Selenium-Mediated Shaping of Citrus Rhizobiome for Promotion in Root Growth and Soil Phosphorus Activation.

Selenium (Se) has been widely reported to affect plant growth, nutrient cycling, and the rhizobiome. However, how Se shapes the rhizobiome and interacts with plants remains largely elusive. Pot and hydroponic experiments were employed to elucidate the regulatory mechanism of Se in the citrus rhizobiome. Compared to the control, soil Se application significantly increased the root biomass (34.7%) and markedly reduced rhizosphere HCl-P, H2O-P, NaHCO3-IP, and residual-P of citrus, which were related to the variation of citrus rhizobiome. Se primarily enriched Proteobacteria and Actinobacteria as well as the phosphorus (P) functional genes phod and pqqc. Further study revealed that Se altered the metabolite profile of root exudate, particularly enhancing the abundance of l-cyclopentylglycine, cycloleucine, l-proline, l-pipecolic acid, and inositol, which played a key role in reshaping the citrus rhizobiome. These metabolites could serve as both nutrient sources and signaling molecules, thus supporting the growth or chemotaxis of the functional microbes. These bacterial taxa have the potential to solubilize P or stimulate plant growth. These findings provide a novel mechanistic understanding of the intriguing interactions between Se, root exudate, and rhizosphere microbiomes, and demonstrate the potential for utilizing Se to regulate rhizobiome function and enhance soil P utilization in citrus cultivation.

Soil selenium enhanced the resistance of oilseed rape to Sclerotinia sclerotiorum by optimizing the plant microbiome.

Plant can recruit beneficial microbes to enhance their ability to resist disease. Selenium is well established as a beneficial element in plant growth, but its role in mediating microbial disease resistance remained poorly understood. Here, we investigated the correlation between selenium, oilseed rape rhizosphere microbes and Sclerotinia sclerotiorum. Soil application of 0.5 and 1.0 mg/kg selenium significantly increased the resistance of oilseed rape to Sclerotinia sclerotiorum compared with no selenium application, and the disease inhibition rate was higher than 20%. The disease resistance of oilseed rape was related to rhizosphere microorganisms, and beneficial bacteria isolated from the rhizosphere inhibited Sclerotinia stem rot. Burkholderia cepacia, and synthetic community enhanced plant disease resistance through transcriptional regulation and activated plant-induced systemic resistance to protect plants. Besides, inoculation of isolated bacteria optimized the bacterial community structure of leaves and enriched beneficial microorganisms such as Bacillus, Pseudomonas and Sphingomonas. Bacillus isolated from the leaves were sprayed on the detached leaves, and it also performed a significant inhibition effect on Sclerotinia sclerotiorum. Overall, our results suggested that selenium drive plant rhizosphere microorganisms to increase resistance to Sclerotinia sclerotiorum in oilseed rape.

Selenium and Bacillus proteolyticus SES increased Cu-Cd-Cr uptake by ryegrass: highlighting the significance of key taxa and soil enzyme activity.

Many studies have focused their attention on strategies to improve soil phytoremediation efficiency. In this study, a pot experiment was carried out to investigate whether Se and Bacillus proteolyticus SES promote Cu-Cd-Cr uptake by ryegrass. To explore the effect mechanism of Se and Bacillus proteolyticus SES, rhizosphere soil physiochemical properties and rhizosphere soil bacterial properties were determined further. The findings showed that Se and Bacillus proteolyticus SES reduced 23.04% Cu, 36.85% Cd, and 9.85% Cr from the rhizosphere soil of ryegrass. Further analysis revealed that soil pH, organic matter, soil enzyme activities, and soil microbial properties were changed with Se and Bacillus proteolyticus SES application. Notably, rhizosphere key taxa (Bacteroidetes, Actinobacteria, Firmicutes, Patescibacteria, Verrucomicrobia, Chloroflexi, etc.) were significantly enriched in rhizosphere soil of ryegrass, and those taxa abundance were positively correlated with soil heavy metal contents (P < 0.01). Our study also demonstrated that in terms of explaining variations of soil Cu-Cd-Cr content under Se and Bacillus proteolyticus SES treatment, soil enzyme activities (catalase and acid phosphatase) and soil microbe properties showed 42.5% and 12.2% contributions value, respectively. Overall, our study provided solid evidence again that Se and Bacillus proteolyticus SES facilitated phytoextraction of soil Cu-Cd-Cr, and elucidated the effect of soil key microorganism and chemical factor.

Efficacy of atrioventricular valve regurgitation in the first trimester for the diagnosis of atrioventricular septal defect.

PURPOSE: To investigate the efficacy of atrioventricular valve regurgitation (AVVR) for predicting atrioventricular septal defect (AVSD) in the first trimester. METHODS: We performed a prospective observational study, screening for complicated congenital heart diseases and AVVR in fetuses at 11 to 13+6 weeks of gestation by advanced dynamic flow in four-chamber view and three-vessel-trachea view. RESULTS: 43 549 fetuses at 11 to 13+6 weeks of gestation were screened by echocardiography, of which 37 cases were diagnosed with AVSD, including complete AVSD (31 cases), intermediate AVSD (3 cases) and partial AVSD (1 cases), undiagnosed intermediate AVSD (2 cases), and misdiagnosed case (2 cases). AVVR was observed in 34 cases (34/37) in the first trimester, 59. 46% (22/37) nuchal translucency greater than 95th percentile, 29. 73% (11/37) absence of nasal bone, 32. 43% (12/37) ductus venosus A wave inversion, and 40. 54% (15/37) had tricuspid regurgitation. The sensitivity of common AVVR in predicting AVSD is better than other ultrasonic indexes. CONCLUSIONS: AVVR can be used as an ultrasonic indicator to predict AVSD in the first trimester, which is beneficial to detect AVSD.

Se Ameliorates Cd Toxicity in Oilseed rape (Brassica napus L.) Seedlings by Inhibiting Cd Transporter Genes and Maintaining root Plasma Membrane Integrity.

Se (Selenium) has been reported to be an important protective agent to decreases Cd (Cadmium) induced toxic in plants. However, it remains unclear how Se mitigates the uptake of Cd and increased the resistance to Cd toxicity. Hydroponic experiments were arranged to investigate the changes of physiological properties, root cell membrane integrity and Cd-related transporter genes in rape seedlings. Comparison of the biomass between the addition of Se and the absence of Se under Cd exposure showed that the Cd-induced growth inhibition of rape seedlings was alleviated by Se. Cd decreased the photosynthetic rate (Pn), stomatal conductance (Gs) and photosynthetic pigment content including chlorophyll a, chlorophyll b and carotenoid. However, all these parameters were all significantly improved by Se addition. Moreover, exposure to Se resulted in a decrease in Cd concentration in both shoot and root, ranging from 4.28 to 27.2%. Notably, the application of Se at a concentration of 1 µmol L- 1 exhibited the best performance. Furthermore, Se enhanced cell membrane integrity and reduced superoxide anion levels, thereby contributing to the alleviation of cadmium toxicity in plants. More critically, Se decreased the expression levels of root Cd-related transporter genes BnIRT1, BnHMA2 and BnHMA4 under Cd stress, which are responsible for Cd transport and translocation. These results are important to increase crop growth and reduce Cd load in the food chain from metal toxicity management and agronomical point of view.

Selenium-induced rhizosphere microorganisms endow salt-sensitive soybeans with salt tolerance.

Soil salinization is a prevalent abiotic stress that adversely affects soybean production. Rhizosphere microorganisms have been shown to modulate the rhizosphere microenvironment of plants, leading to improved stress resistance. Selenium is known to optimize the rhizosphere microbial community, however, it remains uncertain whether selenium-induced rhizosphere microorganisms can enhance plant salt tolerance. In this study, we selected two soybean varieties, including salt-tolerant and salt-sensitive, and conducted pot experiments to explore the impact of selenium application on the structure and composition of the rhizosphere microbial community of soybean plants under salt stress. Four salt-tolerant bacteria from salt-tolerant soybean rhizosphere soil fertilized with selenium under salt stress were isolated, and their effects on improving salt tolerance in salt-sensitive soybean were also investigated. Our results showed that selenium application enhanced soybean salt tolerance by optimizing the structure of the plant rhizosphere microbial community and improving soil enzyme activities in both salt-tolerant and salt-sensitive varieties. Moreover, compared with salt-only treatment, inoculation of the four bacteria led to a significant increase in the plant height (7.2%-19.8%), aboveground fresh weight (57.3%-73.5%), SPAD value (8.4%-30.3%), and K+ content (4.5%-12.1%) of salt-sensitive soybean, while reducing the content of proline (84.5%-94%), MDA (26.5%-49.3%), and Na+ (7.1%-21.3%). High-throughput sequencing of the 16 S ribosomal RNA gene indicated that the four bacteria played a crucial role in changing the community structure of salt-sensitive soybean and mitigating the effects of salt stress. This study highlighted the importance of selenium combined with beneficial microorganisms in the plant rhizosphere in alleviating salinity stress.

Selenium-mediated Cr(VI) reduction and SeNPs synthesis accelerated Bacillus cereus SES to remediate Cr contamination.

Microbial biotransformation of Cr(VI) is a sustainable approach to reduce Cr(VI) toxicity and remediate Cr(VI) contamination. In this study, Bacillus cereus SES with the capability of reducing both Cr(VI) and Se(IV) was isolated, and the effect of Se supplementation on Cr(VI) reduction by Bacillus cereus SES was investigated. Se(IV) addition enabled 2.6-fold faster Cr(VI) reduction, while B. cereus SES reduced 96.96% Se(IV) and produced more selenium nanoparticles (SeNPs) in the presence of Cr(VI). Co-reduction products of B. cereus SES on Cr(VI) and Se(IV) were SeNPs adsorbed with Cr(III). The relevant mechanisms were further revealed by proteomics. Se(IV) supplementation mediated the synthesis of Cr(VI) reductants and stress-resistant substances, thus enhancing Cr(VI) resistance and promoting Cr(VI) reduction. Meanwhile, high Se(IV) reduction rate was associated with Cr(VI)-induced electron transport processes, and Cr(VI) mediated the up-regulation of flagellar assembly, protein export and ABC transporters pathways to synthesis and export more SeNPs. Furthermore, Se combined with B. cereus SES had the potential to reduce the toxicity of Cr(VI) via reducing the bioavailability of Cr and improving the bioavailability of Se in soil. Results suggested that Se could be an efficient strategy to enhance the remediation of B. cereus SES on Cr contamination.

Selenium and Bacillus proteolyticus SES synergistically enhanced ryegrass to remediate Cu-Cd-Cr contaminated soil.

Heavy metal compound contaminated soil is an ecological threat, and soil containing copper (Cu), cadmium (Cd) and chromium (Cr) simultaneously is widely distributed. The application of phytoremediation in heavy metal combined contamination is still limited. In this study, to explore whether and how exogenous selenium (Se) and Bacillus proteolyticus SES enhance the remediation of combined Cu-Cd-Cr contaminated soil by ryegrass, pot experiments were carried out. Se alone or in combination with B. proteolyticus SES treatment increased the removal rates of heavy metals in the rhizosphere soil by 17.38%-157.25% relative to the control, while Se + B. proteolyticus SES treatment played a greater role in improving the heavy metals tolerance of ryegrass and increasing the activity of soil acid phosphatase. Moreover, Se and B. proteolyticus SES favored the preferential recruitment of specific taxa with the capacity of plant growth promotion and heavy metals resistance to the rhizosphere. The rhizosphere soil of Se treatment was specifically enriched with Lysobacter, Rhodanobacter, Micrococcales, Paenarthrobacter, and Adhaeribacter, while from class Bacilli to genus Bacillus enriched extensively and specifically in the rhizosphere of B. proteolyticus SES + Se treatment. Furthermore, five functional beneficial rhizosphere microbes including: Microbacterium sp., Pseudomonas extremaustralis, Bacillus amyloliquefaciens, Priestia megaterium, and Bacillus subtilis were isolated from the two treatments with the best remediation effect and synthetic communities (SynComs) were constructed. SynComs inoculation experiment further demonstrated the role of specific beneficial microbes in regulating the bioavailability of heavy metals. Results revealed that Se supplementation efficiently facilitated the phytoextraction of combined Cu-Cd-Cr contaminated soil, and B. proteolyticus SES inoculation showed the synergistical enhancement effect in the presence of Se.

Effects of Breathing Meditation Training on Sustained Attention Level, Mindfulness Attention Awareness Level, and Mental State of Operating Room Nurses.

OBJECTIVES: In this paper, we explore the effects of breathing meditation training on the sustained attention level, mindfulness attention awareness level, and mental state of nurses in the operating room. METHODS: We enrolled 40 nurses from September 2019 to December 2019, and divided them into a control group (N=20) and an observation group (N=20) using a random number table. The control group received routine training, based on which the observation group received breathing meditation training. We compared their sustained attention index, fatigue score, mindfulness attention awareness score, mental state score, work stress score, career satisfaction score, and career happiness index. RESULTS: After training, the sustained attention response time was shorter at 8:00 and 18:00 in the observation group than in the control group (p < .05). The physical fatigue score, mental fatigue score, reduced activity score, reduced motivation score, and overall fatigue score of the observation group were lower than those of the control group (p < .05). The observation group had a higher mindfulness attention awareness score than did the control group (p < .05). The SAS and SDS scores of the observation group were lower than those of the control group (p < .05). The work stress score of the observation group was lower than that of the control group, whereas the career satisfaction score and career happiness index were higher (p < .05). CONCLUSION: Breathing meditation training can improve the sustained attention level and mindfulness attention awareness level, reduce the feeling of fatigue and work stress, help adjust the mental state, and enhance the career satisfaction and career happiness of nurses in the operating room.

Chitin combined with selenium reduced nitrogen loss in soil and improved nitrogen uptake efficiency in Guanxi pomelo orchard.

Nitrogen cycling in soil, which associated with microbes, plays an important role in plant growth. Irrational application of nitrogen fertilizer could disrupt the structure of soil microbial community, thus inhibiting the uptake of nitrogen by plants and increasing nitrogen leaching in soil. Field and pot leaching experiments with the combined application of chitin fertilizer and selenium (Se) were carried out in order to develop an approach to improve the efficiency of nitrogen fertilizer utilization and reduce runoff by nitrogen loss in orchards of Guanxi pomelo in Fujian Province. Our results showed that application of chitin fertilizer combined with Se to the soil with reduced nitrogen and phosphate fertilizer (nitrogen fertilizer decreased by 25% and phosphate fertilizer decreased by 50%) could significantly increase the fruit yield, vitamin C and solid-acid ratio in the fruit. The application of chitin fertilizer and Se can not only lead to the increase of total nitrogen content in plant leaves but also the alkali-hydrolyzable nitrogen content in soil which enhancing soil nitrogen supplying capacity. It has been found that the adding the chitin fertilizer and Se into soil can significantly affect the structure and functional categories microbial communities and its activities. This is directly evidenced by the findings that the expression level of several groups of N metabolism and transporting related genes (i.e. amoAB and nxrA in nitrification, narG, nirK, norBC, and nosZ in denitrification, nirD, narH in dissimilatory nitrogen reduction, and ureC in ammoniation) has been drastically up-regulated. Our results indicate this strategy for reducing N and P input while maintaining and improving plant performance by supplementing with micronutrient Se and chitin fertilizer can increase the fruit yield and improve the quality of Guanxi pomelo through improving fertilizer use efficiency.

Soil applied Ca, Mg and B altered phyllosphere and rhizosphere bacterial microbiome and reduced Huanglongbing incidence in Gannan Navel Orange.

Huanglongbing (HLB) caused by 'Ca. Liberibacter. Asiaticus (Clas)' is one of the destructive diseases for citrus, threatening the development of citrus industry. Adopting a proper fertilization method instead of using pesticides seems particularly important, which would contribute to a sustainable development of orchard. In this study, the impact of soil application of nutrients combined with foliar spray of macro- and micro-nutrients on the incidence of HLB and the phyllosphere and rhizosphere bacterial microbiome was investigated in Gannan Navel Orange orchard from 2015 to 2018. Compared with the control (T1), the yield of Gannan Navel Orange in all other treatments applied with macro- and micro-nutrients increased significantly in 2018 (by 20.5%-45.8%), but not in the first two years (2016-17). Among treatments, Ca + Mg + B application in soil (T2) showed the highest yield and lowest HLB incidence. According to the PCR results, CLas was negative in T2 but positive in the control, which directly proved HLB incidence was reduced with Ca + Mg + B application in soil. Moreover, 16S rRNA sequencing was used to characterize rhizosphere and phyllosphere microbial communities. Results showed that microbial biodiversity was increased and microbial community structure was altered in T2 treatment, of which the beneficial bacteria were enriched in phyllosphere and rhizosphere. The results of PICRUSt showed that in T2 treatment, rhizosphere microbe contained more membrane transport (ABC transporters) genes, while, carbohydrate metabolism genes were enriched in the control rhizosphere due to HLB obstruct the photosynthetic metabolite transport. In summary, results indicated that macro- and micro-nutrients application improved the yield of Gannan Navel Orange and soil application of Ca + Mg + B reduced HLB incidence by altering microbial community structure and increasing microbial biodiversity. This study developed an environment-friendly way to reduce HLB incidence and improve the yield of citrus.

Enhancement and improvement of selenium in soil to the resistance of rape stem against Sclerotinia sclerotiorum and the inhibition of dissolved organic matter derived from rape straw on mycelium.

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (S. sclerotiorum), one of the most destructive diseases in many crops including Brassica napus L. The extensive use of fungicides to control S. sclerotiorum caused severe damage to the environment in the long term. Increasing study reported that selenium (Se) is a beneficial element for plant by promoting growth and enhancing disease resistance. In this study, it was found that Se in soil shortened lesion length by 19.14% on rape stem infected with S. sclerotiorum. While resistance mechanism of rape stem against S. sclerotiorum remains unknown. Transcriptomic analysis of rape stem was performed and the results indicated that genes related to antifungal pathways were up-regulated. Moreover, metabonomic analysis was carried out to study the inhibitive effect of the dissolved organic matter derived from rape straw with Se pretreatment in soil (RSDOMSe) on S. sclerotiorum mycelium, results showed that RSDOMSe caused severe damage to energy metabolism of mycelium. Further study indicated that RSDOMSe decreased the pathogenicity of mycelium on rape leaves significantly, and enhanced content of chlorophyII, carotenoids, OD phenol and activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) in rape leaves, which suggested that RSDOMSe plays a positive role in regulating oxidative stress responses of plant when infected with S. sclerotiorum. In addition, when compared with dimcthachlon (DIM) treatment alone, DIM combined with RSDOMSe resulted in higher inhibition on mycelial growth of S. sclerotiorum (the inhibition ratio of nearly 60%). Results in this study suggested that Se enhanced the resistance of rape stem against S. sclerotiorum because of the up-regulated genes related to antifungal pathways, and RSDOMSe improved the mycelial growth inhibition and decreased the pathogenicity of mycelium on rape leaves. Overall, Se as well as Se-enrich byproducts, possessed great potential to be developed as ecological fungicides for controlling S. sclerotiorum.

Isolation and characterization of Populus xyloglucan endotransglycosylase/hydrolase (XTH) involved in osmotic stress responses.

Xyloglucan endotransglycosylase/hydrolase (XTH) belongs to the GH16 subfamily of the glycoside hydrolases of carbohydrate active enzymes and plays an important role in the structure and function of plant cell walls. In this study, 11 members of the XTH gene family were cloned from Populus tomentosa. A bioinformatics analysis revealed that 11 PtoXTHs could be classified into three groups, where PtoXTH27 and PtoXTH34 were most likely to exhibit XTH activity. Biochemical analyses of purified PtoXTHs demonstrated that PtoXTH27 and PtoXTH34 had detectable xyloglucan endotransglucosylase (XET) activity, while the others did not exhibit XET or XEH activity. Moreover, enzymatic assays revealed that the optimum reaction temperature of both PtoXTH27 and PtoXTH34 was 37 °C, while their optimum pH values differed, such that PtoXTH27 was 6.0 and PtoXTH34 was 5.0. Enzyme kinetic parameters indicated that PtoXTH34 had higher affinity for the receptor substrate, XXXG, implying that PtoXTH34 and PtoXTH27 in plants have different substrate structure specificity. Finally, heterologous expression of XTH significantly increased intracellular total sugar content and osmotolerance of yeast cells, indicating that PtoXTH27 and PtoXTH34 are potentially involved in osmotic stress responses. These results clearly demonstrate the enzymatic characteristics and putative role of XTH in osmotic stress responses.

Selenium reduces the pathogenicity of Sclerotinia sclerotiorum by inhibiting sclerotial formation and germination.

Sclerotinia sclerotiorum (S. sclerotiorum) is a devastating fungal pathogen with worldwide distribution, and threatened the agro-ecological safety in the long term. To control the damage caused by Sclerotinia diseases, as well as consider the fungicide resistance and chemical residues, strategy of which plant nutritional regulation, as an eco-friendly approach, is gaining much significance. Selenium (Se), as a beneficial microelement for plant, has been manifested to be effective in inhibiting the mycelial growth of S.sclerotiorum in our previous study. In the present study, we observed that Se (both selenate and selenite) inhibited the formation of sclerotia, which is an important life form in the disease cycle of S. sclerotiorum. And the inhibition ratios of number of sclerotia in treatments of Se(VI)5.0 and Se(IV)5.0 were 54.55% and 43.84%, respectively; the inhibition ratios of weight of sclerotia in treatments of Se(VI)5.0 and Se(IV)5.0 were 42.29% and 25.67%, respectively. Results suggested that Se inhibited mycelial growth, severely damaged sclerotial ultrastructure, reduced the capacity of acid production, decreased superoxide dismutase (SOD) and catalase (CAT) activities, increased the content of hydrogen peroxide (H2O2) and superoxide anion (O2-) in mycelium, and all of these resulted in the reduction in sclerotial formation. Further studies revealed that Se application in medium increased Se concentration in sclerotia and thus inhibited sclerotial germination. Moreover, the pathogenicity of mycelia germinating from sclerotia that pretreated with Se, decreased significantly to rape leaves. These findings broadened our understanding of Se application in plant protection, as well as provided evidences for developing environment-friendly fungicide for S. sclerotiorum control.

Global vs local modularity for network community detection.

Community structures are ubiquitous in various complex networks, implying that the networks commonly be composed of groups of nodes with more internal links and less external links. As an important topic in network theory, community detection is of importance for understanding the structure and function of the networks. Optimizing statistical measures for community structures is one of most popular strategies for community detection in complex networks. In the paper, by using a type of self-loop rescaling strategy, we introduced a set of global modularity functions and a set of local modularity functions for community detection in networks, which are optimized by a kind of the self-consistent method. We carefully compared and analyzed the behaviors of the modularity-based methods in community detection, and confirmed the superiority of the local modularity for detecting community structures on large-size and heterogeneous networks. The local modularity can more quickly eliminate the first-type limit of modularity, and can eliminate or alleviate the second-type limit of modularity in networks, because of the use of the local information in networks. Moreover, we tested the methods in real networks. Finally, we expect the research can provide useful insight into the problem of community detection in complex networks.