tRNA modification enzyme MiaB connects environmental cues to activation of Pseudomonas aeruginosa type III secretion system

Pseudomonas aeruginosa, a major inhabitant of numerous environmental reservoirs, is a momentous opportunistic human pathogen associated with severe infections even death in the patients suffering from immune deficiencies or metabolic diseases. Type III secretion system (T3SS) employed by P. aeruginosa to inject effector proteins into host cells is one of the pivotal virulence factors pertaining to acute infections caused by this pathogen. Previous studies showed that P. aeruginosa T3SS is regulated by various environmental cues such as calcium concentration and the host signal spermidine. However, how T3SS is regulated and expressed particularly under the ever-changing environmental conditions remains largely elusive. In this study, we reported that a tRNA modification enzyme PA3980, designated as MiaB, positively regulated T3SS gene expression in P. aeruginosa and was essential for the induced cytotoxicity of human lung epithelial cells. Further genetic assays revealed that MiaB promoted T3SS gene expression by repressing the LadS-Gac/Rsm signaling pathway and through the T3SS master regulator ExsA. Interestingly, ladS, gacA, rsmY and rsmZ in the LadS-Gac/Rsm signaling pathway seemed potential targets under the independent regulation of MiaB. Moreover, expression of MiaB was found to be induced by the cAMP-dependent global regulator Vfr as well as the spermidine transporter-dependent signaling pathway and thereafter functioned to mediate their regulation on the T3SS gene expression. Together, these results revealed a novel regulatory mechanism for MiaB, with which it integrates different environmental cues to modulate T3SS gene expression in this important bacterial pathogen.

Study of the Semileptonic Decay Λ_{c}^{+}→Λe^{+}ν_{e}

The study of the Cabibbo-favored semileptonic decay Λ_{c}^{+}→Λe^{+}ν_{e} is reported using a 4.5  fb^{-1} data sample of e^{+}e^{-} annihilations collected at center-of-mass energies ranging from 4.600 GeV to 4.699 GeV with the BESIII detector at the BEPCII collider. The branching fraction of the decay is measured to be B(Λ_{c}^{+}→Λe^{+}ν_{e})=(3.56±0.11_{stat}±0.07_{syst})%, which is the most precise measurement to date. Furthermore, we perform an investigation of the internal dynamics in Λ_{c}^{+}→Λe^{+}ν_{e}. We provide the first direct comparisons of the differential decay rate and form factors with those predicted from lattice quantum chromodynamics (LQCD) calculations. Combining the measured branching fraction with a q^{2}-integrated rate predicted by LQCD, we determine |V_{cs}|=0.936±0.017_{B}±0.024_{LQCD}±0.007_{τ_{Λ_{c}}}.

Measurement of the Absolute Branching Fraction and Decay Asymmetry of Λ→nγ

The radiative hyperon decay Λ→nγ is studied using (10087±44)×10^{6}  J/ψ events collected with the BESIII detector operating at BEPCII. The absolute branching fraction of the decay Λ→nγ is determined to be (0.832±0.038_{stat}±0.054_{syst})×10^{-3}, which is a factor of 2.1 lower and 5.6 standard deviations different than the previous measurement. By analyzing the joint angular distribution of the decay products, the first determination of the decay asymmetry α_{γ} is reported with a value of -0.16±0.10_{stat}±0.05_{syst}.

Observation of an Isoscalar Resonance with Exotic J^{PC}=1^{-+} Quantum Numbers in J/ψ→γηη^{'}

Using a sample of (10.09±0.04)×10^{9}  J/ψ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/ψ→γηη^{'} is performed. The first observation of an isoscalar state with exotic quantum numbers J^{PC}=1^{-+}, denoted as η_{1}(1855), is reported in the process J/ψ→γη_{1}(1855) with η_{1}(1855)→ηη^{'}. Its mass and width are measured to be (1855±9_{-1}^{+6})  MeV/c^{2} and (188±18_{-8}^{+3})  MeV, respectively, where the first uncertainties are statistical and the second are systematic, and its statistical significance is estimated to be larger than 19σ.

System-on-chip approach microwave imaging reflectometer on DIII-D tokamak

System-on-chip millimeter wave integrated circuit technology is used on the two-dimensional millimeter-wave imaging reflectometer (MIR) upgrade for density fluctuation imaging on the DIII-D tokamak fusion plasma. Customized CMOS chips have been successfully developed for the transmitter module and receiver module array, covering the 55-75 GHz working band. The transmitter module has the capability of simultaneously launching eight tunable probe frequencies (>0 dBm output power each). The receiver enclosure contains 12 receiver modules in two vertical lines. The quasi-optical local oscillator coupling of previous MIR systems has been replaced with an internal active frequency multiplier chain for improved local oscillator power delivery and flexible installation in a narrow space together with improved shielding against electromagnetic interference. The 55-75 GHz low noise amplifier, used between the receiver antenna and the first-stage mixer, significantly improves module sensitivity and suppresses electronics noise. The receiver module has a 20 dB gain improvement compared with the mini-lens approach and better than -75 dBm sensitivity, and its electronics noise temperature has been reduced from 55 000 K down to 11 200 K. The V-band MIR system is developed for co-located multi-field investigation of MHD-scale fluctuations in the pedestal region with W-band electron cyclotron emission imaging on DIII-D tokamak.

Rhodotorula mucilaginosa-alternative sources of natural carotenoids, lipids, and enzymes for industrial use

Biotechnologically useful yeast strains have been receiving important attention worldwide for the demand of a wide range of industries. Rhodotorula mucilaginosa is recognized as a biotechnologically important yeast that has gained great interest as a promising platform strain, owing to the diverse substrate appetites, robust stress resistance, and other gratifying features. Due to its attractive properties, R. mucilaginosa has been regarded as an excellent candidate for the biorefinery of carotenoids, lipids, enzymes, and other functional bioproducts by utilizing low-cost agricultural waste materials as substrates. These compounds have aroused great interest as the potential alternative sources of health-promoting food products, substrates for so-called third-generation biodiesel, and dyes or functional ingredients for cosmetics. Furthermore, the use of R. mucilaginosa has rapidly increased as a result of advancements in fermentation for enhanced production of these valuable bioactive compounds. This review focuses on R. mucilaginosa in these advancements and summarizes its potential prospects as alternative sources of natural bioproducts.

Observation of an a_{0}-like State with Mass of 1.817 GeV in the Study of D_{s}^{+}→K_{S}^{0}K^{+}π^{0} Decays

Using e^{+}e^{-} annihilation data corresponding to an integrated luminosity of 6.32  fb^{-1} collected at center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform the first amplitude analysis of the decay D_{s}^{+}→K_{S}^{0}K^{+}π^{0} and determine the relative branching fractions and phases for intermediate processes. We observe an a_{0}-like state with mass of 1.817 GeV in its decay to K_{S}^{0}K^{+} for the first time. In addition, we measure the ratio {B[D_{s}^{+}→K[over ¯]^{*}(892)^{0}K^{+}]/B[D_{s}^{+}→K[over ¯]^{0}K^{*}(892)^{+}]} to be 2.35_{-0.23stat}^{+0.42}±0.10_{syst}. Finally, we provide a precision measurement of the absolute branching fraction B(D_{s}^{+}→K_{S}^{0}K^{+}π^{0})=(1.46±0.06_{stat}±0.05_{syst})%.

STRONG STAYGREEN inhibits DNA binding of PvNAP transcription factors during leaf senescence in switchgrass

Fine tuning the progression of leaf senescence is important for plant fitness in nature, while the "staygreen" phenotype with delayed leaf senescence has been considered a valuable agronomic trait in crop genetic improvement. In this study, a switchgrass (Panicum virgatum L.) CCCH-type Zinc finger gene, Strong Staygreen (PvSSG), was characterized as a suppressor of leaf senescence as overexpression or suppression of the gene led to delayed or accelerated leaf senescence, respectively. Transcriptomic analysis marked that chlorophyll (Chl) catabolic pathway genes were involved in the PvSSG-regulated leaf senescence. PvSSG was identified as a nucleus-localized protein with no transcriptional activity. By yeast two-hybrid screening, we identified its interacting proteins, including a pair of paralogous transcription factors, PvNAP1/2 (NAC-LIKE, ACTIVATED BY AP3/PI). Overexpression of PvNAPs led to precocious leaf senescence at least partially by directly targeting and transactivating Chl catabolic genes to promote Chl degradation. PvSSG, through protein-protein interaction, repressed the DNA-binding efficiency of PvNAPs and alleviated its transactivating effect on downstream genes, thereby functioning as a "brake" in the progression of leaf senescence. Moreover, overexpression of PvSSG resulted in up to 47% higher biomass yield and improved biomass feedstock quality, reiterating the importance of leaf senescence regulation in the genetic improvement of switchgrass and other feedstock crops.

Diagnosing the pedestal magnetic field and magnetohydrodynamics radial structure with pedestal-scrape of layer electron cyclotron emission radiation inversion in H-mode plasma (invited)

Forward modeling is used to interpret inversion patterns of the pedestal-Scrape of Layer (SOL) Electron Cyclotron Emission (ECE) in DIII-D H-mode experiments. The modeling not only significantly improves the ECE data interpretation quality but also leads to the potential measurements of (1) the magnetic field strength |B| at the separatrix, (2) the pedestal |B| evolution during an inter-Edge Localized Mode (ELM) period, and (3) the pedestal Magnetohydrodynamics (MHD) radial structure. The ECE shine-through effect leads to three types of pedestal-SOL radiation inversions that are discussed in this paper. The first type of inversion is the non-monotonic T_e,rad profile with respect to the major radius. Using the ECE frequency at the minimum T_e,rad, the inversion can be applied to measure the magnetic field |B| at the separatrix and calibrate the mapping of the ECE channels with respect to the separatrix. The second type of inversion refers to the opposite phase between the radiation fluctuations δT_e,rad at the pedestal and SOL. This δT_e,rad phase inversion is sensitive to density and temperature fluctuations at the pedestal foot and, thus, can be used to qualitatively measure the MHD radial structure. The third type of inversion appears when the pedestal and SOL T_e,rad evolve in an opposite trend, which can be used to infer the pedestal |B| field change during an inter-ELM period. The bandwidth effect on measuring δT_e,rad due to pedestal MHD is also investigated in the radiation modeling.

Precise Measurements of Decay Parameters and CP Asymmetry with Entangled Λ-Λ[over ¯] Pairs

Based on 10 billion J/ψ events collected at the BESIII experiment, a search for CP violation in Λ decay is performed in the difference between CP-odd decay parameters α_{-} for Λ→pπ^{-} and α_{+} for Λ[over ¯]→p[over ¯]π^{+} by using the process e^{+}e^{-}→J/ψ→ΛΛ[over ¯]. With a five-dimensional fit to the full angular distributions of the daughter baryon, the most precise values for the decay parameters are determined to be α_{-}=0.7519±0.0036±0.0024 and α_{+}=-0.7559±0.0036±0.0030, respectively. The Λ and Λ[over ¯] averaged value of the decay parameter is extracted to be α_{avg}=0.7542±0.0010±0.0024 with unprecedented accuracy. The CP asymmetry A_{CP}=(α_{-}+α_{+})/(α_{-}-α_{+}) is determined to be -0.0025±0.0046±0.0012, which is one of the most precise measurements in the baryon sector. The reported results for the decay parameter will play an important role in the studies of the polarizations and CP violations for the strange, charmed and beauty baryons.

First Observation of the Direct Production of the χ_{c1} in e^{+}e^{-} Annihilation

We study the direct production of the J^{PC}=1^{++} charmonium state χ_{c1}(1P) in electron-positron annihilation by carrying out an energy scan around the mass of the χ_{c1}(1P). The data were collected with the BESIII detector at the BEPCII collider. An interference pattern between the signal process e^{+}e^{-}→χ_{c1}(1P)→γJ/ψ→γμ^{+}μ^{-} and the background processes e^{+}e^{-}→γ_{ISR}J/ψ→γ_{ISR}μ^{+}μ^{-} and e^{+}e^{-}→γ_{ISR}μ^{+}μ^{-} is observed by combining all the data samples. The χ_{c1}(1P) signal is observed with a significance of 5.1σ. This is the first observation of a C-even state directly produced in e^{+}e^{-} annihilation. The electronic width of the χ_{c1}(1P) resonance is determined to be Γ_{ee}=(0.12_{-0.08}^{+0.13})  eV, which is of the same order of magnitude as theoretical calculations.

Evidence for a Neutral Near-Threshold Structure in the K_{S}^{0} Recoil-Mass Spectra in e^{+}e^{-}→K_{S}^{0}D_{s}^{+}D^{*-} and e^{+}e^{-}→K_{S}^{0}D_{s}^{*+}D^{-}

We study the processes e^{+}e^{-}→K_{S}^{0}D_{s}^{+}D^{*-} and e^{+}e^{-}→K_{S}^{0}D_{s}^{*+}D^{-}, as well as their charge conjugated processes, at five center-of-mass energies between 4.628 and 4.699 GeV, using data samples corresponding to an integrated luminosity of 3.8  fb^{-1} collected by the BESIII detector at the BEPCII storage ring. Based on a partial reconstruction technique, we find evidence of a structure near the thresholds for D_{s}^{+}D^{*-} and D_{s}^{*+}D^{-} production in the K_{S}^{0} recoil-mass spectrum, which we refer to as the Z_{cs}(3985)^{0}. Fitting with a Breit-Wigner line shape, we find the mass of the structure to be (3992.2±1.7±1.6)  MeV/c^{2} and the width to be (7.7_{-3.8}^{+4.1}±4.3)  MeV, where the first uncertainties are statistical and the second are systematic. The significance of the Z_{cs}(3985)^{0} signal is found to be 4.6σ including both the statistical and systematic uncertainty. We report the Born cross section multiplied by the branching fraction at different energy points. The mass of the Z_{cs}(3985)^{0} is close to that of the Z_{cs}(3985)^{+}. Assuming SU(3) symmetry, the cross section of the neutral channel is consistent with that of the charged one. Hence, we conclude that the Z_{cs}(3985)^{0} is the isospin partner of the Z_{cs}(3985)^{+}.

Observation of Resonance Structures in e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) and Mass Measurement of ψ_{2}(3823)

Using a data sample corresponding to an integrated luminosity of 11.3  fb^{-1} collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we measure the product of the e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) cross section and the branching fraction B[ψ_{2}(3823)→γχ_{c1}]. For the first time, resonance structure is observed in the cross section line shape of e^{+}e^{-}→π^{+}π^{-}ψ_{2}(3823) with significances exceeding 5σ. A fit to data with two coherent Breit-Wigner resonances modeling the sqrt[s]-dependent cross section yields M(R_{1})=4406.9±17.2±4.5  MeV/c^{2}, Γ(R_{1})=128.1±37.2±2.3  MeV, and M(R_{2})=4647.9±8.6±0.8  MeV/c^{2}, Γ(R_{2})=33.1±18.6±4.1  MeV. Though weakly disfavored by the data, a single resonance with M(R)=4417.5±26.2±3.5  MeV/c^{2}, Γ(R)=245±48±13  MeV is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the ψ_{2}(3823) state is measured as (3823.12±0.43±0.13)  MeV/c^{2}, which is the most precise measurement to date.

Toxic effects of microplastics in plants depend more by their surface functional groups than just accumulation contents

Differentially charged microplastics (MPs) engendered by plastic aging (e.g., plastic film) widely existed in the agricultural ecosystem, yet minimal was known about the toxic effects of MPs on plants and their absorption and accumulation characteristics. Root absorption largely determined the migration and accumulation risks of MPs in the soil-crop food chain. Here, five types of MPs exposure experiments of leaf lettuce were implemented to simulate root absorption by hydroponics. MPs exposure caused different degrees of growth inhibition, root lignification, root cell apoptosis, and oxidative stress responses; accelerated chlorophyll decomposition and hampered normal electron transfer within the PSII photosystem. Moreover, the uptake of essential elements by roots was inhibited to varying degrees due to the pore blockage in the cell wall and the hetero-aggregation of opposite charges after MPs exposure. MPs exposure observably up-regulated the organic metabolic pathways in roots, thus affecting MPs mobility and absorption through the electrostatic and hydrophobic interactions between the root exudations and MPs. Importantly, MPs penetrated the root extracellular cortex into the stele and were transported to the shoots by transpiration through xylem vessels based on confocal laser scanning microscopy and scanning electron microscopy images. Quantitative analysis of MPs indicated that their toxic effects on plants were determined to a greater extent by the types of surface functional groups than just their accumulation contents, that is, MPs were confirmed edible risks through crop food chain transfer, but bioaccumulation varied by surface functional groups.

Observation of a State X(2600) in the π^{+}π^{-}η' System in the Process J/ψ→γπ^{+}π^{-}η'

Based on (10087±44)×10^{6}  J/ψ events collected with the BESIII detector, the process J/ψ→γπ^{+}π^{-}η^{'} is studied using two largest decay channels of the η^{'} meson, η^{'}→γπ^{+}π^{-} and η^{'}→ηπ^{+}π^{-}, η→γγ. A new resonance, which we denote as the X(2600), is observed with a statistical significance larger than 20σ in the π^{+}π^{-}η^{'} invariant mass spectrum, and it has a connection to a structure around 1.5  GeV/c^{2} in the π^{+}π^{-} invariant mass spectrum. A simultaneous fit on the π^{+}π^{-}η^{'} and π^{+}π^{-} invariant mass spectra with the two η^{'} decay modes indicates that the mass and width of the X(2600) state are 2618.3±2.0_{-1.4}^{+16.3}  MeV/c^{2} and 195±5_{-17}^{+26}  MeV, where the first uncertainties are statistical, and the second systematic.

Observation of J/ψ Electromagnetic Dalitz Decays to X(1835), X(2120), and X(2370)

Using a sample of about 10^{10}  J/ψ events collected at a center-of-mass energy sqrt[s]=3.097  GeV with the BESIII detector, the electromagnetic Dalitz decays J/ψ→e^{+}e^{-}π^{+}π^{-}η^{'}, with η^{'}→γπ^{+}π^{-} and η^{'}→π^{+}π^{-}η, have been studied. The decay J/ψ→e^{+}e^{-}X(1835) is observed with a significance of 15σ, and also an e^{+}e^{-} invariant-mass dependent transition form factor of J/ψ→e^{+}e^{-}X(1835) is presented for the first time. The intermediate states X(2120) and X(2370) are also observed in the π^{+}π^{-}η^{'} invariant-mass spectrum with significances of 5.3σ and 7.3σ. The corresponding product branching fractions for J/ψ→e^{+}e^{-}X, X→π^{+}π^{-}η^{'} [X=X(1835), X(2120), and X(2370)] are reported.

The NAC factor LpNAL delays leaf senescence by repressing two chlorophyll catabolic genes in perennial ryegrass

Expression of chlorophyll (Chl) catabolic genes during leaf senescence is tightly controlled at the transcriptional level. Here, we identified a NAC family transcription factor, LpNAL, involved in regulating Chl catabolic genes via the yeast one-hybrid system based on truncated promoter analysis of STAYGREEN (LpSGR) in perennial ryegrass (Lolium perenne L.). LpNAL was found to be a transcriptional repressor, directly repressing LpSGR as well as the Chl b reductase gene, NONYELLOWING COLORING1. Perennial ryegrass plants over-expressing LpNAL exhibited delayed leaf senescence or stay-green phenotypes, whereas knocking down LpNAL using RNA interference accelerated leaf senescence. Comparative transcriptome analysis of leaves at 30 d after emergence in wild-type, LpNAL-overexpression, and knock-down transgenic plants revealed that LpNAL-regulated stay-green phenotypes possess altered light reactions of photosynthesis, antioxidant metabolism, ABA and ethylene synthesis and signaling, and Chl catabolism. Collectively, the transcriptional repressor LpNAL targets both Chl a and Chl b catabolic genes and acts as a brake to fine-tune the rate of Chl degradation during leaf senescence in perennial ryegrass.

Probing CP symmetry and weak phases with entangled double-strange baryons

Though immensely successful, the standard model of particle physics does not offer any explanation as to why our Universe contains so much more matter than antimatter. A key to a dynamically generated matter-antimatter asymmetry is the existence of processes that violate the combined charge conjugation and parity (CP) symmetry1. As such, precision tests of CP symmetry may be used to search for physics beyond the standard model. However, hadrons decay through an interplay of strong and weak processes, quantified in terms of relative phases between the amplitudes. Although previous experiments constructed CP observables that depend on both strong and weak phases, we present an approach where sequential two-body decays of entangled multi-strange baryon-antibaryon pairs provide a separation between these phases. Our method, exploiting spin entanglement between the double-strange Ξ- baryon and its antiparticle2 [Formula: see text], has enabled a direct determination of the weak-phase difference, (ξP - ξS) = (1.2 ± 3.4 ± 0.8) × 10-2 rad. Furthermore, three independent CP observables can be constructed from our measured parameters. The precision in the estimated parameters for a given data sample size is several orders of magnitude greater than achieved with previous methods3. Finally, we provide an independent measurement of the recently debated Λ decay parameter αΛ (refs. 4,5). The [Formula: see text] asymmetry is in agreement with and compatible in precision to the most precise previous measurement4.