Double-Stranded RNA-Degrading Enzymes Reduce the Efficiency of RNA Interference in Plutella xylostella.

DsRNA-degrading enzymes (dsRNases) have been recognized as important factors in reducing RNA interference (RNAi) efficiency in different insect species. However, dsRNases in Plutella xylostella are still unknown. We identified the full-length cDNAs of PxdsRNase1, PxdsRNase2, PxdsRNase3, and PxdsRNase4. Gene expression profile showed that PxdsRNase1 was mainly expressed in the hemolymph; and that PxdsRNase2 and PxdsRNase3 were mainly expressed in the intestinal tract. The expression of PxCht (Chitinase of P. xylostella) in P. xylostella larvae injected with the mixture of dsPxCht (dsRNA of PxCht) and dsPxdsRNase1 (dsRNA of PxdsRNase1), dsPxdsRNase2 (dsRNA of PxdsRNase2), or dsPxdsRNase3 (dsRNA of PxdsRNase3) was significantly higher than that in the larvae injected with the mixture of dsGFP (dsRNA of green fluorescent protein gene, GFP) and dsPxCht; the transcription level of PxCht in the larvae feeding on the mixture of dsPxCht and dsPxdsRNase1, dsPxdsRNase2, or dsPxdsRNase3 was significantly higher than that in the larvae feeding on the mixture of dsPxCht and dsGFP. The recombinant protein of PxdsRNase1 degraded dsRNA rapidly, PxdsRNase3 cleaved dsRNA without complete degradation, and PxdsRNase2 could not degrade dsRNA in vitro. These results suggested that PxdsRNases1, PxdsRNases2, and PxdsRNases3 were involved in the dsRNA degradation to reduce RNAi efficiency with different mechanisms.

The Combination of Bacillus Thuringiensis and Its Engineered Strain Expressing dsRNA Increases the Toxicity against Plutella Xylostella.

RNA interference (RNAi) has been developed and used as an emerging strategy for pest management. Here, an entomopathogen Bacillus thuringiensis (Bt) was used to express the dsRNA for the control of Plutella xylostella. A vector containing a 325-bp fragment of the conserved region of P. xylostella arginine kinase gene (PxAK) flanking in two ends with the promoter Pro3α was developed and transferred into Bt 8010 and BMB171, and consequently engineered Bt strains 8010AKi and BMB171AKi expressing dsRNA of PxAK were developed. The two engineered Bt strains were separately mixed with Bt 8010 in a series of ratios, and then fed to the P. xylostella larvae. We found that 8010:8010AKi of 9:1 and 8010:BMB171AKi of 7:3 caused a higher mortality than Bt 8010. PxAK expression levels in the individuals treated with the mixtures, 8010AKi and BMB171Aki, were lower than that in the control. The intrinsic rate of increase (r) and net reproductive rate (R0) of the population treated with 8010:8010AKi of 9:1 were lower than those of the population treated with Bt 8010 or 8010AKi. We developed a Bt-mediated insect RNAi for the control of P. xylostella and demonstrated a practical approach to integrating the entomopathogen with RNAi technique for the pest management.

A fluorescein-coumarin based ratiometric fluorescent probe for detecting hydrazine and its real applications in cells imaging.

According to the mechanism of hydrazine to ester bond elimination, a novel ratiometric fluorescent probe (FCP) based on the fluorescein-coumarin structure is designed and synthesized for detecting hydrazine. The obvious red shift in the absorption and fluorescence spectrum is caused by the hydrolysis of the ester bond of FCP by upon mixing with hydrazine. The proposed FCP probe is shown to have linear detection ranges from 0 to 250 nM for hydrazine, and LOD is 0.364 nM. In addition, this promising probe possesses high sensitivity and selectivity for monitoring the intracellular hydrazine, thus, has great potential to be applied in early diagnosis of disease. Meanwhile, it has been successfully applied to the detection and cell imaging of hydrazine in actual water samples.

Designing enhanced and ratiometric probes for detecting OCl- based on substituents influencing the fluorescence of HBT and their application in strips and bioimaging.

Nitro groups with a strong electron-withdrawing effect can powerfully influence the fluorescence of fluorophores. In this work, through adjusting the nitro group at the HBT fluorophore to construct a phenylhydrazone structure, two probes (HBTN and HBTH) were synthesized to detect OCl-. Consequently, HBTN with the nitro group quenched the fluorescence of HBT and HBTH without the nitro group causing a redshift of the fluorescence, which resulted in enhanced and ratiometric fluorescence signal changes during the detection process. Among them, HBTN shows good ability to selectively detect OCl- in the concentration range of 0-14 µM with the detection limit of 2.06 nM. Based on HBTN, a portable test strip for detecting OCl- was made for the convenient quantification of the OCl- concentration with a spectrophotometer, and exogenous and endogenous OCl- was successfully imaged in cells.

Silencing arginine kinase/integrin ß1 subunit by transgenic plant expressing dsRNA inhibits the development and survival of Plutella xylostella.

BACKGROUND: Plutella xylostella is a devastating agricultural insect pest of cruciferous plants, including crops. Plant-mediated RNA interference (RNAi) is currently being developed for plant protection. In this study, we investigated the response of P. xylostella exposed to transgenic Arabidopsis thaliana plants that expressed double-stranded RNA (dsRNA) targeting P. xylostella genes of arginine kinase (PxAK) and integrin ß1 subunit (Pxß). RESULTS: Transgenic plants producing dsRNAs of the 384-bp fragment of PxAK (dsAK plants), the 497-bp fragment of Pxß (dsß plants), and the 881 bp of the combination of both genes (dsAK-ß plants) were generated and verified. Insect bioassay with these transgenic plants showed that the development of P. xylostella was affected, causing longer developmental time, and lower pupal weight and pupation rate. P. xylostella mortality rates were 25.0% when exposed to dsAK plants, 22.5% with dsß plants, and 30.0% with dsAK-ß plants, which were all higher than 7.5% for the wild-type plant. PxAK and Pxß in P. xylostella were suppressed by 26.6-79.7% at the transcription level by the transgenic plants. CONCLUSION: These results suggest that plant-mediated RNAi targeting single gene or both PxAK and Pxß may have the potential to control P. xylostella. © 2019 Society of Chemical Industry.

4-aminoantipyrine modified carbon dots and their analytical applications through response surface methodology.

A sensitive and selective nanoprobe for detection of hypochlorite (OCl-) based on 4-aminoantipyrine (AAP) modified carbon dots (CDs-AAP) has been prepared. The CDs-AAP exhibit an emission peak at 484 nm when the excitation wavelength is 370 nm, accompanying 36 nm red shift compare with the pristine CDs. The addition of OCl- lead to the AAP on the surface of CDs experience a process of hydrazide hydrolysis and double bond addition, causing the singlet and triplet electrons of the excited state more closer in energy (ie, the energy difference between the two is reduced), eventually quenching the fluorescence of CDs due to heavy atomic effects. Central composite design (CCD) and response surface method (RSM) were used to optimize the detection variables of pH, incubation time and temperature. The designed model study indicated that the optimum detection conditions was pH 7.0, temperature 30 °C and incubation time 20 min, respectively. Under optimal conditions, the fluorescent intensity of the nanoprobe linearly responded to the OCl- concentration from 3 µM to 36 µM and the limit of detection was 40 nM. The proposed nanoprobe was successfully used to the detection of OCl- in tap water and pool water, and the recovery were in the range of 94% - 103%. In addition, the nanoprobe was also applied in imaging of VMSCs cells and labeling E.coli.

Novel fluorescein- and pyridine-conjugated schiff base probes for the recyclable real-time determination of Ce3+ and F.

The effect of aminopyridines substituted at different positions on the fluorescence properties deserves to be studied. Since 2-aminopyridyl-based probes have been reported, the effects of 3-aminopyridine and 4-aminopyridine on the performance of fluorescein probes were discussed in here. Two Schiff base fluorescein probes FN-1, FN-2 were designed and synthesized. Among them, since the ligand shows a highly selective and sensitive response to metal charge transfer (LMCT), the fluorescence of FN-1 can be quenched by Ce3+ ions in PBS buffer. At the same time, a specific precipitation reaction between Ce3+ and F- releases the free probe to restore the fluorescence of FN-1. Therefore, FN-1 can be used for the recyclable 'ON-OFF-ON' detection of Ce3+and F-. The detection limits for Ce3+and F- are 4.48 µM and 11.58 µM in concentration range of 0-50 µM and 0-150 µM. However, due to the para position of N and amino groups on 4-aminopyridine, the spatial structure of FN-2 cannot be complexed with ions, resulting in poor selectivity. Polyvinylidene fluoride (PVDF) membrane containing FN-1 were prepared for the real-time qualitative detection of Ce3+and F- in real water samples. FN-1 exhibits high water solubility and biocompatibility and has been successfully applied to biological imaging in vascular smooth muscle cells (VSMCs).

The fluorescence mechanism of carbon dots, and methods for tuning their emission color: a review.

Carbon dots (CDs) display tunable photoluminescence and excitation-wavelength dependent emission. The color of fluorescence is affected by electronic bandgap transitions of conjugated π-domains, surface defect states, local fluorophores and element doping. In this review (with 145 refs.), the studies performed in the past 5 years on the relationship between the fluorescence mechanism and modes for modulating the emission color of CDs are summarized. The applications of such CDs in sensors and assays are then outlined. A concluding section then gives an outlook and describes current challenges in the design of CDs with different emission colors. Graphical abstract Schematic representation of the relationship between the color-emitting (blue, green, yellow, red and multicolor) modulation of carbon dots and fluorescence mechanism including bandgap transitions of conjugated π-domains and surface defect states.

Enhanced fluorescence probes based on Schiff base for recognizing Cu2+ and effect of different substituents on spectra.

Three enhanced fluorescence probes based on Rhodamine B-Schiff base structure were synthesized for detecting Cu2+. The corresponding detection limits were found to be 0.25 µM, 0.15 µM and 0.18 µM. Binding ratio and binding sites were determined by Job's and nuclear magnetic titration experiments. The binding constants obtained by the Benesi-Hildebrand equation to be 341.0 M-0.5,1.8 × 104 M-1, and 265.4 M-0.5, respectively. As isomers, the different effects of probes on Cu2+ detection were researched. By adjusting the position and the size of the substituent group, the effects of binding sites and steric hindrance on the complexation ratio, response time and detection limit were discussed. Optimal spatial combination structure with Cu2+ was obtained through energy calculation. Detection mechanism of Rhodamine B ring opening based on the complex of the Schiff base with Cu2+ was confirmed. E. coli staining and detection of real water samples had expanded their applications.

Surface modification and chemical functionalization of carbon dots: a review.

Surface functional groups strongly affect the properties of carbon dots (CDs). Amino, carboxy, and hydroxy groups are most commonly encountered in CDs, and they can be introduced via covalent and noncovalent modification. This article (with 116 refs.) reviews the progress made in the past few years. Following an introduction into the field, a large section covers methods for covalent modification (via amide coupling reactions, silylation, and other reactions including esterification, sulfonylation and copolymerization). Next section reviews methods for noncovalent modifications (π interactions, complexation/chelation, and electrostatic interactions). The resulting modified CDs are powerful nanomaterials for targeting and extracting analytes, and in drug release. The modification of the surface also affects fluorescence quantum yields, complexation capacity, the color of fluorescence, and their quenching capability. Current challenges are critically assessed in the concluding section. Graphical abstract The modification methods of carbon dots (CDs) includes covalent and noncovalent. Covalent modifications include amidation, silylation, esterification, sulfonylation and copolymerization reaction. Noncovalent modifications include electrostatic interactions, complexation and π interactions.

Fluorescent probes for detecting cysteine.

Cysteine plays a crucial role in physiological processes. Therefore, it is necessary to develop a method for detecting cysteine. Fluorimetry has the advantages of convenient detection, short response time, high sensitivity and good selectivity. In this review, fluorescent probes that detect cysteine over the past three years are summarized based on structural features of fluorophores such as coumarin, BODIPY, rhodamine, fluorescein, CDs, QDs, etc and reaction groups including acrylate, aldehyde, halogen, 7-nitrobenzofurazan, etc. Then, effects of different combinations between fluorophores and response groups on probe properties and detection performances are discussed.