The caterpillar fungus Ophiocordyceps sinensis (best known as Cordyceps sinensis) mummifies ghost moth larvae exclusively in Tibetan Plateau alpine ecosystems. Touted as "Himalayan Viagra", the fungus is highly prized due to its medical benefits and dwindling supplies. Attempts to culture the sexual fruiting-body have failed and the huge market demand has led to severe devastation of local ecosystems and to the fungus heading towards extinction. By genome sequencing, we establish that unlike related insect pathogens O. sinensis contains two compatible mating-type genes in its genome and is self-fertile, i.e. homothallic. However, sexual processes are only initiated under native environmental conditions. O. sinensis resembles biotrophic plant pathogens in having a genome shaped by retrotransposon-driven expansions. The resulting changes in gene content suggest that O. sinensis has a biphasic pathogenic mechanism beginning with stealth pathogenesis in early host instars. O. sinensis is the first psychrophilic fungus sequenced and is adapted to extreme cold with putative antifreeze proteins and mechanisms for increasing lipid accumulation and fatty acid unsaturation. We hypothesize that for the inbreeding O. sinensis the massive proliferation of retrotransposons provides a tradeoff between the advantages of increased genetic variation independent of sexual recombination and deletion of genes dispensable for its specialized pathogenic lifestyle.Ophiocordyceps sinensis, genome expansion, homothallism, biotrophic parasitism, psychrophile
Citation:Hu X, Zhang Y J, Xiao G H, et al. Genome survey uncovers the secrets of sex and lifestyle in caterpillar fungus.
As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the
The Insight-Hard X-ray Modulation Telescope (Insight-HXMT) is a broad band X-ray and gamma-ray (1-3000 keV) astronomy satellite. The High Energy X-ray telescope (HE) is one of its three main telescopes. The main detector plane of HE is composed of 18 NaI(Tl)/CsI(Na) phoswich detectors, where NaI(Tl) serves as primary detector to measure ~ 20-250 keV photons incident from the field of view (FOV) defined by the collimators, and CsI(Na) is used as an active shield detector to NaI(Tl) by pulse shape discrimination. CsI(Na) is also used as an omnidirectional gamma-ray monitor. The HE collimators have a diverse FOV: 1.1°x 5.7° (15 units), 5.7°x 5.7° (2 units) and blocked (1 unit), thus the combined FOV of HE is about 5.7°x 5.7°. Each HE detector has a diameter of 190 mm, resulting in the total geometrical area of about 5100 cm 2 . The energy resolution is ~15% at 60 keV. The timing accuracy is better than 10 μs and dead-time for each detector is less than 10 μs. HE is devoted to observe the spectra and temporal variability of X-ray sources in the 20-250 keV band either by pointing observations for known sources or scanning observations to unveil new sources, and to monitor the gamma-ray sky in 0.2-3 MeV. This paper presents the design and performance of the HE instruments. Results of the on-ground calibration experiments are also reported.
The Medium Energy X-ray telescope (ME) is one of the three main telescopes on board the Insight hard X-ray modulation telescope (Insight-HXMT) astronomy satellite. ME contains 1728 pixels of Si-PIN detectors sensitive in 5-30 keV with a total geometrical area of 952 cm 2 . The application specific integrated circuit (ASIC) chip, VA32TA6, is used to achieve low power consumption and low readout noise. The collimators define three kinds of field of views (FOVs) for the telescope, 1°×4°, 4°×4°, and blocked ones. Combination of such FOVs can be used to estimate the in-orbit X-ray and particle background components. The energy resolution of ME is~3 keV at 17.8 keV (FWHM) and the time resolution is 255 μs. In this paper, we introduce the design and performance of ME.
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