Salt Tolerance in Astragalus cicer Microsymbionts: The Role of Glycine Betaine in Osmoprotection

Characterization of drought stress-mitigating Rhizobium from faba bean (Vicia faba L.) in the Chinese Qinghai-Tibet Plateau

Rhizobium-driven symbiotic nitrogen-fixation in legumes not only benefits the growth but also enhances the stress tolerance of plants. Isolating and characterizing efficient, drought-tolerant rhizobia is a central goal for improving crop yields in arid regions. Here, we phylogenetically and biochemically characterized a novel strain of Rhizobium ('QHCD11') sampled from the root nodules of faba beans growing in an arid agricultural area in Qinghai-Tibet. We further tested the drought tolerance of the strain as well as of 'Qingcan 14' faba bean seedlings inoculated with it. Biochemical characterization involved bromothymol blue (BTB) tests, carbon metabolic profiling (Biolog GENIII), DNA-DNA hybridization (dDDH) assays, average nucleotide identity (ANI) analyses, and 16S rRNA sequencing. The result indicated that strain 'QHCD11' likely belongs to the Rhizobium indicum species. Drought stress tolerance was assessed by exposure to polyethylene glycol (PEG-6000) at concentrations of 0, 10, 15, and 20%. Increasing concentrations of PEG-6000 tended to result in decreased growth of 'QHCD11', although the strain performed better at 20% PEG 6000 than at 15%. Inoculation of drought-stressed faba bean seedlings with strain 'QHCD11' improved root vitality, chlorophyll content, antioxidant enzyme activities, and plant height. We suggest that inoculation of faba beans with 'QHCD11' is an environmentally sound strategy for mitigating crop drought stress in arid and semi-arid regions. In addition, the results presents here will benefit future studies into faba bean-rhizobia symbioses under drought stress.

Impact of natural betaine supplementation on rumen fermentation and productive performance of lactating Damascus goats

Two natural betaine sources; dehydrated condensed molasses fermentation solubles (Bet1) and Betafin®, a commercial anhydrous betaine extracted from sugar beet molasses and vinasses (Bet2); were used to investigate their impact on rumen fermentation parameters and lactation performance of lactating goats. Thirty-three lactating Damascus goats, with an average weight of 37 ± 0.7 kg and their age ranged from 22 to 30 months (2^nd and 3^rd lactation season), were divided into three groups, each group contained 11 animals. The control group (CON) was fed ration without betaine. While the other experimental groups were fed a control ration supplemented either with Bet1 or Bet2 to provide a 4 g betaine/kg diet. Results confirmed that betaine supplementation improved nutrient digestibility and nutritive value, and increased milk production and milk fat contents with both Bet1 and Bet2. Significant increases in concentration of ruminal acetate were observed in betaine-supplemented groups. Goats fed dietary betaine non-significantly recorded higher concentrations of short and medium-chain fatty acids (C4:0 to C12:0), and significant lower concentrations of C14:0 and C16:0 in milk. Also, both Bet1 and Bet2 non-significantly decreased the blood concentrations of cholesterol and triglycerides. Therefore, it could be concluded that betaine can improve the lactation performance of lactating goats and produce healthy milk with beneficial characteristics.

Valorization of food waste fermentation liquid into single cell protein by photosynthetic bacteria via stimulating carbon metabolic pathway and environmental behaviour

Single cell protein (SCP) production by photosynthetic bacteria (PSB) is dependent on the bioavailability of carbon source, while sufficient volatile fatty acids (VFAs) in food waste fermentation liquid might be a potential alternative. It is unclear how the fermentation liquid affects the SCP biosynthesis and the related metabolic mechanism. This work demonstrated that the SCP production could be improved effectively (2088.4 mg/L) with high conversion capacity of carbon source (0.99 mg-biomass/mg-COD) by regulating carbon source level. PSB preferred to utilize the VFAs in food waste fermentation liquid. The carbon metabolic pathways (e.g., the transformation of VFAs to acetyl-CoA, and tricarboxylic acid cycle) involved in the SCP production were enhanced under optimal condition. Moreover, optimal carbon source regulation could significantly stimulate the environmental behaviour of PSB (e.g., two-component system, quorum sensing, and ATP-binding cassette transporter) involved in adaptation to external stimulus and maintaining high bacterial activity, resulting in SCP yield promotion.

Integrative Analysis of the Transcriptome and Metabolome Reveals the Mechanism of Saline–Alkali Stress Tolerance in Astragalus membranaceus (Fisch) Bge. var. mongholicus (Bge.) Hsiao

Saline–alkali stress is a major abiotic stress affecting the quality and yield of crops. Astragalus membranaceus (Fisch) Bge. var. mongholicus (Bge.) Hsiao (A. mongholicus) is a well-known medicine food homology species with various pharmacological effects and health benefits that can grow well in saline–alkali soil. However, the molecular mechanisms underlying the adaptation of A. mongholicus plants to saline–alkali stress have not yet been clarified. Here, A. mongholicus plants were exposed to long-term saline–alkali stress (200 mmol·L -1 mixed saline–alkali solution), which limited the growth of A. mongholicus. The roots of A. mongholicus could resist long-term saline–alkali stress by increasing the activity of antioxidant enzymes and the content of osmolytes. Transcriptome analysis (via the Illumina platform) and metabolome analysis (via the Nexera UPLC Series QE Liquid Mass Coupling System) revealed that saline–alkali stress altered the activity of various metabolic pathways (e.g., amino acid metabolism, carbohydrate metabolism, lipid metabolism, and biosynthesis of other secondary metabolites). A total of 3,690 differentially expressed genes (DEGs) and 997 differentially accumulated metabolites (DAMs) were identified in A. mongholicus roots under saline–alkali stress, and flavonoid-related DEGs and DAMs were significantly up-regulated. Pearson correlation analysis revealed significant correlations between DEGs and DAMs related to flavonoid metabolism. MYB transcription factors might also contribute to the regulation of flavonoid biosynthesis. Overall, the results indicate that A. mongholicus plants adapt to saline–alkali stress by up-regulating the biosynthesis of flavonoids, which enhances the medicinal value of A. mongholicus.

The application of glycine betaine to alleviate the inhibitory effect of salinity on one-stage partial nitritation/anammox process

One-stage partial nitritation/anammox (PN/A) has been proposed as a sustainable method for removing nitrogen from various wastewater. However, the activities of ammonium-oxidizing bacteria (AOB) and anammox bacteria are often inhibited by the exposure to salinity, thereby hindering their wide application in treating industrial wastewater with high salinity. This study reports that the addition of glycine betaine (GB), which is a compatible solute, could alleviate the inhibitory effects of salinity on both AOB and anammox, thereby improving nitrogen removal performance in a one-stage PN/A system. Short-term tests showed that with an addition of GB higher than 1 mM, the activity of AOB and anammox under salinity of 30 g/L could be increased by at least 45% and 51%, respectively. The half-inhibitory concentration of AOB and anammox rose with increasing GB concentration, with 1 mM GB being the optimal cost-effective dosage. Long-term experiments also demonstrated that 1 mM GB addition could enhance nitrogen removal performance and shorten recovery time by 42.9% under a salinity stress of 30 g/L. Collectively, GB addition was found to be a feasible and effective strategy to the counteract adverse effects of salinity on PN/A process. PRACTITIONER POINTS: Glycine betaine (GB) could improving performance of the PN/A process by alleviating the inhibitory effects of salinity on both AOB and anammox bacteria. A GB concentration of 1 mM was found to be optimum in terms of effectiveness and cost. GB addition was a feasible and effective strategy to remain stabilized in the community structure of PN/A sludge. GB could optimize the nitrogen removal performance and shorten the recovery time of PN/A process under saline stress.

Betaine Supplementation Improves the Production Performance, Rumen Fermentation, and Antioxidant Profile of Dairy Cows in Heat Stress

The aim of the current research was to investigate the effects of betaine (Bet) supplementation on the production performance, rumen fermentation, digestibility, and serum indexes of dairy cows. Thirty healthy Holstein cows with the same parity (milk production = 22 ± 2.5 kg) were randomly selected and divided into three groups. One group served as a control group (CON; no betaine); the other two groups were Bet1 (15 g/d per cow) and Bet2 (30 g/d per cow). All cows were fed regularly three times a day at 06:00, 14:00, and 22:00 h. Cows received the formulate diet, and water was provided ad libitum. The experiment lasted for 60 days during the summer season. Results showed that the dry matter intake, milk protein, and fat of Bet1 cows was significantly higher (p < 0.05) than that in other groups. The content of volatile fatty acid (VFA) in Bet1 was significantly higher (p < 0.05) than CON. Consistent with VFA, a similar trend was found in acetate, while propionate exhibited an opposite trend. Compared to other groups, the microbial protein (MCP) concentrations of Bet1 increased (p < 0.05). The apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) of Bet1 was significantly higher (p < 0.05) than CON. The serum concentration of total antioxygenic capacity (T-AOC) in Bet1 and Bet2 was significantly increased (p < 0.05). Furthermore, the contents of malonaldehyde (MDA) and superoxide dismutase (SOD) in Bet2 were higher (p < 0.05) than that in other groups. Compared to CON and Bet2, Bet1 significantly increased (p < 0.05) the serum concentrations of glucose. Therefore, it is practicable to feed betaine to lactating cows to improve their performance in heat stress.

Betaine Improves Milk Yield in Grazing Dairy Cows Supplemented with Concentrates at High Temperatures

Simple Summary

Heat events during summer can result in dramatic reductions in milk production in grazing dairy cows as they attempt to reduce their accumulated heat load. Therefore, there is interest in dietary manipulations that can decrease heat production or increase heat dissipation. One of the actions of sugar beet-derived betaine is to act as an osmolyte and reduce intracellular ion pumping and heat production. Therefore, this study was conducted to investigate the effects of dietary betaine supplementation on milk and milk component production in grazing dairy cows during hot periods in summer.

Abstract

Betaine is an organic osmolyte sourced from sugar beet that accumulates in plant cells undergoing osmotic stress. Since the accumulation of betaine lowers the energy requirements of animals and, therefore, metabolic heat production, the aim of this experiment was to investigate if betaine supplementation improved milk yield in grazing dairy cows in summer. One hundred and eighteen Friesian × Holstein cows were paired on days in milk and, within each pair, randomly allocated to a containing treatment of either 0 or 2 g/kg natural betaine in their concentrate ration for approximately 3 weeks during February/March 2015 (summer in Australia). The mean maximum February temperature was 30 °C. Cows were allocated approximately 14 kg dry matter pasture and 7.5 kg of concentrate pellets (fed in the milking shed) per cow per day and were milked through an automatic milking system three times per day. Betaine supplementation increased average daily milk yield by over 6% (22.0 vs. 23.4 kg/day, p < 0.001) with the response increasing as the study progressed as indicated by the interaction (p < 0.001) between betaine and day. Milk fat % (p = 0.87), milk protein % (p = 0.90), and milk somatic cell count (p = 0.81) were unchanged by dietary betaine. However, betaine supplementation increased milk protein yield (677 vs. 719 g/day, p < 0.001) and fat yield (874 vs. 922 g/day, p < 0.001) with responses again being more pronounced as the study progressed. In conclusion, dietary betaine supplementation increased milk and component yield during summer in grazing dairy cows.

High Salt Tolerance of a Bradyrhizobium Strain and Its Promotion of the Growth of Stylosanthes guianensis

Salinity is a serious limiting factor for the growth of rhizobia. Some rhizobia are tolerant to salt stress and promote plant growth, but the mechanisms underlying these effects are poorly characterized. The growth responses and osmoprotectants in four Bradyrhizobium strains were examined under salt stress in this study. Two-dimensional electrophoresis (2-DE) and mass spectrometry were conducted to investigate protein profiles in rhizobia exposed to salt stress. Subsequently, salt tolerance in stylo (Stylosanthesguianensis) inoculated with rhizobia was further detected in hydroponics. Results showed that the Bradyrhizobium strain RJS9-2 exhibited higher salt tolerance than the other three Bradyrhizobium strains. RJS9-2 was able to grow at 0.35 M NaCl treatment, while the other three Bradyrhizobium strains did not grow at 0.1 M NaCl treatment. Salt stress induced IAA production, and accumulation of proline, betaine, ectoine, and trehalose was observed in RJS9-2 but not in PN13-1. Proteomics analysis identified 14 proteins regulated by salt stress in RJS9-2 that were mainly related to the ABC transporter, stress response, and protein metabolism. Furthermore, under saline conditions, the nodule number, plant dry weight, and N concentration in stylo plants inoculated with RJS9-2 were higher than those in plants inoculated with PN13-1. These results suggest that the tolerance of RJS9-2 to salt stress may be achieved by the coordination of indole-3-acetic acid (IAA) production, osmoprotectant accumulation, and protein expression, thus promoting stylo growth.

Evaluation of dietary betaine in lactating Holstein cows subjected to heat stress

Betaine (BET), a natural, organic osmolyte, improves cellular efficiency by acting as a chaperone, refolding denatured proteins. To test if dietary BET reduced the effect of heat stress (HS) in lactating dairy cows, multiparous, lactating Holstein cows (n=24) were blocked by days in milk (101.4±8.6 d) and randomly assigned to 1 of 3 daily intakes of dietary BET: the control (CON) group received no BET, mid intake (MID) received 57mg of BET/kg of body weight, and high dose (HI) received 114mg of BET/kg of body weight. Cows were fed twice daily and BET was top-dressed at each feeding. Cows were milked 2 times/d and milk samples were taken daily for analysis. Milk components, yield, feed intake, and water intake records were taken daily. Rectal temperature and respiration rate were taken 3 times/d at 0600, 1400, and 1800h. Cows were housed in environmentally controlled rooms and were allowed acclimation for 7d at thermoneutral (TN) conditions with a mean temperature-humidity index of 56.6. Cows were then exposed to 7d of TN followed by 7d of HS represented by a temperature-humidity index of 71.5 for 14d. This was followed by a recovery period of 3d at TN. Dietary BET increased milk yield during the TN period. No differences were found between BET and CON in total milk production or milk composition during HS. The increase in water intake during HS was not as great for cows fed BET compared with controls. The cows on CON diets had higher p.m. respiration rate than both MID and HI BET during HS, but lower rectal temperature compared with BET. No difference was found in serum glucose during TN, but cows given HI had elevated glucose levels during HS compared with CON. No differences were found in serum insulin levels between CON and BET but an intake by environment interaction was present with insulin increasing in HI-treated lactating dairy cows during HS. The heat shock response [heat shock protein (HSP) 27 and HSP70] was upregulated in bovine mammary epithelial cells in vitro. Blood leukocyte HSP27 was downregulated at the HI dose under TN conditions and HSP70 was upregulated at the HI dose and this effect was increased by HS. No effect was seen with the MID dose with HSP27 or HSP70. The lack of effect of BET at MID may be associated with uptake across the gut. We conclude that BET increased milk production under TN conditions and was associated with reduced feed and water intake and slightly increased body temperatures during HS of cows fed BET. The effect of BET on milk production was lost during HS with HI BET, whereas serum glucose levels increased during HS.

Simultaneous determination of six active metabolites in Astragalus mongholicus (Fisch.) Bge. under salt stress by ultra-pressure liquid chromatography with tandem mass spectrometry

Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao (A. mongholicus, family Leguminosae) is one of the most important traditional Chinese herbs because it contains lots of bioactive metabolites, which have beneficial and pharmacological effects on health. Simultaneously, it has been proved to be a salt-tolerant plant-one of the potential species to control the soil salinization. Therefore, a sensitive and specific ultra-pressure liquid chromatography coupled with tandem mass spectrometric (UPLC-MS/MS) method was developed and validated for the simultaneous determination of six main bioactive metabolites, astragaloside IV, cycloastragenol, calycosin-7-O-β-d-glucoside, calycosin, ononin and formononetin in different organs of A. mongholicus. The detection was accomplished by multiple-reaction monitoring (MRM) scanning via electrospray ionization source operating in the positive ionization mode. Calibration curves offered linear ranges of two orders of magnitude with R(2) > 0.99. The method was fully validated for the linearity, intra-day and inter day precisions, accuracy, recovery, matrix effect and stability. Then this method was successfully applied to detect the content of major bioactive metabolites in different plant organs of A. mongholicus under salt stress. Significant variations in the content of six bioactive metabolites were observed after been processed by different levels of salinity in different part of plant. The results support for further exploration of the salt-tolerant mechanisms in A. mongholicus and its possibility as the species that control the soil salinization. Meanwhile, we established a UPLC-MS/MS assay of the trace components in seedling of A. mongholicus in this study.