Aims
To analyse effects and mechanisms of plant growth promotion mediated by Bacillus mycoides strain A3 (BmA3), in Arabidopsis thaliana seedlings.
Methods and Results
Bacillus mycoides strain A3 ...(BmA3) isolated from the bamboo rhizosphere produced phytohormones, including indole‐3‐acetic acid (IAA) and gibberellic acid (GA), and exhibited phosphate solubilization and radical scavenging activities. A. thaliana seedlings inoculated with BmA3 exhibited an altered root architecture including an increased number of lateral roots and root hairs. Likewise, enhanced photosynthetic efficiency through the accumulation of higher levels of chlorophyll and starch, and increased plant size and fresh weight were observed in the BmA3‐treated seedlings. This bacterial inoculation stimulated the antioxidant defence system by increasing the activities of catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and phenylalanine ammonia‐lyase (PAL). Secondary metabolites, including phenolic compounds, flavonoids and glucosinolates, were induced to higher levels in the BmA3‐treated plants. Under drought and heat stresses, lower levels of H2O2, malondialdehyde (MDA) and electrolyte leakage were noticed in the treated seedlings. Genes involved in the signalling pathway of jasmonic acid (JA) including MYC2 and lipoxygenase 1 (LOX1) and salicylic acid (SA) including SAR DEFICIENT 1 (SARD1) and CAM‐BINDING PROTEIN 60‐LIKE G (CBP60G), and the antioxidant defence system including Ascorbate peroxidase (AtAPX) and alternative oxidase (AOX) were upregulated in BmA3‐treated plants. Moreover, pathogenesis‐related protein 1 (PR‐1) and PR‐2, marker genes for disease resistance, as well as DREB2A and HsFA2, which function in abiotic stress regulation, were also upregulated.
Conclusions
BmA3 was able to activate JA and SA signalling pathways to induce plant growth and abiotic stress tolerance in A. thaliana seedlings.
Significance and Impact of Study
The plant growth promotion and increased stress tolerance induced by BmA3 were the result of the combined effects of microbial metabolites and activated host plant responses, including phytohormone signalling pathways and antioxidant defence systems.
It is commonly believed that visual short-term memory (VSTM) consists of a fixed number of "slots" in which items can be stored. An alternative theory in which memory resource is a continuous ...quantity distributed over all items seems to be refuted by the appearance of guessing in human responses. Here, we introduce a model in which resource is not only continuous but also variable across items and trials, causing random fluctuations in encoding precision. We tested this model against previous models using two VSTM paradigms and two feature dimensions. Our model accurately accounts for all aspects of the data, including apparent guessing, and outperforms slot models in formal model comparison. At the neural level, variability in precision might correspond to variability in neural population gain and doubly stochastic stimulus representation. Our results suggest that VSTM resource is continuous and variable rather than discrete and fixed and might explain why subjective experience of VSTM is not all or none.
Atomically thin two-dimensional (2D) metals may be key ingredients in next-generation quantum and optoelectronic devices. However, 2D metals must be stabilized against environmental degradation and ...integrated into heterostructure devices at the wafer scale. The high-energy interface between silicon carbide and epitaxial graphene provides an intriguing framework for stabilizing a diverse range of 2D metals. Here we demonstrate large-area, environmentally stable, single-crystal 2D gallium, indium and tin that are stabilized at the interface of epitaxial graphene and silicon carbide. The 2D metals are covalently bonded to SiC below but present a non-bonded interface to the graphene overlayer; that is, they are 'half van der Waals' metals with strong internal gradients in bonding character. These non-centrosymmetric 2D metals offer compelling opportunities for superconducting devices, topological phenomena and advanced optoelectronic properties. For example, the reported 2D Ga is a superconductor that combines six strongly coupled Ga-derived electron pockets with a large nearly free-electron Fermi surface that closely approaches the Dirac points of the graphene overlayer.
Reliable energy modules and higher-sensitivity, higher-density, lower-powered sensing systems are constantly required to develop wearable electronics and the Internet of Things technology. As an ...emerging technology, triboelectric nanogenerators have been potentially guiding the landscape of sustainable power units and energy-efficient sensors. However, the existing triboelectric series is primarily populated by polymers and rubbers, limiting triboelectric sensing plasticity to some extent owing to their stiff surface electronic structures. To enrich the current triboelectric group, we explore the triboelectric properties of the topological insulator nanofilm by Kelvin probe force microscopy and reveal its relatively positive electrification charging performance. Both the larger surface potential difference and the conductive surface states of the nanofilms synergistically improve the charge transfer behavior between the selected triboelectric media, endowing the topological insulator-based triboelectric nanogenerator with considerable output performance. Besides serving as a wearable power source, the ultra-compact device array demonstrates innovative system-level sensing capabilities, including precise monitoring of dynamic objects and real-time signal control at the human-machine interface. This work fills the blank between topological quantum matters and triboelectric nanogenerators and, more importantly, exploits the significant potential of topological insulator nanofilms for self-powered flexible/wearable electronics and scalable sensing technologies.
•A theoretical model integrating the literature of expectation–confirmation model, and online shopping was proposed.•Increasing trust and satisfaction will facilitate repurchase intention.•Habit ...exerts a moderating effect on the determinants of repeat purchase intention.•Satisfaction has significant influence on trust.•Perceived value, confirmation, and website quality are the predictors of satisfaction.
The success of online shopping depends on customers’ repeat purchasing. This study proposed a theoretical model by integrating the literature of expectation–confirmation model and online shopping to test the factors affecting repeat purchase intention in online group-buying. Data collected from 246 respondents were used to test the proposed model. The results show that trust and satisfaction are the strong predictors of repeat purchase intention. The results also reveal that satisfaction has significant influence on trust, whereas perceived value, confirmation, and website quality are the significant antecedents of satisfaction. Our results report that website quality has positive influence on perceived value. Finally, perceived value exerts stronger effect on repeat purchase intention for high-habit customers, whereas trust and satisfaction have higher influence on repeat purchase intention for low-habit customers. Implications and limitations are discussed.
Vulnerability mapping based on vulnerability indices is a pragmatic approach for highlighting the areas in a city where people are at the greatest risk of harm from heat, but the manner in which ...vulnerability is conceptualized influences the results.
We tested a generic national heat-vulnerability index, based on a 10-variable indicator framework, using data on heat-related hospitalizations in Phoenix, Arizona. We also identified potential local risk factors not included in the generic indicators.
To evaluate the accuracy of the generic index in a city-specific context, we used factor scores, derived from a factor analysis using census tract-level characteristics, as independent variables, and heat hospitalizations (with census tracts categorized as zero-, moderate-, or high-incidence) as dependent variables in a multinomial logistic regression model. We also compared the geographical differences between a vulnerability map derived from the generic index and one derived from actual heat-related hospitalizations at the census-tract scale.
We found that the national-indicator framework correctly classified just over half (54%) of census tracts in Phoenix. Compared with all census tracts, high-vulnerability tracts that were misclassified by the index as zero-vulnerability tracts had higher average income and higher proportions of residents with a duration of residency < 5 years.
The generic indicators of vulnerability are useful, but they are sensitive to scale, measurement, and context. Decision makers need to consider the characteristics of their cities to determine how closely vulnerability maps based on generic indicators reflect actual risk of harm.
Expansion and contraction of inverted repeats can cause considerable variation of plastid genomes (plastomes) in angiosperms. However, little is known about whether structural variations of plastomes ...are associated with adaptation to or occupancy of new environments. Moreover, adaptive evolution of angiosperm plastid genes remains poorly understood. Here, we sequenced the complete plastomes for four species of xerophytic Ceratocephala and hydrophytic Myosurus, as well as Ficaria verna. By an integration of phylogenomic, comparative genomic, and selection pressure analyses, we investigated evolutionary patterns of plastomes in Ranunculeae and their relationships with adaptation to dry and aquatic habitats.
Owing to the significant contraction of the boundary of IR
/LSC towards the IR
, plastome sizes and IR lengths of Myosurus and Ceratocephala are smaller within Ranunculeae. Compared to other Ranunculeae, the Myosurus plastome lost clpP and rps16, one copy of rpl2 and rpl23, and one intron of rpoC1 and rpl16, and the Ceratocephala plastome added an infA gene and lost one copy of rpl2 and two introns of clpP. A total of 11 plastid genes (14%) showed positive selection, two genes common to Myosurus and Ceratocephala, seven in Ceratocephala only, and two in Myosurus only. Four genes showed strong signals of episodic positive selection. The rps7 gene of Ceratocephala and the rpl32 and ycf4 genes of Myosurus showed an increase in the rate of variation close to 3.3 Ma.
The plastomic structure variations as well as the positive selection of two plastid genes might be related to the colonization of new environments by the common ancestor of Ceratocephala and Myosurus. The seven and two genes under positive selection might be related to the adaptation to dry and aquatic habitats in Ceratocephala and Myosurus, respectively. Moreover, intensified aridity and frequent sea-level fluctuations, as well as global cooling, might have favored an increased rate of change in some genes at about 3.3 Ma, associated with adaptation to dry and aquatic environments, respectively. These findings suggest that changing environments might have influenced structural variations of plastomes and fixed new mutations arising on some plastid genes owing to adaptation to specific habitats.
Silver nanoparticles (AgNPs) are widely used as antibacterial nanomaterials; however, the environmental impacts of AgNPs remain uncertain. In this study, Arabidopsis physiological responses and gene ...expression were investigated after exposure to 3 different morphologies of AgNPs. The triangular (47 ± 7 nm) and spherical (8 ± 2 nm) AgNPs exhibited the lowest and highest degrees of antimicrobial activity, respectively. The AgNP-induced phenotypic alterations in Arabidopsis were correlated with nanoparticle morphology and size, in which the decahedral AgNPs (45 ± 5 nm) induced the highest degree of root growth promotion (RGP); however, the spherical AgNPs exhibited no RGP and induced the highest levels of anthocyanin accumulation in Arabidopsis seedlings. The decahedral and spherical AgNPs induced the lowest and highest levels of Cu/Zn superoxide dismutase (CSD2) accumulation, respectively. Moreover, 3 morphologies of AgNPs induced protein accumulations including cell-division-cycle kinase 2 (CDC2), protochlorophyllide oxidoreductase (POR), and fructose-1,6 bisphosphate aldolase (FBA). Regarding transcription, the AgNPs induced the gene expression of indoleacetic acid protein 8 (IAA8), 9-cis-epoxycarotenoid dioxygenase (NCED3), and dehydration-responsive RD22. Additional studies have shown that AgNPs antagonized the aminocyclopropane-1-carboxylic acid (ACC)-derived inhibition of root elongation in Arabidopsis seedlings, as well as reduced the expression of ACC synthase 7 (ACS7) and ACC oxidase 2 (ACO2), suggesting that AgNPs acted as inhibitors of ethylene (ET) perception and could interfere with ET biosynthesis. In conclusion, AgNPs induce ROS accumulation and root growth promotion in Arabidopsis. AgNPs activate Arabidopsis gene expression involved in cellular events, including cell proliferation, metabolism, and hormone signaling pathways.
•AgNPs induced bifacial effects on plant growth.•ROS accumulation was correlated with the size and morphology of AgNPs.•AgNPs activated genes involved in multiple cellular events.•AgNPs are effective inhibitors of ethylene perception.
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