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The receptor for activated C kinase 1 (RACK1) is one member of the most important WD repeat–containing family of proteins found in all eukaryotes and is involved in multiple signaling pathways. However, compared with the progress in the area of mammalian RACK1, our understanding of the functions and molecular mechanisms of RACK1 in the regulation of plant growth and development is still in its infancy. In the present study, we investigated the roles of rice RACK1A gene (OsRACK1A) in controlling seed germination and its molecular mechanisms by generating a series of transgenic rice lines, of which OsRACK1A was either over-expressed or under-expressed. Our results showed that OsRACK1A positively regulated seed germination and negatively regulated the responses of seed germination to both exogenous ABA and H2O2. Inhibition of ABA biosynthesis had no enhancing effect on germination, whereas inhibition of ABA catabolism significantly suppressed germination. ABA inhibition on seed germination was almost fully recovered by exogenous H2O2 treatment. Quantitative analyses showed that endogenous ABA levels were significantly higher and H2O2 levels significantly lower in OsRACK1A-down regulated transgenic lines as compared with those in wildtype or OsRACK1A-up regulated lines. Quantitative real-time PCR analyses showed that the transcript levels of OsRbohs and amylase genes, RAmy1A and RAmy3D, were significantly lower in OsRACK1A-down regulated transgenic lines. It is concluded that OsRACK1A positively regulates seed germination by controlling endogenous levels of ABA and H2O2 and their interaction. [ABSTRACT FROM AUTHOR]

Maintenance of root growth is essential for plant adaptation to soil drying. Here, we tested the hypothesis that auxin transport is involved in mediating ABA's modulation by activating proton secretion in the root tip to maintain root growth under moderate water stress., Rice and Arabidopsis plants were raised under a hydroponic system and subjected to moderate water stress (−0.47 MPa) with polyethylene glycol ( PEG). ABA accumulation, auxin transport and plasma membrane H+- ATPase activity at the root tip were monitored in addition to the primary root elongation and root hair density., We found that moderate water stress increases ABA accumulation and auxin transport in the root apex. Additionally, ABA modulation is involved in the regulation of auxin transport in the root tip. The transported auxin activates the plasma membrane H+- ATPase to release more protons along the root tip in its adaption to moderate water stress. The proton secretion in the root tip is essential in maintaining or promoting primary root elongation and root hair development under moderate water stress., These results suggest that ABA accumulation modulates auxin transport in the root tip, which enhances proton secretion for maintaining root growth under moderate water stress. [ABSTRACT FROM AUTHOR]

The scaffold protein RACK1 (Receptor for Activated C Kinase 1) serves as an integrative point for diverse signal transduction pathways. The Arabidopsis genome contains three RACK1 orthologues, however, little is known about their functions. It is reported here that one member of this gene family, RACK1A, previously identified as the Arabidopsis homologue of the tobacco arcA gene, mediates hormone responses and plays a regulatory role in multiple developmental processes. RACK1A expresses ubiquitously in Arabidopsis. Loss-of-function mutations in RACK1A confer defects in multiple developmental processes including seed germination, leaf production, and flowering. rack1a mutants displayed reduced sensitivity to gibberellin and brassinosteroid in seed germination, hypersensitivity to abscisic acid in seed germination and early seedling development, and hyposensitivity to auxin in adventitious and lateral root formation. These results provide the first genetic evidence that RACK1A is involved in multiple signal transduction pathways. [ABSTRACT FROM PUBLISHER]

Summary Light and brassinosteroids (BR) are indispensable for plant growth and control cell division in the apical meristem. However, how external light signals cooperate with internal brassinosteroids to program root meristem development remains elusive. We reveal that the photoreceptor phytochrome B (phyB) guides the scaffold protein RACK1 to coordinate BR signaling for maintaining root meristematic activity. phyB and RACK1 promote early root meristem development. Mechanistically, RACK1 could reinforce the phyB–SPA1 association by interacting with both phyB and SPA1, which indirectly affects COP1‐dependent RACK1 degradation, resulting in the accumulation of RACK1 in roots. Subsequently, RACK1 interacts with BES1 to repress its DNA‐binding activity toward the target gene CYCD3;1, leading to the release of BES1‐mediated inhibition of CYCD3;1 transcription, and hence the promotion of root meristem development. Our study provides mechanistic insights into the regulation of root meristem development by combination of light and phytohormones signals through the photoreceptors and scaffold proteins. [ABSTRACT FROM AUTHOR]

We have explored a method to collect xylem sap using a Scholander pressure chamber for potted plants. Intact root system in pots which fitted the pressure chamber was pressurised at a pneumatic pressure numerically equal to the absolute value of shoot water potential. The rate of xylem flow obtained from the stem stump under such pressure was found similar to the rate of transpiration before detopping. The rate of pressurised flow from detop-ped roots was linearly related to the pressure applied in both well-watered and soil-dried plants. The osmotic concentration of the xylem sap was negatively related to the rate of volume flow, suggesting the necessity to collect xylem sap at in vivo flow rate if original solute concentration is to be evaluated. The concentration of ABA in the xylem sap, however, did not show such a relationship with water flux. Both well-watered and soil-dried plants showed the concentration of ABA in xylem sap largely stable with a range of volume flow rate, indicating a linear relationship between the rate of ABA delivery through xylem and that of volume flow. We also compared the concentrations of ABA in xylem sap sequentially collected from pressurised roots with that from detached shoots of the same plants. The concentration of ABA in the initial saps from shoots showed to be similar to that from roots. However, a decrease in the concentration of ABA in the xylem sap collected from detached leaf or twig was observed when more volume of sap was collected, which might also be dependent on the plant species and the volume of xylem vessels concerned. [ABSTRACT FROM AUTHOR]

Background: Monodehydroascorbate reductase (MDAR or MDHAR), which is responsible for growth, development and stress response in plants, is a key enzyme in the maintenance of the ascorbate acid (AsA) pool through the AsA-glutathione (AsA-GSH) cycle. High temperature affects a broad spectrum of cellular components and metabolism including AsA-GSH cycle in plants. In rice, however, the detailed roles of OsMDHAR4 in resistance against heat stress remains unclear.Results: Here, we report that OsMDHAR4 protein was localized to the chloroplasts. OsMDHAR4 expression was detected in all tissues surveyed and peaked in leaf blade. OsMDHAR4 was responsive to multiple stresses and was relatively strongly induced by heat treatment. In comparison with wild type, the osmdhar4 mutant exhibited improved tolerance to heat stress, whereas OsMDHAR4 overexpression lines exhibited enhanced sensitivity to heat stress. Moreover, we found that suppression of OsMDHAR4 promoted stomatal closure and hydrogen peroxide accumulation, and overexpression of OsMDHAR4 increased stomatal opening and decreased hydrogen peroxide content in rice leaves.Conclusions: Taken together, these results indicated that OsMDHAR4 negatively regulates tolerance to heat stress by mediating H2O2-induced stomatal closure in rice. [ABSTRACT FROM AUTHOR]

The emergence and wide global spread of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates are of great concern. This multicenter study aimed to investigate the molecular characteristics of CRKP isolates from inpatients in Wuhan, China. From June 2018 to March 2019, 74 nonduplicated CRKP clinical isolates were collected from six hospitals in Wuhan. We determined the minimum inhibitory concentrations of 18 antibiotics and used real-time polymerase chain reaction to detect the presence of disinfectant resistance genes qacEΔ1 and cepA. Pulsed-field gel electrophoresis was conducted to assess the genetic relatedness of isolates. Among the 74 CRKP isolates, the rates of resistance to carbapenems were high: 93.2% to ertapenem, 90.5% to imipenem, and 87.8% to meropenem. All isolates were resistant to at least one carbapenem antibiotic. Of the 74 isolates, 64.9% (48/74) were positive for qacEΔ1 and 93.2% (69/74) for cepA. QacEΔ1 and cepA were detected concomitantly in 46 isolates (62.2%), whereas only 4.1% (3/74) had no disinfectant resistance genes. Pulsed-field gel electrophoresis analysis clustered the 46 CRKP strains co-producing qacEΔ1 and cepA into 15 different clonal clusters (Types A to O). The most common clonal clusters were Type C (41.3%), Type E (13.0%), and Type J (8.7%). The study showed high rates of resistance to most antibiotics and high frequency of qacEΔ1 and cepA in CRKP isolates. Specific clonal dissemination of CRKP was detected within the same hospital or between different hospitals. Therefore, medical institutions should choose and use disinfectants correctly to prevent the spread of CRKP.

Objective: To investigate the contamination of antibiotic-resistant bacteria in air of different departments in hospital., Methods: From 2018.07 to 2021.06, 191 samples of the air-conditioning filter dust in three hospitals were collected. Antibiotic-resistant bacteria were isolated from the accumulated dust. The drug sensitivity test was conducted for Staphylococcus aureus, Acinetobacter baumannii and Enterobacteriaceae., Results: A total of 119 samples were detected antibiotic-resistant bacteria from 191 samples, and the detection rate was 62.30%. The detection rate of different departments from high to low was surgical ward(68.29%) >intensive care unit(ICU)(59.62%) >medical ward(57.92%). A total of 362 strains of antimicribial-resistant organisms were isolated, mainly were Acinetobacter(28.73%), Pseudomonas(22.10%), Bacillus(22.10%), Staphylococcus(9.12%), etc. Among them, 72 strains of target organisms were detected, and the detection rate was 19.89%(72/362), the detection rate of different target bacteria from high to low was Acinetobacter baumannii(12.71%)>Enterobacteriaceae(4.72%)>Staphylococcus aureus(2.76%)(P<0.05). The drug sensitivity test showed that 41 strains of antimicribial-resistant organisms were detected, and the detection rate was 56.94%(41/72), including carbapenem-resistant Acinetobacter baumannii(CR-ABA), methicillin-resistant Staphylococcus aureus(MRSA), carbapenem-resistant Enterobacteriaceae(CRE), etc.24 strains of multidrug-resistant organisms(MDROs) were detected and the detection rate was 58.54%(24/41). The detection rate of different departments from high to low was ICU(80.00%)>medical ward(60.00%)>surgical ward(46.15%)., Conclusion: There was contaminated by Acinetobacter baumannii, Staphylococcus aureus, Enterobacteriaceae in the air of hospitals, some of them were MDROs, mainly were detected in neurological ward, respiratory medical ward, hyroid and breast surgery ward, neurosurgery ward, cardiothoracic surgery ward, gallideulous surgical ICU and general ICU.

Objective: To conduct a continuous monitoring of the physical, chemical microbial indicators and overall biological toxicity for water quality in waterlogged urban areas., Methods: Monitoring sites were chosen in the waterlogging areas in the NanhuYayuan and Banqiao communities of Hongshan District, and the Xinhu village of Xinzhou District, Wuhan City. The South Lake, Yezhi Lake and Shahe River were selected as the corresponding surface water monitoring sites. Samples were collected in an extended period of time for the examination of physical, chemical microbial indicators and the determination of biological toxicity. Statistical analysis was performed using SPSS 11. 0 software package., Results: The water samples from waterlogged areas generally exhibited poor aesthetic aspects of drinking waters, and these indexes gradually deteriorated with prolonged waterlogging. Among the general chemical indexes, p H value was at an initialhigh level and decreased with time, permanganate index( oxygen consumed) remained at a high level( 3. 83-8. 16 mg/L), nitrite-nitrogen level gradually increased and stabilized for 2-3 days and then gradually decreased, chloride of the waterlogged samples and the corresponding surface water samples were correlated. Toxicological indicators( arsenic, lead, mercury) were not examined. For microbioligical indicators, fecal coliforms was detected at a rate of 47%, and negative result were revealed for pathogenic pathogenic microorganisms( Escherichia coli O157, Vibrio cholerae, Shigella, Salmonella, Staphylococcus aureus) and Rotavirus and Novovirus. The inhibition rate of samples on luminous intensity of Vibrio cholerae was less than 30%., Conclusion: Although the aesthetic aspects of drinking water were poor and organic and fecal contaminants were present, the risk of health hazards from skin or respiratory exposure was small for residents. After the floodwater subsided, routine preventive disinfection will be sufficient to ensure the safety for waterlogged urban areas. The result of the luminescent bacteria test were in good agreement with the toxicological indicators.

This study aims to investigate the antimicrobial susceptibility, molecular characteristics and virulence genes of community-acquired methicillin-resistant ITALIC! Staphylococcus aureus(CA-MRSA) isolates with skin and soft tissue infections (SSTIs). Outpatients with SSTIs visiting five medical and health institutions were enrolled from 2011 to 2013. Available ITALIC! S. aureus isolates were characterized by antimicrobial susceptibility testing, and detection of PVL genes. For CA-MRSA isolates, we performed typing of staphylococcal cassette chromosome ITALIC! mec(SCC ITALIC! mec), multi locus sequence typing (MLST) and carriage of 27 virulence genes. A total of 203 ITALIC! S. aureusstrains were isolated from 1400 outpatients with SSTIs, and 21 (10.3%) were CA-MRSA isolates. The positive rate of PVL genes among ITALIC! S. aureus, CA-MRSA and methicillin-susceptible ITALIC! S. aureus(MSSA) isolates were 39.4%, 71.4% and 35.7%, respectively. CA-MRSA strains had greater sensitivity to non-β-lactam antimicrobial agents. All CA-MRSA isolates belonged to SCC ITALIC! mecIV and V, accounting for 47.6% and 52.4%, respectively. ST59 was the most common lineage accounting for 76.2%; ST59-SCC ITALIC! mecIVa-PVL-positive clone was found to be the predominant clone, accounting for 38.1%. All CA-MRSA isolates were found to be positive for one or more virulence genes, 28.6% of isolates carried PVL, ITALIC! seb, ITALIC! sek, ITALIC! seq, ITALIC! hla, ITALIC! hlb, ITALIC! hldand ITALIC! hlg-2. CA-MRSA infections were relatively uncommon in outpatients with SSTIs, but they carried many virulence genes, ST59-SCC ITALIC! mecIV a-PVL-positive clone was the predominant clone in Wuhan, China., (© FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The receptor for activated C kinase 1 (RACK1) is one member of the most important WD repeat-containing family of proteins found in all eukaryotes and is involved in multiple signaling pathways. However, compared with the progress in the area of mammalian RACK1, our understanding of the functions and molecular mechanisms of RACK1 in the regulation of plant growth and development is still in its infancy. In the present study, we investigated the roles of rice RACK1A gene (OsRACK1A) in controlling seed germination and its molecular mechanisms by generating a series of transgenic rice lines, of which OsRACK1A was either over-expressed or under-expressed. Our results showed that OsRACK1A positively regulated seed germination and negatively regulated the responses of seed germination to both exogenous ABA and H2O2. Inhibition of ABA biosynthesis had no enhancing effect on germination, whereas inhibition of ABA catabolism significantly suppressed germination. ABA inhibition on seed germination was almost fully recovered by exogenous H2O2 treatment. Quantitative analyses showed that endogenous ABA levels were significantly higher and H2O2 levels significantly lower in OsRACK1A-down regulated transgenic lines as compared with those in wildtype or OsRACK1A-up regulated lines. Quantitative real-time PCR analyses showed that the transcript levels of OsRbohs and amylase genes, RAmy1A and RAmy3D, were significantly lower in OsRACK1A-down regulated transgenic lines. It is concluded that OsRACK1A positively regulates seed germination by controlling endogenous levels of ABA and H2O2 and their interaction.