546 research outputs found
Onset of virus systemic infection in plants is determined by speed of cell-to-cell movement and number of primary infection foci
The cornerstone of today's plant virology consists of deciphering the molecular and mechanistic basis of host-pathogen interactions. Among these interactions, the onset of systemic infection is a fundamental variable in studying both within-and between-host infection dynamics, with implications in epidemiology. Here, we developed a mechanistic model using probabilistic and spatio-temporal concepts to explain dynamic signatures of virus systemic infection. The model dealt with the inherent characteristic of plant viruses to use two different and sequential stages for their within-host propagation: cell-to-cell movement from the initial infected cell and systemic spread by reaching the vascular system. We identified the speed of cell-to-cell movement and the number of primary infection foci in the inoculated leaf as the key factors governing this dynamic process. Our results allowed us to quantitatively understand the timing of the onset of systemic infection, describing this global process as a consequence of local spread of viral populations. Finally, we considered the significance of our predictions for the evolution of plant RNA viruses.This work was supported by the grant no. BFU2012-30805 from Spain Ministerio de Economia y Competitividad (MINECO) to S. F. E. G. R. was supported by an EMBO long-term fellowship co-funded by Marie Curie actions (ALTF-1177-2011) and an AXA post-doctoral fellowship, and M.P.Z. by a Juan de la Cierva post-doctoral contract (JCI-2011-10379) from MINECO.Rodrigo Tarrega, G.; Zwart, MP.; Elena Fito, SF. (2014). Onset of virus systemic infection in plants is determined by speed of cell-to-cell movement and number of primary infection foci. Interface. 11(98):1-8. https://doi.org/10.1098/rsif.2014.0555S181198Waigmann, E., Ueki, S., Trutnyeva, K., & Citovsky, V. (2004). The Ins and Outs of Nondestructive Cell-to-Cell and Systemic Movement of Plant Viruses. Critical Reviews in Plant Sciences, 23(3), 195-250. doi:10.1080/07352680490452807Waterhouse, P. M., Wang, M.-B., & Lough, T. (2001). Gene silencing as an adaptive defence against viruses. Nature, 411(6839), 834-842. doi:10.1038/35081168Dunoyer, P., Lecellier, C.-H., Parizotto, E. A., Himber, C., & Voinnet, O. (2004). RETRACTED: Probing the MicroRNA and Small Interfering RNA Pathways with Virus-Encoded Suppressors of RNA Silencing. The Plant Cell, 16(5), 1235-1250. doi:10.1105/tpc.020719Kermack, W. O., & McKendrick, A. G. (1927). A Contribution to the Mathematical Theory of Epidemics. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 115(772), 700-721. doi:10.1098/rspa.1927.0118Segarra, J., Jeger, M. J., & van den Bosch, F. (2001). Epidemic Dynamics and Patterns of Plant Diseases. Phytopathology, 91(10), 1001-1010. doi:10.1094/phyto.2001.91.10.1001Keeling, M. (2005). The implications of network structure for epidemic dynamics. Theoretical Population Biology, 67(1), 1-8. doi:10.1016/j.tpb.2004.08.002Dolja, V. V., McBride, H. J., & Carrington, J. C. (1992). Tagging of plant potyvirus replication and movement by insertion of beta-glucuronidase into the viral polyprotein. Proceedings of the National Academy of Sciences, 89(21), 10208-10212. doi:10.1073/pnas.89.21.10208Zwart, M. P., Daròs, J.-A., & Elena, S. F. (2011). One Is Enough: In Vivo Effective Population Size Is Dose-Dependent for a Plant RNA Virus. PLoS Pathogens, 7(7), e1002122. doi:10.1371/journal.ppat.1002122Bedoya, L. C., Martínez, F., Orzáez, D., & Daròs, J.-A. (2012). Visual Tracking of Plant Virus Infection and Movement Using a Reporter MYB Transcription Factor That Activates Anthocyanin Biosynthesis. Plant Physiology, 158(3), 1130-1138. doi:10.1104/pp.111.192922Lafforgue, G., Tromas, N., Elena, S. F., & Zwart, M. P. (2012). Dynamics of the Establishment of Systemic Potyvirus Infection: Independent yet Cumulative Action of Primary Infection Sites. Journal of Virology, 86(23), 12912-12922. doi:10.1128/jvi.02207-12Holmes, F. O. (1929). Local Lesions in Tobacco Mosaic. Botanical Gazette, 87(1), 39-55. doi:10.1086/333923BALD, J. G. (1937). THE USE OF NUMBERS OF INFECTIONS FOR COMPARING THE CONCENTRATION OF PLANT VIRUS SUSPENSIONS: DILUTION EXPERIMENTS WITH PURIFIED SUSPENSIONS. Annals of Applied Biology, 24(1), 33-55. doi:10.1111/j.1744-7348.1937.tb05019.xBaulcombe, D. (2004). RNA silencing in plants. Nature, 431(7006), 356-363. doi:10.1038/nature02874Kunkel, B. N., & Brooks, D. M. (2002). Cross talk between signaling pathways in pathogen defense. Current Opinion in Plant Biology, 5(4), 325-331. doi:10.1016/s1369-5266(02)00275-3Kørner, C. J., Klauser, D., Niehl, A., Domínguez-Ferreras, A., Chinchilla, D., Boller, T., … Hann, D. R. (2013). The Immunity Regulator BAK1 Contributes to Resistance Against Diverse RNA Viruses. Molecular Plant-Microbe Interactions, 26(11), 1271-1280. doi:10.1094/mpmi-06-13-0179-rRodrigo, G., Carrera, J., Jaramillo, A., & Elena, S. F. (2010). Optimal viral strategies for bypassing RNA silencing. Journal of The Royal Society Interface, 8(55), 257-268. doi:10.1098/rsif.2010.0264Kleczkowski, A. (1950). Interpreting Relationships between the Concentrations of Plant Viruses and Numbers of Local Lesions. Journal of General Microbiology, 4(1), 53-69. doi:10.1099/00221287-4-1-53Van der Plank, J. E. (1965). Dynamics of Epidemics of Plant Disease: Population bursts of fungi, bacteria, or viruses in field and forest make an interesting dynamical study. Science, 147(3654), 120-124. doi:10.1126/science.147.3654.120Zwart, M. P., Daròs, J.-A., & Elena, S. F. (2012). Effects of Potyvirus Effective Population Size in Inoculated Leaves on Viral Accumulation and the Onset of Symptoms. Journal of Virology, 86(18), 9737-9747. doi:10.1128/jvi.00909-12Carrington, J. C., Kasschau, K. D., Mahajan, S. K., & Schaad, M. C. (1996). Cell-to-Cell and Long-Distance Transport of Viruses in Plants. The Plant Cell, 1669-1681. doi:10.1105/tpc.8.10.1669Gibbs, A. (1976). Viruses and Plasmodesmata. Intercellular Communication in Plants: Studies on Plasmodesmata, 149-164. doi:10.1007/978-3-642-66294-2_8Hillung, J., Elena, S. F., & Cuevas, J. M. (2013). Intra-specific variability and biological relevance of P3N-PIPO protein length in potyviruses. BMC Evolutionary Biology, 13(1), 249. doi:10.1186/1471-2148-13-249Dengler, N., & Kang, J. (2001). Vascular patterning and leaf shape. Current Opinion in Plant Biology, 4(1), 50-56. doi:10.1016/s1369-5266(00)00135-7SAMUEL, G. (1934). The Movement of Tobacco Mosaic Virus Within the Plant. Annals of Applied Biology, 21(1), 90-111. doi:10.1111/j.1744-7348.1934.tb06891.xKawakami, S., Watanabe, Y., & Beachy, R. N. (2004). Tobacco mosaic virus infection spreads cell to cell as intact replication complexes. Proceedings of the National Academy of Sciences, 101(16), 6291-6296. doi:10.1073/pnas.0401221101Bedoya, L., Martínez, F., Rubio, L., & Daròs, J.-A. (2010). Simultaneous equimolar expression of multiple proteins in plants from a disarmed potyvirus vector. Journal of Biotechnology, 150(2), 268-275. doi:10.1016/j.jbiotec.2010.08.006Wei, T., Zhang, C., Hong, J., Xiong, R., Kasschau, K. D., Zhou, X., … Wang, A. (2010). Formation of Complexes at Plasmodesmata for Potyvirus Intercellular Movement Is Mediated by the Viral Protein P3N-PIPO. PLoS Pathogens, 6(6), e1000962. doi:10.1371/journal.ppat.1000962Bragard, C., Caciagli, P., Lemaire, O., Lopez-Moya, J. J., MacFarlane, S., Peters, D., … Torrance, L. (2013). Status and Prospects of Plant Virus Control Through Interference with Vector Transmission. 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Possible chiral phase transition in two-dimensional solid He
We study a spin system with two- and four-spin exchange interactions on the
triangular lattice, which is a possible model for the nuclear magnetism of
solid He layers. It is found that a novel spin structure with scalar chiral
order appears if the four-spin interaction is dominant. Ground-state properties
are studied using the spin-wave approximation. A phase transition concerning
the scalar chirality occurs at a finite temperature, even though the
dimensionality of the system is two and the interaction has isotropic spin
symmetry. Critical properties of this transition are studied with Monte Carlo
simulations in the classical limit.Comment: 4 pages, Revtex, 4 figures, to appear in Phys.Rev.Let
Environmental pressure from the 2014–15 eruption of Bárðarbunga volcano, Iceland
The effusive six months long 2014-2015 Bárðarbunga eruption (31 August-27 February) was the largest in Iceland for more than 200 years, producing 1.6 ± 0.3 km3 of lava. The total SO2 emission was 11 ± 5 Mt, more than the amount emitted from Europe in 2011. The ground level concentration of SO2 exceeded the 350 μg m−3 hourly average health limit over much of Iceland for days to weeks. Anomalously high SO2 concentrations were also measured at several locations in Europe in September. The lowest pH of fresh snowmelt at the eruption site was 3.3, and 3.2 in precipitation 105 km away from the source. Elevated dissolved H2SO4, HCl, HF, and metal concentrations were measured in snow and precipitation. Environmental pressures from the eruption and impacts on populated areas were reduced by its remoteness, timing, and the weather. The anticipated primary environmental pressure is on the surface
waters, soils, and vegetation of Iceland
Water in low-mass star-forming regions with Herschel: HIFI spectroscopy of NGC1333
'Water In Star-forming regions with Herschel' (WISH) is a key programme
dedicated to studying the role of water and related species during the
star-formation process and constraining the physical and chemical properties of
young stellar objects. The Heterodyne Instrument for the Far-Infrared (HIFI) on
the Herschel Space Observatory observed three deeply embedded protostars in the
low-mass star-forming region NGC1333 in several H2-16O, H2-18O, and CO
transitions. Line profiles are resolved for five H16O transitions in each
source, revealing them to be surprisingly complex. The line profiles are
decomposed into broad (>20 km/s), medium-broad (~5-10 km/s), and narrow (<5
km/s) components. The H2-18O emission is only detected in broad 1_10-1_01 lines
(>20 km/s), indicating that its physical origin is the same as for the broad
H2-16O component. In one of the sources, IRAS4A, an inverse P Cygni profile is
observed, a clear sign of infall in the envelope. From the line profiles alone,
it is clear that the bulk of emission arises from shocks, both on small (<1000
AU) and large scales along the outflow cavity walls (~10 000 AU). The H2O line
profiles are compared to CO line profiles to constrain the H2O abundance as a
function of velocity within these shocked regions. The H2O/CO abundance ratios
are measured to be in the range of ~0.1-1, corresponding to H2O abundances of
~10-5-10-4 with respect to H2. Approximately 5-10% of the gas is hot enough for
all oxygen to be driven into water in warm post-shock gas, mostly at high
velocities.Comment: Accepted for publication in the A&A HIFI special issu
HERSCHEL-HIFI spectroscopy of the intermediate mass protostar NGC7129 FIRS 2
HERSCHEL-HIFI observations of water from the intermediate mass protostar
NGC7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this
star formation environment. Six spectral settings, covering four H216O and two
H218O lines, were observed and all but one H218O line were detected. The four
H2 16 O lines discussed here share a similar morphology: a narrower, \approx 6
km/s, component centered slightly redward of the systemic velocity of NGC7129
FIRS 2 and a much broader, \approx 25 km/s component centered blueward and
likely associated with powerful outflows. The narrower components are
consistent with emission from water arising in the envelope around the
intermediate mass protostar, and the abundance of H2O is constrained to \approx
10-7 for the outer envelope. Additionally, the presence of a narrow
self-absorption component for the lowest energy lines is likely due to
self-absorption from colder water in the outer envelope. The broader component,
where the H2O/CO relative abundance is found to be \approx 0.2, appears to be
tracing the same energetic region that produces strong CO emission at high J.Comment: 6 pages, 4 figures, accepted by A&
Sensitive limits on the abundance of cold water vapor in the DM Tau protoplanetary disk
We performed a sensitive search for the ground-state emission lines of ortho-
and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI
instrument. No strong lines are detected down to 3sigma levels in 0.5 km/s
channels of 4.2 mK for the 1_{10}--1_{01} line and 12.6 mK for the
1_{11}--0_{00} line. We report a very tentative detection, however, of the
1_{10}--1_{01} line in the Wide Band Spectrometer, with a strength of
T_{mb}=2.7 mK, a width of 5.6 km/s and an integrated intensity of 16.0 mK km/s.
The latter constitutes a 6sigma detection. Regardless of the reality of this
tentative detection, model calculations indicate that our sensitive limits on
the line strengths preclude efficient desorption of water in the UV illuminated
regions of the disk. We hypothesize that more than 95-99% of the water ice is
locked up in coagulated grains that have settled to the midplane.Comment: 5 pages, 3 figures. Accepted for publication in the Herschel HIFI
special issue of A&
Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system
Context: Hydrides of the most abundant heavier elements are fundamental
molecules in cosmic chemistry. Some of them trace gas irradiated by UV or
X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a
prototypical region of high-mass star formation. Methods: W3 IRS5 was observed
by HIFI on the Herschel Space Observatory with deep integration (about 2500 s)
in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and
the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines
are found mostly in absorption, but also appear to exhibit weak emission
(P-Cyg-like). Emission requires high density, thus originates most likely near
the protostar. This is corroborated by the absence of line shifts relative to
the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong
absorption components at a velocity shifted relative to W3 IRS5, which are
attributed to foreground clouds. Conclusions: The molecular column densities
derived from observations correlate well with the predictions of a model that
assumes the main emission region is in outflow walls, heated and irradiated by
protostellar UV radiation.Comment: Astronomy and Astrophysics Letters, in pres
Water in massive star-forming regions: HIFI observations of W3 IRS5
We present Herschel observations of the water molecule in the massive
star-forming region W3 IRS5. The o-H17O 110-101, p-H18O 111-000, p-H2O 22
202-111, p-H2O 111-000, o-H2O 221-212, and o-H2O 212-101 lines, covering a
frequency range from 552 up to 1669 GHz, have been detected at high spectral
resolution with HIFI. The water lines in W3 IRS5 show well-defined
high-velocity wings that indicate a clear contribution by outflows. Moreover,
the systematically blue-shifted absorption in the H2O lines suggests expansion,
presumably driven by the outflow. No infall signatures are detected. The p-H2O
111-000 and o-H2O 212-101 lines show absorption from the cold material (T ~ 10
K) in which the high-mass protostellar envelope is embedded. One-dimensional
radiative transfer models are used to estimate water abundances and to further
study the kinematics of the region. We show that the emission in the rare
isotopologues comes directly from the inner parts of the envelope (T > 100 K)
where water ices in the dust mantles evaporate and the gas-phase abundance
increases. The resulting jump in the water abundance (with a constant inner
abundance of 10^{-4}) is needed to reproduce the o-H17O 110-101 and p-H18O
111-000 spectra in our models. We estimate water abundances of 10^{-8} to
10^{-9} in the outer parts of the envelope (T < 100 K). The possibility of two
protostellar objects contributing to the emission is discussed.Comment: Accepted for publication in the A&A HIFI special issu
Water in Star-Forming Regions with the Herschel Space Observatory (WISH): Overview of key program and first results
`Water In Star-forming regions with Herschel' (WISH) is a key program on the
Herschel Space Observatory designed to probe the physical and chemical
structure of young stellar objects using water and related molecules and to
follow the water abundance from collapsing clouds to planet-forming disks.
About 80 sources are targeted covering a wide range of luminosities and
evolutionary stages, from cold pre-stellar cores to warm protostellar envelopes
and outflows to disks around young stars. Both the HIFI and PACS instruments
are used to observe a variety of lines of H2O, H218O and chemically related
species. An overview of the scientific motivation and observational strategy of
the program is given together with the modeling approach and analysis tools
that have been developed. Initial science results are presented. These include
a lack of water in cold gas at abundances that are lower than most predictions,
strong water emission from shocks in protostellar environments, the importance
of UV radiation in heating the gas along outflow walls across the full range of
luminosities, and surprisingly widespread detection of the chemically related
hydrides OH+ and H2O+ in outflows and foreground gas. Quantitative estimates of
the energy budget indicate that H2O is generally not the dominant coolant in
the warm dense gas associated with protostars. Very deep limits on the cold
gaseous water reservoir in the outer regions of protoplanetary disks are
obtained which have profound implications for our understanding of grain growth
and mixing in disks.Comment: 71 pages, 10 figures, PASP, in pres
Herschel-HIFI detections of hydrides towards AFGL 2591 (Envelope emission versus tenuous cloud absorption)
The Heterodyne Instrument for the Far Infrared (HIFI) onboard the Herschel
Space Observatory allows the first observations of light diatomic molecules at
high spectral resolution and in multiple transitions. Here, we report deep
integrations using HIFI in different lines of hydrides towards the high-mass
star forming region AFGL 2591. Detected are CH, CH+, NH, OH+, H2O+, while NH+
and SH+ have not been detected. All molecules except for CH and CH+ are seen in
absorption with low excitation temperatures and at velocities different from
the systemic velocity of the protostellar envelope. Surprisingly, the CH(JF,P =
3/2_2,- - 1/2_1,+) and CH+(J = 1 - 0, J = 2 - 1) lines are detected in emission
at the systemic velocity. We can assign the absorption features to a foreground
cloud and an outflow lobe, while the CH and CH+ emission stems from the
envelope. The observed abundance and excitation of CH and CH+ can be explained
in the scenario of FUV irradiated outflow walls, where a cavity etched out by
the outflow allows protostellar FUV photons to irradiate and heat the envelope
at larger distances driving the chemical reactions that produce these
molecules.Comment: Accepted for publication in Astronomy and Astrophysics (HIFI first
results issue
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