A nuclease specific to lepidopteran insects suppresses RNAi

More than 70% of all agricultural pests are insects in the order Lepidoptera, which, unlike other related insect orders, are not very sensitive to RNAi, limiting genetic studies of this insect group. However, the reason for this distinct lepidopteran characteristic is unknown. Previously, using transcriptome analysis of the Asian corn borer Ostrinia furnacalis, we identified a gene, termed up56, that is up-regulated in response to dsRNA. Here we report that this Lepidoptera-specific gene encodes a nuclease that contributes to RNAi insensitivity in this insect order. Its identity was experimentally validated, and sequence analysis indicated that up56 encodes a previously uncharacterized protein with homologous sequences in seven other lepidopteran species. Its computationally predicted three-dimensional structure revealed a high structural similarity to human exonuclease I. Exposure to dsRNA in O. furnacalis strongly up-regulated this gene's expression, and the protein could digest single-stranded RNA (ssRNA), dsRNA, and dsDNA both in vitro and in vivo. Of note, we found that this up-regulation of up56 expression is faster than that of the gene encoding the key RNAi-associated nuclease Dicer. up56 knockdown in O. furnacalis significantly enhanced RNAi efficiency. Moreover, up56 overexpression in Drosophila melanogaster suppressed RNAi efficiency. Finally, up56 knockdown significantly increased the amount and diversity of small RNAs. Therefore, we renamed this protein RNAi efficiency-related nuclease (REase). In conclusion, we propose that REase may explain why lepidopterans are refractory to RNAi and that it represents a target for further research of RNAi efficiency in this insect order

Engineering Plateau Phase Transition in Quantum Anomalous Hall Multilayers

The plateau phase transition in quantum anomalous Hall (QAH) insulators corresponds to a quantum state wherein a single magnetic domain gives way to multiple magnetic domains and then re-converges back to a single magnetic domain. The layer structure of the sample provides an external knob for adjusting the Chern number C of the QAH insulators. Here, we employ molecular beam epitaxy (MBE) to grow magnetic topological insulator (TI) multilayers with an asymmetric layer structure and realize the magnetic field-driven plateau phase transition between two QAH states with odd Chern number change {\Delta}C. In multilayer structures with C=+-1 and C=+-2 QAH states, we find two characteristic power-law behaviors between temperature and the scaling variables on the magnetic field at transition points. The critical exponents extracted for the plateau phase transitions with {\Delta}C=1 and {\Delta}C=3 in QAH insulators are found to be nearly identical, specifically, k1~0.390+-0.021 and k2~0.388+-0.015, respectively. We construct a four-layer Chalker-Coddington network model to understand the consistent critical exponents for the plateau phase transitions with {\Delta}C=1 and {\Delta}C=3. This work will motivate further investigations into the critical behaviors of plateau phase transitions with different {\Delta}C in QAH insulators and provide new opportunities for the development of QAH chiral edge current-based electronic and spintronic devices.Comment: 18 pages, 4 figures. Comments are welcom

Probing Primordial Gravitational Waves: Ali CMB Polarization Telescope

In this paper, we will give a general introduction to the project of Ali CMB Polarization Telescope (AliCPT), which is a Sino-US joint project led by the Institute of High Energy Physics (IHEP) and has involved many different institutes in China. It is the first ground-based Cosmic Microwave Background (CMB) polarization experiment in China and an integral part of China's Gravitational Waves Program. The main scientific goal of AliCPT project is to probe the primordial gravitational waves (PGWs) originated from the very early Universe. The AliCPT project includes two stages. The first stage referred to as AliCPT-1, is to build a telescope in the Ali region of Tibet with an altitude of 5,250 meters. Once completed, it will be the worldwide highest ground-based CMB observatory and open a new window for probing PGWs in northern hemisphere. AliCPT-1 telescope is designed to have about 7,000 TES detectors at 90GHz and 150GHz. The second stage is to have a more sensitive telescope (AliCPT-2) with the number of detectors more than 20,000. Our simulations show that AliCPT will improve the current constraint on the tensor-to-scalar ratio $r$ by one order of magnitude with 3 years' observation. Besides the PGWs, the AliCPT will also enable a precise measurement on the CMB rotation angle and provide a precise test on the CPT symmetry. We show 3 years' observation will improve the current limit by two order of magnitude.Comment: 11 pages, 7 figures, 2 table