associates with FCA chromatin in the 3' region and promotes cleavage of the nascent transcript in a domain downstream of the canonical polyA site. In a dcl4 mutant, the resulting transcriptional read-through triggers an RNA interference–mediated gene silencing of a transgene containing the same 3' region. We conclude that DCL4 promotes transcription termination of the Arabidopsis FCA gene, reducing the amount of aberrant RNA produced from the locus.

The metamorphosis of supernova SN 2008D/XRF 080109: A link between supernovae and GRBs/hypernovae

The only supernovae (SNe) to show gamma-ray bursts ( GRBs) or early x-ray emission thus far are overenergetic, broad- lined type Ic SNe ( hypernovae, HNe). Recently, SN 2008D has shown several unusual features: (i) weak x-ray flash (XRF), (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SN Ic HNe, and (iv) development of helium lines as in SNe Ib. Detailed analysis shows that SN 2008D was not a normal supernova: Its explosion energy (E approximate to 6 x 10(51) erg) and ejected mass [similar to 7 times the mass of the Sun ( M.)] are intermediate between normal SNe Ibc and HNe. We conclude that SN 2008D was originally a similar to 30 M. star. When it collapsed, a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.

Response to Comment on "Glacial Survival of Boreal Trees in Northern Scandinavia"

Birks et al. question our proposition that trees survived the Last Glacial Maximum (LGM) in Northern Scandinavia. We dispute their interpretation of our modern genetic data but agree that more work is required. Our field and laboratory procedures were robust; contamination is an unlikely explanation of our results. Their description of Endletvatn as ice-covered and inundated during the LGM is inconsistent with recent geological literature.

Lung Microbiota and Bacterial Abundance in Patients with Bronchiectasis when Clinically Stable and during Exacerbation

RATIONALE: Characterization of bacterial populations in infectious respiratory diseases will provide improved understanding of the relationship between the lung microbiota, disease pathogenesis and treatment outcomes.

OBJECTIVES: To comprehensively define lung microbiota composition during stable disease and exacerbation in bronchiectasis patients.

METHODS: Sputum was collected from patients when clinically stable and before and after completion of antibiotic treatment of exacerbations. Bacterial abundance and community composition were analyzed using anaerobic culture and 16S rDNA pyrosequencing.

MEASUREMENTS AND MAIN RESULTS: In clinically stable patients, aerobic and anaerobic bacteria were detected in 40/40 (100%) and 33/40 (83%) sputum samples, respectively. The dominant organisms cultured were P. aeruginosa (n=10 patients), H. influenzae (n=12), Prevotella (n=18) and Veillonella (n=13). Pyrosequencing generated over 150,000 sequences, representing 113 distinct microbial taxa; the majority of observed community richness resulted from taxa present in low abundance with similar patterns of phyla distribution in clinically stable patients and patients at the onset of exacerbation. Following treatment of exacerbation, there was no change in total (p=0.925), aerobic (p=0.917) or anaerobic (p=0.683) load and only a limited shift in community composition. Agreement for detection of bacteria by culture and pyrosequencing was good for aerobic bacteria such as P. aeruginosa (kappa=0.84) but poorer for other genera including anaerobes. Lack of agreement was largely due to bacteria been detected by pyrosequencing but not by culture.

CONCLUSIONS: A complex microbiota is present in the lungs of bronchiectasis patients which remains stable through treatment of exacerbations suggesting that changes in microbiota composition do not account for exacerbations.