Transcription factors PuPRE6/PuMYB12 and histone deacetylase PuHDAC9-like regulate sucrose levels in pear.

The improvement of fruit quality, in particular sugar content, has been a major goal of plant breeding programmes for many years. Here, 2 varieties of the Ussurian pear (Pyrus ussuriensis), Nanguo, and its high-sucrose accumulation bud sport, Nanhong, were used to study the molecular mechanisms regulating sucrose transport in fruits. Comparative transcriptome analysis showed that in Nanhong fruit, an MYB transcription factor, PuMYB12, and a sucrose transporter protein, PuSUT4-like, were expressed at higher levels, while a paclobutrazol resistance transcription factor, PuPRE6, and a histone deacetylase (HDAC), PuHDAC9-like, were expressed at lower levels in Nanguo fruit. PuSUT4-like silencing and overexpression experiments in Nanguo pear showed that PuSUT4-like is essential for sucrose transportation. PuPRE6 and PuMYB12 act as antagonistic complexes to regulate PuSUT4-like transcription and sucrose accumulation. The histone deacetylation levels of the PuMYB12 and PuSUT4-like promoters were higher in Nanguo fruit than in Nanhong fruit, and Y1H assays showed that HDAC PuHDAC9-like bound directly to the promoters of PuMYB12 and PuSUT4-like. Our results uncovered transcription regulation and epigenetic mechanisms underlying sucrose accumulation in pears.

Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2O2 Electrosynthesis.

The production of hydrogen peroxide (H2O2) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4@PC). The Co─O4@PC electrocatalyst shows promising potential in H2O2 electrosynthesis via 2e- ORR, providing a high H2O2 selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H2O2. In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4@PC as the cathode present long-term stability and high efficiency for H2O2 production. Particularly, a high H2O2 production rate of 0.25 mol g-1 cat h-1 at 0.6 V can be obtained by the flow cell. The in situ-generated H2O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.

Investigating the molecular mechanisms of Pseudalteromonas sp. LD-B1's algicidal effects on the harmful alga Heterosigma akashiwo.

Heterosigma akashiwo is a harmful algal bloom species that causes significant detrimental effects on marine ecosystems worldwide. The algicidal bacterium Pseudalteromonas sp. LD-B1 has demonstrated potential effectiveness in mitigating these blooms. However, the molecular mechanisms underlying LD-B1's inhibitory effects on H. akashiwo remain poorly understood. In this study, we employed the comprehensive methodology, including morphological observation, assessment of photosynthetic efficiency (Fv/Fm), and transcriptomic analysis, to investigate the response of H. akashiwo to LD-B1. Exposure to LD-B1 resulted in a rapid decline of H. akashiwo's Fv/Fm ratio, with cells transitioning to a rounded shape within 2 hours, subsequently undergoing structural collapse and cytoplasmic leakage. Transcriptomic data revealed sustained downregulation of photosynthetic genes, indicating impaired functionality of the photosynthetic system. Additionally, genes related to the respiratory electron transfer chain and antioxidant defenses were consistently downregulated, suggesting prolonged oxidative stress beyond the cellular antioxidative capacity. Notably, upregulation of autophagy-related genes was observed, indicating autophagic responses in the algal cells. This study elucidates the molecular basis of LD-B1's algicidal effects on H. akashiwo, advancing our understanding of algicidal mechanisms and contributing to the development of effective strategies for controlling harmful algal blooms.

Absolute Ranging with Time Delay Interferometry for Space-Borne Gravitational Wave Detection.

In future space-borne gravitational wave (GW) detectors, time delay interferometry (TDI) will be utilized to reduce the overwhelming noise, including the laser frequency noise and the clock noise etc., by time shifting and recombining the data streams in post-processing. The successful operation of TDI relies on absolute inter-satellite ranging with meter-level precision. In this work, we numerically and experimentally demonstrate a strategy for inter-satellite distance measurement. The distances can be coarsely determined using the technique of arm-locking ranging with a large non-ambiguity range, and subsequently TDI can be used for precise distance measurement (TDI ranging) by finding the minimum value of the power of the residual noises. The measurement principle is introduced. We carry out the numerical simulations, and the results show millimeter-level precision. Further, we perform the experimental verifications based on the fiber link, and the distances can be measured with better than 0.05 m uncertainty, which can well satisfy the requirement of time delay interferometry.

Time delay interferometry with a transfer oscillator.

In this work, we experimentally perform time delay interferometry by using a transfer oscillator, which is capable of reducing the laser frequency noise and the clock noise simultaneously in the post processing. The iodine frequency reference is coherently downconverted to the microwave frequency using a laser frequency comb. The residual noise of the downconversion network is 5 × 10-6Hz/Hz1/2 at 0.7 mHz, and 4 × 10-6Hz/Hz1/2 at 0.1 Hz, indicating high homology between the optical frequency and the microwave frequency. We carry out time delay interferometry with the aid of the electrical delay module, which can introduce large time delays. The results show that the laser frequency noise and the clock noise can be reduced simultaneously by ten and three orders of magnitude, respectively, in the frequency band from 0.1 mHz to 0.1 Hz. The performance of the noise reduction can reach 6 × 10-8Hz/Hz1/2 at 0.1 mHz, and 7 × 10-7Hz/Hz1/2 at 1 mHz, meeting the requirements of the space-borne gravitational wave detection. Our work will be able to offer an alternative method for the frequency comb-based time delay interferometry in the future space-borne gravitational wave detectors.

NUCLEOCYTOPLASMIC shuttling of ETHYLENE RESPONSE FACTOR 5 mediated by nitric oxide suppresses ethylene biosynthesis in apple fruit.

Nitric oxide (NO) is known to modulate the action of several phytohormones. This includes the gaseous hormone ethylene, but the molecular mechanisms underlying the effect of NO on ethylene biosynthesis are unclear. Here, we observed a decrease in endogenous NO abundance during apple (Malus domestica) fruit development and exogenous treatment of apple fruit with a NO donor suppressed ethylene production, suggesting that NO is a ripening suppressor. Expression of the transcription factor MdERF5 was activated by NO donor treatment. NO induced the nucleocytoplasmic shuttling of MdERF5 by modulating its interaction with the protein phosphatase, MdPP2C57. MdPP2C57-induced dephosphorylation of MdERF5 at Ser260 is sufficient to promote nuclear export of MdERF5. As a consequence of this export, MdERF5 proteins in the cytoplasm interacted with and suppressed the activity of MdACO1, an enzyme that converts 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. The NO-activated MdERF5 was observed to increase in abundance in the nucleus and bind to the promoter of the ACC synthase gene MdACS1 and directly suppress its transcription. Together, these results suggest that NO-activated nucleocytoplasmic MdERF5 suppresses the action of ethylene biosynthetic genes, thereby suppressing ethylene biosynthesis and limiting fruit ripening.

The mechanism for brassinosteroids suppressing climacteric fruit ripening.

The plant hormone ethylene is important for the ripening of climacteric fruit, such as pear (Pyrus ussuriensis), and the brassinosteroid (BR) class of phytohormones affects ethylene biosynthesis during ripening via an unknown molecular mechanism. Here, we observed that exogenous BR treatment suppressed ethylene production and delayed fruit ripening, whereas treatment with a BR biosynthesis inhibitor promoted ethylene production and accelerated fruit ripening in pear, suggesting BR is a ripening suppressor. The expression of the transcription factor BRASSINAZOLE-RESISTANT 1PuBZR1 was enhanced by BR treatment during pear fruit ripening. PuBZR1 interacted with PuACO1, which converts 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, and suppressed its activity. BR-activated PuBZR1 bound to the promoters of PuACO1 and of PuACS1a, which encodes ACC synthase, and directly suppressed their transcription. Moreover, PuBZR1 suppressed the expression of transcription factor PuERF2 by binding its promoter, and PuERF2 bound to the promoters of PuACO1 and PuACS1a. We concluded that PuBZR1 indirectly suppresses the transcription of PuACO1 and PuACS1a through its regulation of PuERF2. Ethylene production and expression profiles of corresponding apple (Malus domestica) homologs showed similar changes following epibrassinolide treatment. Together, these results suggest that BR-activated BZR1 suppresses ACO1 activity and the expression of ACO1 and ACS1, thereby reducing ethylene production and suppressing fruit ripening. This likely represents a conserved mechanism by which BR suppresses ethylene biosynthesis during climacteric fruit ripening.

Impedimetric aptasensor based on porphyrin-based covalent-organic framework for determination of diethylstilbestrol.

An impedimetric sensing strategy was developed for sensitively determining diethylstilbestrol (DES) based on a platform of porphyrin-containing covalent-organic framework (p-COF). The p-COF was synthesized using 5,10,15,20-tetra (4-aminophenyl) porphyrin (TAPP) and 1,3,6,8-tetrakis(4-formylphenyl) pyrene (TFPy) as building blocks via condensation reaction, for which p-COF was named as TAPP-TFPy-COF. Considering the large specific surface area (302.9 m2 g-1), high porosity, rich nitrogen functionality, superior electrochemical activity, and strong bioaffinity toward DNA strands, the TAPP-TFPy-COF-based platform exhibited enhanced, non-label, and amplified electrochemical signal, large number of immobilized DES-targeted aptamer strands, and fast-response toward the analyte. Electrochemical results reveal that the TAPP-TFPy-COF-based aptasensor promoted the sensing performance for the detection of DES, resulting in an extremely low limit of detection of 0.42 fg mL-1 within a DES concentration ranging from 1 fg mL-1 to 0.1 pg mL-1, which was substantially lower than those of most reported DES sensors. Furthermore, the TAPP-TFPy-COF-based aptasensor possessed outperformed stability, high selectivity, ascendant reproducibility, and acceptable applicability in diverse environments. The recovery values for DES detection in milk, tap water, and frozen shrimp were in the range 91.80-118.50% with low relative standard deviation of 0.11-4.26%. This work provides a new sensing electrochemical approach based on COF network for DES detection and shows a deep insight into the construction of COF-based biosensors, which can be extended to be used for other target compounds.

Weak-Light Phase-Locking Time Delay Interferometry with Optical Frequency Combs.

In the future space-borne gravitational wave (GW) detector, the optical transponder scheme, i.e., the phase-locking scheme, will be utilized so as to maintain the signal-to-noise ratio (SNR). In this case, the whole constellation will share one common laser equivalently, which enables the considerable simplification of time delay interferometry (TDI) combinations. Recently, and remarkably, the unique combination of TDI and optical frequency comb (OFC) has shown a bright prospect for the future space-borne missions. When the laser frequency noise and the clock noise are synchronized using OFC as the bridge, the data streams will be reasonably simplified. However, in the optical transponder scheme, the weak-light phase-locking (WLPL) loops could bring additional noises. In this work, we analyze the phase-locking scheme with OFC and transfer characteristics of the noises including the WLPL noise. We show that the WLPL noise can be efficiently reduced by using the specific TDI combination, and the cooperation of phase-locking and frequency combs can greatly simplify the post-processing.

Preparation and Characterization of Red Mud/Fly Ash Composite Material (RFCM) for Phosphate Removal.

In this study, a new red mud/fly ash composite material (RFCM) for phosphate removal was prepared by granulation and activation methods, using bauxite residue (red mud, RM) as the main raw material, adding with some fly ash and a few adhesives. The effects of different types of RM and adhesives on RFCM for phosphate removal were discussed. It was found that RFCM prepared from sintering red mud and cement waste performed better on phosphate removal than that prepared from Bayer red mud and common industrial adhesives. After calcination activated at appropriate temperature around 800-900℃, the specific surface area of RFCM increased, and new substances with hydroxyl (-OH) appeared on the surface of RFCM, which were the functional groups for phosphate removal. Mechanism of RFCM for phosphate removal was speculated as a combination of physical adsorption, chemical adsorption and chemical precipitation, which mainly depended on ligand exchange and chemical reaction. This research will provide a potential application of bauxite residue in environmental remediation.