Phytochrome-interacting factors play shared and distinct roles in regulating shade avoidance responses in Populus trees.

Plants adjust their growth and development in response to changing light caused by canopy shade. The molecular mechanisms underlying shade avoidance responses have been widely studied in Arabidopsis and annual crop species, yet the shade avoidance signalling in woody perennial trees remains poorly understood. Here, we first showed that PtophyB1/2 photoreceptors serve conserved roles in attenuating the shade avoidance syndrome (SAS) in poplars. Next, we conducted a systematic identification and characterization of eight PtoPIF genes in Populus tomentosa. Knocking out different PtoPIFs led to attenuated shade responses to varying extents, whereas overexpression of PtoPIFs, particularly PtoPIF3.1 and PtoPIF3.2, led to constitutive SAS phenotypes under normal light and enhanced SAS responses under simulated shade. Notably, our results revealed that distinct from Arabidopsis PIF4 and PIF5, which are major regulators of SAS, the Populus homologues PtoPIF4.1 and PtoPIF4.2 seem to play a minor role in controlling shade responses. Moreover, we showed that PtoPIF3.1/3.2 could directly activate the expression of the auxin biosynthetic gene PtoYUC8 in response to shade, suggesting a conserved PIF-YUC-auxin pathway in modulating SAS in tree. Overall, our study provides insights into shared and divergent functions of PtoPIF members in regulating various aspects of the SAS in Populus.

In situ generated PANI promoted flexible photoelectrochemical biosensor for ochratoxin A based on GOx-stuffed DNA hydrogel as enhancer.

A flexible photoelectrochemical (PEC) biosensor is proposed for the sensitive detection of ochratoxin A (OTA) based on glucose oxidase (GOx)-encapsulated target-responsive hydrogel, using Fenton reaction-mediated in situ formation of polyaniline (PANI) as signal amplified strategy. The target-responsive DNA hydrogels with high loading capacity can carry a large amount of GOx, which not only avoids laborious labeling process but also enhances the analytical performance. Upon introduction of target molecules, the hydrogel can be opened, and multiple GOx was released, thus producing lots of H2O2 via catalytic reduction of glucose. As a component of the Fenton reagent, H2O2 can react with the Fe2+ on the graphene oxidase-PAMAM-Fe2+ (GO-PAMAM-Fe2+) to generate Fe3+ and ·OH. This in turn can oxidize aniline and generate polyaniline (PANI), resulting in the enhancement of the photocurrent signal of GO-MoS2-CdS photoelectrode. The GO-PAMAM-Fe2+ as the neighborhood component of GO-MoS2-CdS-based photoactive material not only can increase the loading amount of Fe2+, but also can inhibit the decrease of photocurrent of GO-MoS2-CdS by direct modification of Fe2+ on the photoactive material. Moreover, the high loading capacity of DNA hydrogel can efficiently promote the performance of the PEC biosensor. The PEC biosensor exhibited satisfactory analytical performance for OTA with a linear range of 0.0001-0.1 ng/mL and a low detection limit of 0.05 pg/mL. It presents recommendable specificity, stability, and practical applications. Importantly, the PEC biosensor provides a new concept for construction of PEC biosensing platform.

High-Performance Photoelectrochemical Enzymatic Bioanalysis Based on a 3D Porous CuxO@TiO2 Film with a Solid-Liquid-Air Triphase Interface.

The accurate detection of H2O2 is crucial in oxidase-based cathodic photoelectrochemical enzymatic bioanalysis but will be easily compromised in the conventional photoelectrode-electrolyte diphase system due to the fluctuation of oxygen levels and the similar reduction potential between oxygen and H2O2. Herein, a solid-liquid-air triphase bio-photocathode based on a superhydrophobic three-dimensional (3D) porous micro-nano-hierarchical structured CuxO@TiO2 film that was constructed by controlling the wettability of the electrode surface is reported. The triphase photoelectrochemical system ensures an oxygen-rich interface microenvironment with constant and sufficiently high oxygen concentration. Moreover, the 3D porous micro-nano-hierarchical structures possess abundant active catalytic sites and a multidimensional electron transport pathway. The synergistic effect of the improved oxygen supply and the photoelectrode architecture greatly stabilizes and enhances the kinetics of the enzymatic reaction and H2O2 cathodic reaction, resulting in a 60-fold broader linear detection range and a higher accuracy compared with the conventional solid-liquid diphase system.

High temperature inhibits vascular development via the PIF4-miR166-HB15 module in Arabidopsis.

The plant vascular system is an elaborate network of conducting and supporting tissues that extends throughout the plant body, and its structure and function must be orchestrated with different environmental conditions. Under high temperature, plants display thin and lodging stems that may lead to decreased yield and quality of crops. However, the molecular mechanism underlying high-temperature-mediated regulation of vascular development is not known. Here, we show that Arabidopsis plants overexpressing the basic-helix-loop-helix (bHLH) transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4), a central regulator of high-temperature signaling, display fewer vascular bundles (VBs) and decreased secondary cell wall (SCW) thickening, mimicking the lodging inflorescence stems of high-temperature-grown wild-type plants. Rising temperature and elevated PIF4 expression reduced the expression of MIR166 and, concomitantly, elevated the expression of the downstream class III homeodomain leucine-zipper (HD-ZIP III) family gene HB15. Consistently, knockdown of miR166 and overexpression of HB15 led to inhibition of vascular development and SCW formation, whereas the hb15 mutant displayed the opposite phenotype in response to high temperature. Moreover, in vitro and in vivo assays verified that PIF4 binds to the promoters of several MIR166 genes and represses their expression. Our study establishes a direct functional link between PIF4 and the miR166-HB15 module in modulating vascular development and SCW thickening and consequently stem-lodging susceptibility at elevated temperatures.

Size and density adjustment of nanostructures in nanochannels for screening performance improvement.

Biomimetic solid-state nanochannel/nanopore with flexible geometric structures, mechanical robustness and multifunctional surfaces have attracted extensive attention in separation, catalysis, drug delivery and other fields. Nanostructures have been introduced in nanoconfines to compress substances passthrough for high-efficient screening. However, precise controls of the nanostructure's growth in nanoconfines is rare. Herein, we developed a method to control size and number density of nanoparticles in nanochannels by adjusting polydopamine reducing conditions, achieving (1) particle size increasing, density increasing; (2) particle size increasing, density decreasing; (3) particle size increasing, density invariant; (4) particle size invariant, density increasing. The nanoparticles compressed the space of functional molecules decorated on them. Increasing size and density of nanoparticle enhanced the steric hinderance of functional molecules decorated on them and improved the wetting and chirality screening through nanochannels.

[Study on the interaction of L-cysteine dipeptide with DNA].

In the present paper the interaction mechanism and mode of biologically active cysteine dipeptide (Cys-Cys) with DNA was studied by UV-Vis spectrophotometry and fluorescence spectroscopy using ethidium bromide as a fluorescence probe. The results showed that in the buffer solution of Tris-HCl (pH 7.20), at low concentration of Cys-Cys, the ultraviolet spectrum of DNA-Cys-Cys system produced hypochromic effect with increasing the concentration of Cys-Cys. When the concentration of Cys-Cys increased to some high extent, the ultraviolet spectrum of DNA-Cys-Cys system produced hyperchromic effect. Salt-effect experiment showed that the interaction is liable to be affected by the ionic strengths, suggesting the existence of electrostatic binding between Cys-Cys and DNA. The fluorescence of EB-DNA had quenching effect with increasing the concentration of Cys-Cys, and the Stern-Volmer equation indicated that the quenching process was a static one. According to the Lineweaver-Burk equation the binding constant was determined to be 1.640 x 10(4) L x mol(-1). From the above results it can be concluded that the interaction mode of Cys-Cys with DNA was mainly electrostatic binding. These findings could contribute to further investigation on the mechanism of oligopeptides interaction with DNA.

Role of outer surface probes for regulating ion gating of nanochannels.

Nanochannels with functional elements have shown promise for DNA sequencing, single-molecule sensing, and ion gating. Ionic current measurement is currently a benchmark, but is focused solely on the contribution from nanochannels' inner-wall functional elements (NIWFE); the attributes of functional elements at nanochannels' outer surface (NOSFE) are nearly ignored, and remain elusive. Here we show that the role of NOSFE and NIWFE for ion gating can be distinguished by constructing DNA architectures using dual-current readout. The established molecular switches have continuously tunable and reversible ion-gating ability. We find that NOSFE exhibits negligible ion-gating behavior, but it can produce a synergistic effect in alliance with NIWFE. Moreover, the high-efficiency gating systems display more noticeable synergistic effect than the low-efficiency ones. We also reveal that the probe amount of NOSFE and NIWFE is almost equally distributed in our biomimetic nanochannels, which is potentially a premise for the synergistic ion-gating phenomena.

Publisher Correction: Role of outer surface probes for regulating ion gating of nanochannels.

The original version of this Article contained an error in Fig. 3. The scale bars in Figs 3c and 3d were incorrectly labelled as 50 µA. In the correct version, the scale bars are labelled as 0.5 µA. This has now been corrected in both the PDF and HTML versions of the Article.