RNase D Is Involved in 5S rRNA Degradation and Exopolysaccharide Production in Xanthomonas campestris pv. campestris.

Ribonucleases (RNases) play critical roles in RNA metabolism and are collectively essential for cell viability. However, most knowledge about bacterial RNases comes from the studies on Escherichia coli; very little is known about the RNases in plant pathogens. The crucifer black rot pathogen Xanthomonas campestris pv. campestris (Xcc) encodes 15 RNases, but none of them has been functionally characterized. Here, we report the physiological function of the exoribonuclease RNase D in Xcc and provide evidence demonstrating that the Xcc RNase D is involved in 5S rRNA degradation and exopolysaccharide (EPS) production. Our work shows that the growth and virulence of Xcc were not affected by deletion of RNase D but were severely attenuated by RNase D overexpression. However, deletion of RNase D in Xcc resulted in a significant reduction in EPS production. In addition, either deletion or overexpression of RNase D in Xcc did not influence the tRNAs tested, inconsistent with the finding in E. coli that the primary function of RNase D is to participate in tRNA maturation and its overexpression degrades tRNAs. More importantly, deletion, overexpression, and in vitro enzymatic analyses revealed that the Xcc RNase D degrades 5S rRNA but not 16S and 23S rRNAs that share an operon with 5S rRNA. Our results suggest that Xcc employs RNase D to realize specific modulation of the cellular 5S rRNA content after transcription and maturation whenever necessary. The finding expands our knowledge about the function of RNase D in bacteria.

Evaluation of anti-tick efficiency in rabbits induced by DNA vaccines encoding Haemaphysalis longicornis lipocalin homologue.

Haemaphysalis longicornis is an obligate haematophagous ectoparasite, transmitting a variety of pathogens, which brings great damage to human health and animal husbandry development. Lipocalins (LIP) are a family of proteins that transport small hydrophobic molecules and also involve in immune regulation, such as the regulation of cell homeostasis, inhibiting the host's inflammatory response and resisting the contractile responses in host blood vessels. Therefore, it is one of the candidate antigens for vaccines. Based on previous studies, we constructed the recombinant plasmid pcDNA3.1-HlLIP of LIP homologue from H. longicornis (HlLIP). ELISA results showed that rabbits immunized with pcDNA3.1-HlLIP produced higher anti-rHlLIP antibody levels compared with the pcDNA3.1 group, indicating that pcDNA3.1-HlLIP induced the humoral immune response of host. Adult H. longicornis infestation trial in rabbits demonstrated that the engorgement weight, oviposition and hatchability of H. longicornis fed on rabbits immunized with pcDNA3.1-HlLIP decreased by 7.07%, 14.30% and 11.70% respectively, compared with that of the pcDNA3.1 group. In brief, DNA vaccine of pcDNA3.1-HlLIP provided immune protection efficiency of 30% in rabbits. This study demonstrated that pcDNA3.1-HlLIP can partially protect rabbits against H. longicornis, and it is possible to develop a new candidate antigen against ticks.

Electric split-ring metamaterial based microfluidic chip with multi-resonances for microparticle trapping and chemical sensing applications.

In this work, an integration of terahertz (THz) electrical split-ring metamaterial (eSRM) with microfluidic chip is presented. This eSRM-based microfluidic chip exhibits multiple resonances in the THz spectrum and trapping selectively microparticle size characteristics. The arrangement of eSRM array is dislocation. It generates the fundamental inductive-capacitive (LC) resonant mode, quadrupole, and octupolar plasmon resonant modes and then exhibits high sensitivity to the environmental refraction index. The trapping structures of microparticles are elliptical barricades on eSRM surface. Thus, the electric field energy is strongly confined within the gap of eSRM in transverse electric (TE) mode and then the elliptical trapping structures are anchored on both sides of the split gap to ensure the microparticles can be trapped and located on the gap. To imitate the microparticle sensing ambient environment qualitatively and quantitatively in the THz spectrum, the microparticles are designed different feature sizes with different refraction index from 1.0 to 2.0 in ethanol medium. The results show the proposed eSRM-based microfluidic chip possesses the trapping and sensing abilities in single microparticle and high sensitivity for fungus, microorganism, chemical and environmental applications.

A voltage-controllable VO2 based metamaterial perfect absorber for CO2 gas sensing application.

Vanadium dioxide (VO2) based metamaterial perfect absorbers (MPAs) have high potential application values in sensing gas molecules. However, a tuning mechanism via temperature manipulation lacks the compatibility with electronic devices. In this study, a voltage-controllable device is proposed by integrating an MPA and micro-electro-mechanical system (MEMS) based microheater for CO2 gas sensing application. The MPA is composed of a metal-dielectric-metal (MDM) structure and tailored to form an H-shaped metamaterial. The central bar of the H-shaped metamaterial is composed of a VO2 material, which exhibits perfect absorption in the CO2 gas absorption spectrum, i.e., at a wavelength of 2.70 µm. The intergated microheater is patterned by using fractal theory to provide high heating temperature and high uniformity of surface temperature. By precisely driving a DC bias voltage on the microheater, the MPA is heated and it can exhibit switchable optical properties with high efficiency. These results provide a strategy to open an avenue for sensors, absorbers, switches, and programmable devices in infrared wavelength range applications.

Electrothermally tunable terahertz cross-shaped metamaterial for opto-logic operation characteristics.

We propose and demonstrate a metamaterial design by integrating a microelectromechanical system (MEMS) electrothermal actuator (ETA) platform and a cross-shaped metamaterial (CSM) to perform opto-logic function characteristics. Reconfigurable and stretchable mechanisms of CSM are achieved by driving different DC bias voltages on ETA to improve the limitations induced by the conventional use of the flexible substrate. The optical responses of CSM are tunable by the electrical signals inputs. By driving a DC bias voltage of 0.20 V, a tuning range of CSM is 0.54 THz is obtained and it and provides perfect zero-transmission characteristics. In addition, the "XNOR" logic gate function of CSM is realized at 1.20 THz, which plays a key role in the all opto-logic network communication system. The proposed MEMS-based CSM exhibits potential applications in logical operation, signal modulation, optical switching, THz imaging, and so on.

Tunable Terahertz Metamaterial with Electromagnetically Induced Transparency Characteristic for Sensing Application.

We present and demonstrate a MEMS-based tunable terahertz metamaterial (TTM) composed of inner triadius and outer electric split-ring resonator (eSRR) structures. With the aim to explore the electromagnetic responses of TTM device, different geometrical parameters are compared and discussed to optimize the suitable TTM design, including the length, radius, and height of TTM device. The height of triadius structure could be changed by using MEMS technique to perform active tunability. TTM shows the polarization-dependent and electromagnetic induced transparency (EIT) characteristics owing to the eSRR configuration. The electromagnetic responses of TTM exhibit tunable characteristics in resonance, polarization-dependent, and electromagnetically induced transparency (EIT). By properly tailoring the length and height of the inner triadius structure and the radius of the outer eSRR structure, the corresponding resonance tuning range reaches 0.32 THz. In addition to the above optical characteristics of TTM, we further investigate its potential application in a refraction index sensor. TTM is exposed on the surrounding ambient with different refraction indexes. The corresponding key sensing performances, such as figure of merit (FOM), sensitivity (S), and quality factor (Q-factor) values, are calculated and discussed, respectively. The calculated sensitivity of TTM is 0.379 THz/RIU, while the average values of Q-factor and FOM are 66.01 and 63.83, respectively. These characteristics indicate that the presented MEMS-based TTM device could be widely used in tunable filters, perfect absorbers, high-efficient environmental sensors, and optical switches applications for THz-wave optoelectronics.

Gene cloning, analysis and effect of a new lipocalin homologue from Haemaphysalis longicornis as a protective antigen for an anti-tick vaccine.

Haemaphysalis longicornis is distributed worldwide and transmits a variety of pathogens, causing human and animal disease. Use of chemical acaricides, as a primary tick control method, has several disadvantages, including acaricide resistance, environmental damage and residue accumulation in livestock. Development of a livestock vaccination aimed at a tick protective antigen could be an effective, labor-saving and environmentally-friendly method of reducing tick infestation and transmission of tick-borne pathogens. Lipocalins are low molecular weight proteins that play important roles in blood feeding, immune response and reproduction in ticks. In our study, the open reading frame (ORF) of a lipocalin homologue from H. longicornis (HlLIP) was successfully cloned, which consisted of 387 bp encoding a protein of 128 amino acids. The HlLIP protein sequence showed a close sequence homology with Ixodes persulcatus lipocalin. The HlLIP gene was constitutively detected in all developmental stages and in all tissues of the unfed female tick. The ORF of the HlLIP gene was sub-cloned into pET-32a (+) to obtain the recombinant protein (rHlLIP) and its immunogenicity was comfirmed by western blot. A vaccination trial on rabbits against H. longicornis infestation demonstrated that the rHlLIP protein could significantly prolong the period of tick blood feeding, and reduce tick engorged weight, oviposition and egg hatching rate. The vaccination efficacy of the rHlLIP protein was 60.17 % based on engorged weight, oviposition and egg hatching rate of ticks. The results obtained in this study demonstrate that rHlLIP protein is a promising antigen that could potentially be developed as a vaccine against H. longicornis infestation.