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Fluctuating environments that consist of regular cycles of co-occurring stress are a common challenge faced by cellular populations. For a population to thrive in constantly changing conditions, an ability to coordinate a rapid cellular response is essential. Here, we identify a mutation conferring an arginine-to-histidine (Arg to His) substitution in the transcription terminator Rho. The rho R109H mutation frequently arose in Escherichia coli populations experimentally evolved under repeated long-term starvation conditions, during which the accumulation of metabolic waste followed by transfer into fresh media results in drastic environmental pH fluctuations associated with feast and famine. Metagenomic sequencing revealed that populations containing the rho mutation also possess putative loss-of-function mutations in ydcI, which encodes a recently characterized transcription factor associated with pH homeostasis. Genetic reconstructions of these mutations show that the rho allele confers plasticity via an alkaline-induced reduction of Rho function that, when found in tandem with a ΔydcI allele, leads to intracellular alkalization and genetic assimilation of Rho mutant function. We further identify Arg to His substitutions at analogous sites in rho alleles from species that regularly experience neutral to alkaline pH fluctuations in their environments. Our results suggest that Arg to His substitutions in Rho may serve to rapidly coordinate complex physiological responses through pH sensing and shed light on how cellular populations use environmental cues to coordinate rapid responses to complex, fluctuating environments.

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To delve into the growth and physiological adaptations exhibited by the economically vital black wolfberry (Lycium ruthenicum) upon inoculation with arbuscular mycorrhizal fungi (AMF) under varying levels of saline-alkaline stress A series of pot experiments were conducted in a gradient saline-alkaline environment (0, 200, 400 mM NaCl: NaHCO3 = 1:1). One-year-old cuttings of black wolfberry, inoculated with two AMF species-Funneliformis mosseae (Fm) and Rhizophagus intraradices (Ri)-served as the experimental material, enabling a comprehensive analysis of seedling biomass, chlorophyll content, antioxidant enzyme activities, and other crucial physiological parameters. This study demonstrated that both Fm and Ri could form a symbiotic relationship with the root of Lycium ruthenicum. Notably, Fm inoculation significantly bolstered the growth of the underground parts, while exhibiting a remarkable capacity to scavenge reactive oxygen species (ROS), thereby effectively mitigating membrane oxidative damage induced by stress. Additionally, Fm promoted the accumulation of abscisic acid (ABA) in both leaves and roots, facilitating the exclusion of excess sodium ions from cells. Ri Inoculation primarily contributed to an enhancement in the chlorophyll b (Chlb) content, vital for sustaining photosynthesis processes. Furthermore, Ri's ability to enhance phosphorus (P) absorption under stressful conditions ensured a steady influx of essential nutrients. These findings point to different strategies employed for Fm and Ri inoculation. To holistically assess the saline-alkaline tolerance of each treatment group, a membership function analysis was employed, ultimately ranking the salt tolerance as Fm > Ri > non-mycorrhizal (NM) control. This finding holds paramount importance for the screening of highly resilient Lycium ruthenicum strains and offers invaluable theoretical underpinnings and technical guidance for the remediation of saline-alkaline soils, fostering sustainable agricultural practices in challenging environments.

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Plant thioredoxins (TRXs) are involved in numerous metabolic and signalling pathways, such as light-dependent regulation of photosynthesis. The atypical TRX CDSP32, chloroplastic drought-induced stress protein of 32 kDa, includes two TRX-fold domains and participates in responses to oxidative stress as an electron donor to other thiol reductases. Here, we further characterised potato lines modified for CDSP32 expression to clarify the physiological roles of the TRX. Upon high salt treatments, modified lines displayed changes in the abundance and redox status of CDSP32 antioxidant partners, and exhibited sensitivity to combined saline-alkaline stress. In non-stressed plants overexpressing CDSP32, a lower abundance of photosystem II subunits and ATP-synthase γ subunit was noticed. The CDSP32 co-suppressed line showed altered chlorophyll a fluorescence induction and impaired regulation of the transthylakoid membrane potential during dark/light and light/dark transitions. These data, in agreement with the previously reported interaction between CDSP32 and ATP-synthase γ subunit, suggest that CDSP32 affects the redox regulation of ATP-synthase activity. Consistently, modelling of protein complex 3-D structure indicates that CDSP32 could constitute a suitable partner of ATP-synthase γ subunit. We discuss the roles of the TRX in the regulation of both photosynthetic activity and enzymatic antioxidant network in relation with environmental conditions.

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Soda saline-alkaline stress significantly impedes the rice grain filling process and ultimately impacts rice yield. Biochar has been shown to mitigate the negative impacts of saline-alkaline stress on plants. However, the exact mechanism by which biochar influences the rice grain-filling rate in soda saline-alkaline soil is still not fully understood. A two-year field experiment was conducted with two nitrogen fertilizer levels (0 and 225 kg ha-1) and five biochar application rates [0% (B0), 0.5% (B1), 1.5% (B2), 3.0% (B3), and 4.5% (B4) biochar, w/w]. The results demonstrated that biochar had a significant impact on reducing the Na+ concentration and Na+/K+ ratio in rice grown in soda saline-alkaline lands, while also improving its stress physiological conditions. B1, B2, B3, and B4 showed a notable increase in the average grain-filling rate by 5.76%, 6.59%, 9.80%, and 10.79%, respectively, compared to B0; the time to reach the maximum grain-filling rate and the maximum grain weight saw increases ranging from 6.02% to 12.47% and from 7.85% to 14.68%, respectively. Meanwhile, biochar, particularly when used in conjunction with nitrogen fertilizer, notably enhanced the activities of sucrose synthase (SuSase), ADPG pyrophosphorylase (AGPase), starch synthase (StSase), and starch branching enzyme (SBE) of rice grains in soda saline-alkaline lands. Furthermore, rice yield increased by 11.95-42.74% in the B1, B2, B3, and B4 treatments compared to the B0 treatment. These findings showed that biochar improves yield by regulating ionic balance, physiological indicators, starch synthesis key enzyme activities, and the grain-filling rate in soda saline-alkaline paddy fields.

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Microbe-driven ammonia nitrogen removal plays a crucial role in the nitrogen cycle and wastewater treatment. However, the rational methods and mechanisms for boosting nitrogen conversion through microbial domestication are still limited. Herein, a combined alkali-photocatalytic stimulation strategy was developed to activate the Halomonas shizuishanensis DWK9 for efficient ammonia nitrogen removal. The strain DWK9 selected from saline-alkaline soil in Northwestern China possessed strong resistance to stress of saline-alkaline environment and free radicals, and was abundant in nitrogen conversion genes, thus is an ideal model for advanced microbial domestication. Bacterial in the combined alkali-photocatalytic stimulation group achieved a high ammonia nitrogen conversion rate of 67.5 %, 10 times outperforming the non-stimulated and single alkali/photocatalytic stimulation control groups. Morphology analysis revealed that the bacteria in the alkali-photocatalytic stimulated group formed a favorable structure for bioelectric transfer. Remarkably, the domesticated bacteria demonstrated improved electrochemical properties, including increased current capacity and lower overpotentials and impedance. Prokaryotic transcription genetic analysis together with qPCR analysis showed upregulation of denitrification-related metabolic pathway genes. A novel FAD dependent and NAD(P)H independent energy mode has been proposed. The universality and effectiveness of the as-developed combined alkali-photocatalytic microbial domestication strategy were further validated through indicator fish survival experiments. This work provides unprecedented degrees of freedom for the exploration of rational microbial engineering for optimized and controllable biogeochemical conversion.

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Lilium pumilum DC (L. pumilum DC) plays an important role in the rational utilization of salinized soil. To explore the molecular mechanism of salt-tolerant L. pumilum, the LpMYB4 was cloned. LpMYB4 close relationship with Bambusa emeiensis and Zea mays MYB4 throughout the phylogenetic tree construction. LpMYB4 protein was found to be localized in the nucleus. Prokaryotic and eukaryotic bacterial solution resistance experiments proved that the exogenous introduction of LpMYB4 made the overexpression strains obtain better survival ability under saline-alkaline stress. Compared with wild-type plants, tobacco plants overexpressing LpMYB4 had better growth and lower leaf wilting and lodging, the content of chlorophyll was higher, the content of hydrogen peroxide and superoxide anion was lower, the activity of peroxidase and superoxide dismutase was higher and the relative conductivity was lower under saline-alkaline stress. The analysis of seed germination and seedling resistance of transgenic plants under salt stress showed that LpMYB4 transgenic seeds were more tolerant to salt stress during germination and growth. Yeast two-hybrid and two-luciferase complementation experiments showed that LpMYB4 interacted with yeast two-hybrid and LpGPX6. The analysis of the role of LpMYB4 in improving plant saline-alkali resistance is helpful to the transformation of plant germplasm resources and has great significance for agriculture and sustainable development.

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Soil salinization effects plant photosynthesis in a number of global ecosystems. In this study, photosynthetic and physiological parameters were used to elucidate the impacts of saline-alkaline stress on Cyperus esculentus L. (C. esculentus) seedling photosynthesis. The results demonstrate that salt stress, alkali stress and mixed salt and alkali stress treatments all have similar bell-shaped influences on photosynthesis. At low concentrations (0-100 mmol L-1), saline-alkaline stress promoted net photosynthetic rate, transpiration rate and water use efficiency in C. esculentus. However, as the treatments increased in intensity (100-200 mmol L-1), plant photosynthetic parameters began to decline. We interpreted this as the capacity of C. esculentus to improve osmoregulatory capacity in low saline-alkaline stress treatments by accumulating photosynthetic pigment, proline and malondialdehyde to counterbalance the induced stress - an adaptive mechanism that failed once concentrations reached a critical threshold (100 mmol L-1). Stomatal conductance, maximum photosynthetic rate and actual photosynthetic rate all decreased with increasing concentration of the stress treatments, and intercellular carbon dioxide showed a decreasing and then increasing trend. These results indicated that when the saline-alkaline stress concentrations were low, C. esculentus seedlings showed obvious adaptive ability, but when the concentration increased further, the physiological processes of C. esculentus seedlings were significantly affected, with an obvious decrease in photosynthetic efficiency. This study provides a new understanding of the photosynthetic adaptation strategies of C. esculentus seedlings to varying concentrations of saline-alkaline stress.

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Soil alkalization is an adverse factor limiting plant growth and yield. As a signaling molecule and secondary metabolite, γ-aminobutyric acid (GABA) responds rapidly to alkaline stress and enhances the alkaline resistance of plants. However, the molecular mechanisms by which the GABA pathway adapts to alkaline stress remain unclear. In this study, a transcription factor, MdNAC104 is identified, from the transcriptome of the alkaline-stressed roots of apple, which effectively reduces GABA levels and negatively regulates alkaline resistance. Nevertheless, applying exogenous GABA compensates the negative regulatory mechanism of overexpressed MdNAC104 on alkaline resistance. Further research confirms that MdNAC104 repressed the GABA biosynthetic gene MdGAD1/3 and the GABA transporter gene MdALMT13 by binding to their promoters. Here, MdGAD1/3 actively regulates alkaline resistance by increasing GABA synthesis, while MdALMT13 promotes GABA accumulation and efflux in roots, resulting in an improved resistance to alkaline stress. This subsequent assays reveal that MdSINA2 interacts with MdNAC104 and positively regulates root GABA content and alkaline resistance by ubiquitinating and degrading MdNAC104 via the 26S proteasome pathway. Thus, the study reveals the regulation of alkaline resistance and GABA homeostasis via the MdSINA2-MdNAC104-MdGAD1/3/MdALMT13 module in apple. These findings provide novel insight into the molecular mechanisms of alkaline resistance in plants.

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Investigating differences in resistance to alkaline stress among three willow species can provide a theoretical basis for planting willow in saline soils. Therefore we tested three willow species (Salix matsudana, Salix gordejevii and Salix linearistipularis), already known for their high stress tolerance, to alkaline stress environment at different pH values under hydroponics. Root and leaf dry weight, root water content, leaf water content, chlorophyll content, photosynthesis and chlorophyll fluorescence of three willow cuttings were monitored six times over 15 days under alkaline stress. With the increase in alkaline stress, the water retention capacity of leaves of the three species of willow cuttings was as follows: S. matsudana > S. gordejevii > S. linearistipularis and the water retention capacity of the root system was as follows: S. gordejevii > S. linearistipularis > S. matsudana. The chlorophyll content was significantly reduced, damage symptoms were apparent. The net photosynthetic rate (Pn), rate of transpiration (E), and stomatal conductance (Gs) of the leaves showed a general trend of decreasing, and the intercellular CO2 concentration (Ci) of S. matsudana and S. gordejevii first declined and then tended to level off, while the intercellular CO2 concentration of S. linearistipularis first declined and then increased. The quantum yield and energy allocation ratio of the leaf photosystem II (PSII) reaction centre changed significantly (φPo, Ψo and φEo were obviously suppressed and φDo was promoted). The photosystem II (PSII) reaction centre quantum performance index and driving force showed a clear downwards trend. Based on the results it can be concluded that alkaline stress tolerance of three willow was as follows: S. matsudana > S. gordejevii > S. linearistipularis. However, since the experiment was done on young seedlings, further study at saplings stage is required to revalidate the results.

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BACKGROUND: Enterococcus faecalis biofilm was frequently found on the failed treated root canal wall, which survived by resisting disinfectant during endodontic treatment.Many researches have been conducted to explore the mechanisms of persistence of this pathogen in unfavorable conditions. However, no comprehensive proteomics studies have been conducted to investigate stress response in Enterococcus faecalis caused by alkali and NaOCl. OBJECTIVE: Enterococcus faecalis (E.f) has been recognized as a main pathogen of refractory apical periodontitis, its ability to withstand environmental pressure is the key to grow in the environment of high alkaline and anti-bacterial drug that causes chronic infection in the root canal. This study aims to focus on the protein expression patterns of E.f biofilm under extreme pressure environment". METHODS: Enterococcus faecalis biofilm model was established in vitro. Liquid Chromatograph-Mass Spectrometer (LC-MS/MS)-based label free quantitative proteomics approach was applied to compare differential protein expression under different environmental pressures (pH 10 and 5% sodium hypochlorite (NaOCl)). And then qPCR and Parallel Reaction Monitoring Verification (PRM) were utilized to verify the consequence of proteomics. RESULTS: The number of taxa in this study was higher than those in previous studies, demonstrating the presence of a remarkable number of proteins in the groups of high alkaline and NaOCl. Proteins involved in ATP-binding cassette (ABC) transporter were significantly enriched in experimental samples. We identified a total of 15 highly expressed ABC transporters in the high alkaline environment pressure group, with 7 proteins greater than 1.5 times. CONCLUSIONS: This study revealed considerable changes in expression of proteins in E.f biofilm during resistance to environmental pressures. The findings enriched our understanding of association between the differential expression proteins and environmental pressures.

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Soil salinization-alkalization severely affects plant growth and crop yield worldwide, especially in the Songnen Plain of Northeast China. Saline-alkaline stress increases the pH around the plant roots, thereby limiting the absorption and transportation of nutrients and ions, such as iron (Fe). Fe is an essential micronutrient that plays important roles in many metabolic processes during plant growth and development, and it is acquired by the root cells via iron-regulated transporter1 (IRT1). However, the function of Oryza sativa IRT1 (OsIRT1) under soda saline-alkaline stress remains unknown. Therefore, in this study, we generated OsIRT1 mutant lines and OsIRT1-overexpressing lines in the background of the O. sativa Songjing2 cultivar to investigate the roles of OsIRT1 under soda saline-alkaline stress. The OsIRT1-overexpressing lines exhibited higher tolerance to saline-alkaline stress compared to the mutant lines during germination and seedling stages. Moreover, the expression of some saline-alkaline stress-related genes and Fe uptake and transport-related genes were altered. Furthermore, Fe and Zn contents were upregulated in the OsIRT1-overexpressing lines under saline-alkaline stress. Further analysis revealed that Fe and Zn supplementation increased the tolerance of O. sativa seedlings to saline-alkaline stress. Altogether, our results indicate that OsIRT1 plays a significant role in O. sativa by repairing the saline-alkaline stress-induced damage. Our findings provide novel insights into the role of OsIRT1 in O. sativa under soda saline-alkaline stress and suggest that OsIRT1 can serve as a potential target gene for the development of saline-alkaline stress-tolerant O. sativa plants.

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Cryptococcus neoformans is an opportunistic human fungal pathogen capable of surviving in a wide range of environments and hosts. It has been developed as a model organism to study fungal pathogenesis due to its fully sequenced haploid genome and optimized gene deletion and mutagenesis protocols. These methods have greatly aided in determining the relationship between Cryptococcus genotype and phenotype. Furthermore, the presence of congenic mata and matα strains associated with a defined sexual cycle has helped further understand cryptococcal biology. Several in vitro stress conditions have been optimized to closely mimic the stress that yeast encounter in the environment or within the infected host. These conditions have proven to be extremely useful in elucidating the role of several genes in allowing yeast to adapt and survive in hostile external environments. This chapter describes various in vitro stress conditions that could be used to test the sensitivity of different mutant strains, as well as the protocol for preparing them. We have also included a list of mutants that could be used as a positive control strain when testing the sensitivity of the desired strain to a specific stress.

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BACKGROUND: Soybean (Glycine max), a vital grain and oilseed crop, serves as a primary source of plant protein and oil. Soil salinization poses a significant threat to soybean planting, highlighting the urgency to improve soybean resilience and adaptability to saline stress. Melatonin, recently identified as a key plant growth regulator, plays crucial roles in plant growth, development, and responses to environmental stress. However, the potential of melatonin to mitigate alkali stress in soybeans and the underlying mechanisms remain unclear. RESULTS: This study investigated the effects of exogenous melatonin on the soybean cultivar Zhonghuang 13 under alkaline stress. We employed physiological, biochemical, transcriptomic, and metabolomic analyses throughout both vegetative and pod-filling growth stages. Our findings demonstrate that melatonin significantly counteracts the detrimental effects of alkaline stress on soybean plants, promoting plant growth, photosynthesis, and antioxidant capacity. Transcriptomic analysis during both growth stages under alkaline stress, with and without melatonin treatment, identified 2,834 and 549 differentially expressed genes, respectively. These genes may play a vital role in regulating plant adaptation to abiotic stress. Notably, analysis of phytohormone biosynthesis pathways revealed altered expression of key genes, particularly in the ARF (auxin response factor), AUX/IAA (auxin/indole-3-acetic acid), and GH3 (Gretchen Hagen 3) families, during the early stress response. Metabolomic analysis during the pod-filling stage identified highly expressed metabolites responding to melatonin application, such as uteolin-7-O-(2''-O-rhamnosyl)rutinoside and Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside, which helped alleviate the damage caused by alkali stress. Furthermore, we identified 183 differentially expressed transcription factors, potentially playing a critical role in regulating plant adaptation to abiotic stress. Among these, the gene SoyZH13_04G073701 is particularly noteworthy as it regulates the key differentially expressed metabolite, the terpene metabolite Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside. WGCNA analysis identified this gene (SoyZH13_04G073701) as a hub gene, positively regulating the crucial differentially expressed metabolite of terpenoids, Hederagenin-3-O-glucuronide-28-O-glucosyl(1,2)glucoside. Our findings provide novel insights into how exogenous melatonin alleviates alkali stress in soybeans at different reproductive stages. CONCLUSIONS: Integrating transcriptomic and metabolomic approaches, our study elucidates the mechanisms by which exogenous melatonin ameliorates the inhibitory effects of alkaline stress on soybean growth and development. This occurs through modulation of biosynthesis pathways for key compounds, including terpenes, flavonoids, and phenolics. Our findings provide initial mechanistic insights into how melatonin mitigates alkaline stress in soybeans, offering a foundation for molecular breeding strategies to enhance salt-alkali tolerance in this crop.

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BACKGROUND AND AIMS: The escalating issue of soil saline-alkalization poses a growing global challenge. Leymus chinensis is a perennial grass species commonly used in the establishment and renewal of artificial grasslands that is relatively tolerant of saline, alkaline, and drought conditions. Nonetheless, reduced seed setting rates limit its propagation, especially on alkali-degraded grassland. Inter-annual variations have an important effect on seed yield and germination under abiotic stress, and we therefore examined the effect of planting year on seed yield components of L. chinensis. METHODS: We grew transplanted L. chinensis seedlings in pots for two (Y2), three (Y3), or four (Y4) years and collected spikes for measurement of seed yield components, including spike length, seed setting rate, grain number per spike, and thousand seed weight. We then collected seeds produced by plants from different planting years and subjected them to alkaline stress (25 mM Na2CO3) for measurement of germination percentage and seedling growth. RESULTS: The seed setting rate of L. chinensis decreased with an increasing number of years in pot cultivation, but seed weight increased. Y2 plants had a higher seed setting rate and more grains per spike, whereas Y4 plants had a higher thousand seed weight. The effects of alkaline stress (25 mM Na2CO3) on seed germination were less pronounced for the heavier seeds produced by Y4 plants. Na2CO3 caused a 9.2% reduction in shoot length for seedlings derived from Y4 seeds but a 22.3% increase in shoot length for seedlings derived from Y3 seeds. CONCLUSIONS: Our findings demonstrate significant differences in seed yield components among three planting years of L. chinensis under pot cultivation in a finite space. Inter-annual variation in seed set may provide advantages to plants. Increased alkalinity tolerance of seed germination was observed for seeds produced in successive planting years.

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BACKGROUND: The yeast Komagataella phaffii has become a very popular host for heterologous protein expression, very often based on the use of the AOX1 promoter, which becomes activated when cells are grown with methanol as a carbon source. However, the use of methanol in industrial settings is not devoid of problems, and therefore, the search for alternative expression methods has become a priority in the last few years. RESULTS: We recently reported that moderate alkalinization of the medium triggers a fast and wide transcriptional response in K. phaffii. Here, we present the utilization of three alkaline pH-responsive promoters (pTSA1, pHSP12 and pPHO89) to drive the expression of a secreted phytase enzyme by simply shifting the pH of the medium to 8.0. These promoters offer a wide range of strengths, and the production of phytase could be modulated by adjusting the pH to specific values. The TSA1 and PHO89 promoters offered exquisite regulation, with virtually no enzyme production at acidic pH, while limitation of Pi in the medium further potentiated alkaline pH-driven phytase expression from the PHO89 promoter. An evolved strain based on this promoter was able to produce twice as much phytase as the reference pAOX1-based strain. Functional mapping of the TSA1 and HSP12 promoters suggests that both contain at least two alkaline pH-sensitive regulatory regions. CONCLUSIONS: Our work shows that the use of alkaline pH-regulatable promoters could be a useful alternative to methanol-based expression systems, offering advantages in terms of simplicity, safety and economy.

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Riboflavins are secreted under iron deficiency as a part of the iron acquisition Strategy I, mainly when the external pH is acidic. In plants growing under Fe-deficiency and alkaline conditions, riboflavins have been reported to accumulate inside the roots, with very low or negligible secretion. However, the fact that riboflavins may undergo hydrolysis under alkaline conditions has been so far disregarded. In this paper, we report the presence of riboflavin derivatives and products of their alkaline hydrolysis (lumichrome, lumiflavin and carboxymethylflavin) in nutrient solutions of Cucumis sativus plants grown under different iron regimes (soluble Fe-EDDHA in the nutrient solution, total absence of iron in the nutrient solution, or two different doses of FeSO4 supplied as a foliar spray), either cultivated in slightly acidic (pH 6) or alkaline (pH 8.8, 10 mM bicarbonate) nutrient solutions. The results show that root synthesis and exudation of riboflavins is controlled by shoot iron status, and that exuded riboflavins undergo hydrolysis, especially at alkaline pH, with lumichrome being the main product of hydrolysis.

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Saline and alkaline stress is one of the major abiotic stresses facing agricultural production, which severely inhibits the growth and yield of plant. The application of plant growth regulators can effectively prevent crop yield reduction caused by saline and alkaline stress. Exogenous melatonin (MT) can act as a signaling molecule involved in the regulation of a variety of physiological processes in plants, has been found to play a key role in enhancing the improvement of plant tolerance to abiotic stresses. However, the effects of exogenous MT on saline and alkaline tolerance of table grape seedlings and its mechanism have not been clarified. The aim of this study was to investigate the role of exogenous MT on morphological and physiological growth of table grape seedlings (Vitis vinifera L.) under saline and alkaline stress. The results showed that saline and alkaline stress resulted in yellowing and wilting of grape leaves and a decrease in chlorophyll content, whereas the application of exogenous MT alleviated the degradation of chlorophyll in grape seedling leaves caused by saline and alkaline stress and promoted the accumulation of soluble sugars and proline content. In addition, exogenous MT increased the activity of antioxidant enzymes, which resulted in the scavenging of reactive oxygen species (ROS) generated by saline and alkaline stress. In conclusion, exogenous MT was involved in the tolerance of grape seedlings to saline and alkaline stress, and enhanced the saline and alkaline resistance of grape seedlings to promote the growth and development of the grape industry in saline and alkaline areas.

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Recent studies have demonstrated the crucial role of Cytochrome P450 enzymes (CYPs) in the production of secondary metabolites, phytohormones and antioxidants in plants. However, their functional characterization specifically under alkaline stress remains elusive. CYP82C4 was the key gene screened from a family of wild soybean CYPs in our previous studies. The aim of this present study was to clone the Glycine soja GsCYP82C4 gene and characterize its functions in Arabidopsis and Glycine max. The results showed that the GsCYP82C4 gene displayed a high expression in different plant tissues at mature stages compared to young stages. Further, higher temporal expression of the GsCYP82C4 gene was noted at 6, 12 and 24 h time points after alkali treatment in leaves compared to roots. In addition, overexpression of GsCYP82C4 improved alkaline stress tolerance in Arabidopsis via increased root lengths and fresh biomass and strengthened the antioxidant defense system via a reduction in superoxide radicals in transgenic lines compared to wild type (WT) and atcyp82c4 mutants. Further, the expression levels of stress-related marker genes were up-regulated in GsCYP82C4 OX lines under alkali stress. The functional analysis of GsCYP82C4 overexpression in soybean displayed better hairy root growth, increased fresh weight, higher antioxidant enzyme activities and reduced lipid peroxidation rates in OX lines compared to the soybean WT (K599) line. In total, our study displayed positive roles of GsCYP82C4 overexpression in both Arabidopsis and Glycine max to alleviate alkaline stress via altering expression abundance of stress responsive genes, stronger roots, higher antioxidant enzyme activities as well as reduced rates of lipid peroxidation and superoxide radicals.

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Fluctuating environments that consist of regular cycles of co-occurring stress are a common challenge faced by cellular populations. For a population to thrive in constantly changing conditions, an ability to coordinate a rapid cellular response is essential. Here, we identify a mutation conferring an arginine-to-histidine (Arg to His) substitution in the transcription terminator Rho. The rho R109H mutation frequently arose in E. coli populations experimentally evolved under repeated long-term starvation conditions, during which feast and famine result in drastic environmental pH fluctuations. Metagenomic sequencing revealed that populations containing the rho mutation also possess putative loss-of-function mutations in ydcI, which encodes a recently characterized transcription factor associated with pH homeostasis. Genetic reconstructions of these mutations show that the rho allele confers a plastic alkaline-induced reduction of Rho function that, when found in tandem with a ΔydcI allele, leads to intracellular alkalinization and genetic assimilation of Rho mutant function. We further identify Arg to His substitutions at analogous sites in rho alleles from species originating from fluctuating alkaline environments. Our results suggest that Arg to His substitutions in global regulators of gene expression can serve to rapidly coordinate complex responses through pH sensing and shed light on how cellular populations across the tree of life use environmental cues to coordinate rapid responses to complex, fluctuating environments.

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Rice production is seriously affected by saline-alkaline stress worldwide. To elucidate the saline-alkaline tolerance mechanisms in a novel tolerant rice variety, Shwe Nang Gyi (SNG), we investigated ion accumulation in SNG and Koshihikari (KSH), which is a saline-alkaline sensitive rice variety, and the candidates for saline-alkaline inducible genes in SNG using RNA-seq. SNG had superior ion accumulation capacity, such as K and Zn, compared to KSH. In contrast, SNG accumulated the same level of Na content in its leaf blades as KSH despite the higher dry weight of the SNG leaf blades. We further found that the expression of numerous genes, including several K+ transporter/high-affinity K+ transporter/K+ uptake protein/K+ transporter (HAK/KUP/KT) family members, were upregulated in SNG, and that OsHAK17 and OsHAK21 expression levels in the roots were significantly higher in SNG than in KSH. Moreover, yeast complementation analysis revealed that OsHAK17 was involved in K+ uptake under high-Na conditions. These results suggested that SNG has an effective K+ acquisition system supported by OsHAK17 functioning in saline-alkaline environments.

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