Genome-wide investigation and expression analysis of OSCA gene family in response to abiotic stress in alfalfa

Alfalfa is an excellent leguminous forage crop that is widely cultivated worldwide, but its yield and quality are often affected by drought and soil salinization. Hyperosmolality-gated calcium-permeable channel (OSCA) proteins are hyperosmotic calcium ion (Ca2+) receptors that play an essential role in regulating plant growth, development, and abiotic stress responses. However, no systematic analysis of the OSCA gene family has been conducted in alfalfa. In this study, a total of 14 OSCA genes were identified from the alfalfa genome and classified into three groups based on their sequence composition and phylogenetic relationships. Gene structure, conserved motifs and functional domain prediction showed that all MsOSCA genes had the same functional domain DUF221. Cis-acting element analysis showed that MsOSCA genes had many cis-regulatory elements in response to abiotic or biotic stresses and hormones. Tissue expression pattern analysis demonstrated that the MsOSCA genes had tissue-specific expression; for example, MsOSCA12 was only expressed in roots and leaves but not in stem and petiole tissues. Furthermore, RT–qPCR results indicated that the expression of MsOSCA genes was induced by abiotic stress (drought and salt) and hormones (JA, SA, and ABA). In particular, the expression levels of MsOSCA3, MsOSCA5, MsOSCA12 and MsOSCA13 were significantly increased under drought and salt stress, and MsOSCA7, MsOSCA10, MsOSCA12 and MsOSCA13 genes exhibited significant upregulation under plant hormone treatments, indicating that these genes play a positive role in drought, salt and hormone responses. Subcellular localization results showed that the MsOSCA3 protein was localized on the plasma membrane. This study provides a basis for understanding the biological information and further functional analysis of the MsOSCA gene family and provides candidate genes for stress resistance breeding in alfalfa

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Delineation of Radar Glacier Zones in the Antarctic Peninsula Using Polarimetric SAR

Climate change is a cause of the expansion of snowmelt phenomena in the Antarctic, and shifts in position of wet and dry snow lines have been considered as good indicators of climate changes. The impacts of climate change are observable by the delineation of significant position change of glacier zones. The principal limitation of current glacier zone classification methods by synthetic aperture radar (SAR) image is that it is difficult to discriminate dry-snow and wet-snow zones using only single-polarimetric radar backscattering intensity. This study tried to solve the problem using polarimetric SAR (PolSAR). Analysis indicates that polarimetric decomposition elements could be efficient characteristics to delineate radar glacier zones by recognition of principal backscatter patterns. Further, two radar glacier zone classification processes for polarimetric SAR are proposed: a supervised support vector machine (SVM) classification process and a simple decision-tree classification method. These methods enable reliable delineation of radar glacier zones in the Antarctic Peninsula. Polarimetric SAR, which provides more information about the scattering processes and target structure, proves to be an efficient tool for delineating radar glacier zones and snowmelt detection

Water Body Mapping Using Long Time Series Sentinel-1 SAR Data in Poyang Lake

Mapping water bodies with a high accuracy is necessary for water resource assessment, and mapping them rapidly is necessary for flood monitoring. Poyang Lake is the largest freshwater lake in China, and its wetland is one of the most important in the world. Poyang Lake is affected by floods from the Yangtze River basin every year, and the fluctuation of the water area and water level directly or indirectly affects the ecological environment of Poyang Lake. Synthetic Aperture Radar (SAR) is particularly suitable for large-scale water body mapping, as SAR allows data acquisition regardless of illumination and weather conditions. The two-satellite Sentinel-1 constellation, providing C-Band SAR data, passes over the Poyang Lake about five times a month. With its high temporal-spatial resolution, the Sentinel-1 SAR data can be used to accurately monitor the water body. After acquiring all the Sentinel-1 (1A and 1B) SAR data, to ensure the consistency of data processing, we propose the use of a Python and SeNtinel Application Platform (SNAP)-based engine (SARProcMod) to process the data and construct a Poyang Lake Sentinel-1 SAR dataset with a 10 m resolution. To extract water body information from Sentinel-1 SAR data, we propose an automatic classification engine based on a modified U-Net convolutional neural network (WaterUNet), which classifies all data using artificial sample datasets with a high validation accuracy. The results show that the maximum and minimum water areas in our study area were 2714.08 km2 on 20 July 2020, and 634.44 km2 on 4 January 2020. Compared to the water level data from the Poyang gauging station, the water area was highly correlated with the water level, with the correlation coefficient being up to 0.92 and the R2 from quadratic polynomial fitting up to 0.88; thus, the resulting relationship results can be used to estimate the water area or water level of Poyang Lake. According to the results, we can conclude that Sentinel-1 SAR and WaterUNet are very suitable for water body monitoring as well as emergency flood mapping

Dynamic Simulation of Land Use/Cover Change and Assessment of Forest Ecosystem Carbon Storage under Climate Change Scenarios in Guangdong Province, China

Exploring the spatial distribution of land use/cover change (LUCC) and ecosystem carbon storage under future climate change scenarios can provide the scientific basis for optimizing land resource redistribution and formulating policies for sustainable socioeconomic development. We proposed a framework that integrates the patch-generating land use simulation (PLUS) model and integrated valuation of ecosystem services and tradeoffs (InVEST) model to assess the spatiotemporal dynamic changes in LUCC and ecosystem carbon storage in Guangdong based on shared socioeconomic pathways and representative concentration pathways (SSP-RCP) scenarios provided by the Coupled Model Intercomparison Project 6 (CMIP6). The future simulation results showed that the distribution patterns of LUCC were similar under SSP126 and SSP245 scenarios, but the artificial surface expanded more rapidly, and the increase in forest land slowed down under the SPP245 scenario. Conversely, under the SSP585 scenario, the sharply expanded artificial surface resulted in a continuous decrease in forest land. Under the three scenarios, population, elevation, temperature, and distance to water were the highest contributing driving factors for the growth of cultivated land, forest land, grassland, and artificial surface, respectively. By 2060, the carbon storage in terrestrial ecosystems increased from 240.89 Tg in 2020 to 247.16 Tg and 243.54 Tg under SSP126 and SSP245 scenarios, respectively, of which forest ecosystem carbon storage increased by 17.65 Tg and 15.34 Tg, respectively; while it decreased to 226.54 Tg under the SSP585 scenario, and the decreased carbon storage due to forest destruction accounted for 81.05% of the total decreased carbon storage. Overall, an important recommendation from this study is that ecosystem carbon storage can be increased by controlling population and economic growth, and balancing urban expansion and ecological conservation, as well as increasing forest land area

Effects of land reclamation on soil bacterial community assembly and carbon sequestration function in coal mine subsidence area: taking Dongtan Mining Area as an example

Although the reclamation activity could effectively promote the ecological service function of mining areas, the microbiological mechanism of functional reconstruction of reclaimed soil is still unclear. Clarifying how reclamation affects the characteristics, assembly mechanisms, and carbon sequestration functions of soil bacterial communities, is crucial for reshaping the ecological self-sustaining capacity of mining areas. To shed light on this purpose, combined with zero model analysis, MiSeq high-throughput sequencing and qPCR SmartChip technologies were used to explore the assembly processes and carbon sequestration functional variations of soil bacterial community in Dongtan mine area at four reclamation years (reclaimed 9 a, 12 a, 15 a, and 18 a). The results showed that: ① Reclamation activity and time presented significant impacts on soil physicochemical properties and enzyme activities. Soil pH, ammonium nitrogen (AN), catalase (CAT), and alkaline phosphatase (PO) showed the significant increasing trends with the incremental reclamation time (P<0.05), whereas organic carbon (SOC), available phosphorus (AP), nitrate nitrogen (NN), urease (UE), β-glucosidase (BG) and protease (PRO) appeared the opposite tendency (P < 0.05). ② The stochastic process dominated the assembly process of reclaimed soil bacterial communities, with the diffusion limitation contributing the most. ③ Organic carbon, nitrate nitrogen, ammonium nitrogen, available phosphorus, β-glucosidase and catalase were significantly correlated with the abundances of carbon cycle functional genes. Reclamation activities have enhanced the carbon sequestration function through ameliorating the soil physicochemical properties. ④ According to the result equation model, the increase in reclamation years directly affects the physical and chemical properties of the soil, which in turn indirectly affects the assembly process of soil microbial communities, which may be the main reason for changes in the abundance of carbon cycling functional genes. The research results could provide theoretical basis for improving the reclaimed soil productivity and elevating carbon sequestration functions in mining areas

A novel strategy to prevent hydrogen charging via spontaneously molten-slag-covering droplet transfer mode in underwater wet FCAW

Underwater wet welding is widely used in offshore platform maintenance, oil pipeline repair and wreck salvage operations. A high diffusible hydrogen content is recognized as one of the critical reasons behind the reduction in the reliability of underwater wet welded joints. In this study, the entry route of hydrogen during underwater wet flux-cored arc welding of 304 stainless steel at a depth of 0.5 m was first confirmed experimentally using an in-situ X-ray imaging system. The hydrogen charging was deemed to dominantly occur when pendant droplets were formed due to the extremely high temperature of molten metal and the absence of slag coverage. This resulted in 13.51 mL/100 g of diffusible hydrogen remaining in the droplet and 9.42 mL/100 g in the deposited metal. To prevent hydrogen charging, an unprecedented molten-slag-covering droplet transfer mode was developed by reducing the CaF2 content and maintaining the CaF2/TiO2 to an appropriate ratio in the flux, through which the molten slag spontaneously covered the droplet, electric arc and molten pool completely during the entire welding process and the entry of hydrogen was successfully blocked and the diffusible hydrogen content was reduced to the same level as that achieved via onshore welding (3.26 mL/100 g)