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The overlapping regulation and effects of various stress response pathways in bacteria have been a major subject of study for several decades. This work examines the mechanisms by which a laboratory-acquired mutation in the rpoB gene conferring antibiotic tolerance also improves salt tolerance in Escherichia coli , an important pathogen of the human gut. We demonstrate that the rpoB mutation mimics the effects of multiple stress response pathways on gene expression and that pre-activation of these responses is critical for conferring hyperosmotic shock tolerance. These findings significantly advance our understanding of the genetic mechanisms controlling salt tolerance in bacteria and implicate the stringent response as one factor capable of conferring salt tolerance independent of the general stress response. Furthermore, these findings highlight the intricate connections between salt tolerance and other stress response pathways.

Euryhaline species exhibit significant adaptability to different salinities. This study elucidates how a single-celled euryhaline eukaryote navigates both transient and sustained salinity shifts at the molecular level. Comparative genomic analysis revealed that this organism expanded 195 gene families involved in ion transport and stress response. Transcriptomic analysis revealed distinct molecular foundations that underpin its transient and sustained adaptation to salinity stress. For high salinity, it transiently activates membrane transport systems, while long-term adaptation focuses on reprogramming metabolism to optimize energy use. In response to low salinity, the short-term response involves hydrolyzing intracellular materials, followed by the long-term activation of protective mechanisms. Additionally, alternative splicing fine-tunes genes involved in signaling and transport. These findings reveal unique genetic and cellular adaptation to salinity fluctuations in unicellular eukaryotes and establish a valuable resource for future functional investigations.

Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

Abstract Soil salinization, affecting 6.5% of arable land, deteriorates soil properties, reduces microbiota activity, hinders plant growth, and accelerates soil erosion. Excessive salt induces physiological drought and toxicity stress in plants, causing chlorosis, ion imbalances, and enzyme disruptions. This paper discusses microorganisms’ resistance mechanisms, plant responses to salt stress, and summarizes current knowledge on bacterial osmoprotectants and their functions. It also reviews emerging agrobiotechnological strategies using microbial osmoprotectants to remediate salinized soils and enhance plant growth and productivity under salt stress. Osmoprotectants stabilize proteins, buffer redox potential, and retain water, thus alleviating osmotic stress and promoting bacteria and plants growth. Their application improves soil properties by enhancing aggregate formation, water permeability, moisture content, cation exchange capacity, and ion availability. Despite extensive literature on the function of osmoprotectants, the knowledge about their role in soil environments and agrobiotechnology applications remains limited. This paper indicates proposed research perspectives, including discovering new osmoprotectants, their correlation with soil fertilization, interactions with the soil microbiome, and plant responses. It also identifies significant knowledge gaps in these areas, highlighting the need for further studies to consolidate existing data and assess the potential of this approach to enhance soil health and crop productivity in saline environments. This review explores microbial osmoprotectants as innovative agrobiotechnological tools to combat soil salinization, emphasizing their potential to improve soil health, enhance plant resilience, and address critical challenges in sustainable agriculture under salt stress.

Salinization of inland waters is a growing concern due to climate change and human activities. Understanding how organisms adapt to saline environments is vital. Tetrahymena thermophila , a model organism, was studied to explore its adaptation mechanisms. The findings show that through gene regulation, it can acclimate to high salt conditions. The role of mitochondria in metabolic reprogramming during this process is significant. This research contributes to a more profound understanding of how organisms adapt to saline stress and the molecular mechanisms underlying such adaptations, which may aid in predicting and managing the impacts of salinization on aquatic ecosystems.

Plants have established different mechanisms to cope with environmental fluctuations and accordingly fine‐tune their growth and development through the regulation of complex molecular networks. It is largely unknown how the network architectures change and what the key regulators in stress responses and plant growth are. Here, we investigated a complex, highly interconnected network of 20 Arabidopsis transcription factors (TFs) at the basis of leaf growth inhibition upon mild osmotic stress. We tracked the dynamic behavior of the stress‐responsive TFs over time, showing the rapid induction following stress treatment, specifically in growing leaves. The connections between the TFs were uncovered using inducible overexpression lines and were validated with transient expression assays. This study resulted in the identification of a core network, composed of ERF6, ERF8, ERF9, ERF59, and ERF98, which is responsible for most transcriptional connections. The analyses highlight the biological function of this core network in environmental adaptation and its redundancy. Finally, a phenotypic analysis of loss‐of‐function and gain‐of‐function lines of the transcription factors established multiple connections between the stress‐responsive network and leaf growth. Synopsis This study unravels a transcriptional network controlling Arabidopsis leaf growth inhibition in response to osmotic stress. The network consists of 20 transcription factors, whose complex and redundant patterns of interconnections enable robust adaptation to environmental changes. Linear pathways are a simplification. Multiple transcription factors can regulate the same target genes and, in some cases more than one transcription factor is necessary to induce the expression of a target gene. The network is robust because regulatory redundancy is built in, making the network less susceptible to mutations. ERF6 and ERF98 are both induced in the first induction group and can transcriptionally activate a large part of the network. They have an overlap of 6 target genes. ERF8 and ERF9 are both induced in the third induction group and can transcriptionally repress a large part of the network, showing an overlap of 9 target genes. The network is efficient for environmental adaption to a stress signal. The repressing activities in the network after 2 h of stress enables the network to return to its prestimulus state. The network is highly responsive to a range of input signals and might be part of a general stress response. However, the need for two transcription factors to transactivate target genes prevents stochastic activation of the network. The random induction of the network would lead to a needless stress response which is disadvantageous for the plant. Graphical Abstract This study unravels a transcriptional network controlling Arabidopsis leaf growth inhibition in response to osmotic stress. The network consists of 20 transcription factors, whose complex and redundant patterns of interconnections enable robust adaptation to environmental changes.

The ability of plant growth promoting rhizobacteria (PGPR) for imparting abiotic stress tolerance to plants has been widely explored in recent years; however, the diversity and potential of these microbes have not been maximally exploited. In this study, we characterized four bacterial strains, namely, Pseudomonas aeruginosa PM389, Pseudomonas aeruginosa ZNP1, Bacillus endophyticus J13 and Bacillus tequilensis J12, for potential plant growth promoting (PGP) traits under osmotic-stress, induced by 25% polyethylene glycol (PEG) in the growth medium. Growth curve analysis was performed in LB medium with or without PEG, in order to understand the growth patterns of these bacteria under osmotic-stress. All strains were able to grow and proliferate under osmotic-stress, although their growth rate was slower than that under non-stressed conditions (LB without PEG). Bacterial secretions were analyzed for the presence of exopolysaccharides and phytohormones and it was observed that all four strains released these compounds into the media, both, under stressed and non-stressed conditions. In the Pseudomonas strains, osmotic stress caused a decrease in the levels of auxin (IAA) and cytokinin (tZ), but an increase in the levels of gibberellic acid. The Bacillus strains on the other hand showed a stress-induced increase in the levels of all three phytohormones. P. aeruginosa ZNP1 and B. endophyticus J13 exhibited increased EPS production under osmotic-stress. While osmotic stress caused a decrease in the levels of EPS in P. aeruginosa PM389, B. tequilensis J12 showed no change in EPS quantities released into the media under osmotic stress when compared to non-stressed conditions. Upon inoculating Arabidopsis thaliana seedlings with these strains individually, it was observed that all four strains were able to ameliorate the adverse effects of osmotic-stress (induced by 25% PEG in MS-Agar medium) in the plants, as evidenced by their enhanced fresh weight, dry weight and plant water content, as opposed to osmotic-stressed, non-inoculated plants.

Summary Complex RNA transcription and processing produces a diverse range catalog of long noncoding RNAs (lncRNAs), important biological regulators that have been implicated in osmotic stress responses in plants. Promoter upstream transcript (PROMPT) lncRNAs share some regulatory elements with the promoters of their neighbouring protein‐coding genes. However, their function remains unknown. Here, using strand‐specific RNA sequencing, we identified 209 differentially regulated osmotic‐responsive PROMPTs in poplar (Populus simonii). PROMPTs are transcribed bidirectionally and are more stable than other lncRNAs. Co‐expression analysis of PROMPTs and protein‐coding genes divided the regulatory network into five independent subnetworks including 27 network modules. Significantly enriched PROMPTs in the network were selected to validate their regulatory roles. We used delaminated layered double hydroxide lactate nanosheets (LDH‐lactate‐NS) to transport synthetic nucleic acids into live tissues to mimic overexpression and interference of a specific PROMPT. The altered expression of PROMPT_1281 induced the expression of its cis and trans targets, and this interaction was governed by its secondary structure rather than just its primary sequence. Based on this example, we proposed a model that a concentration gradient of PROMPT_1281 is established, which increases the probability of its interaction with targets near its transcription site that shares common motifs. Our results firstly demonstrated that PROMPT_1281 act as carriers of MYB transcription factors to induce the expression of target genes under osmotic stress. In sum, our study identified and validated a set of poplar PROMPTs that likely have regulatory functions in osmotic responses.

In a wake of shifting climatic scenarios, plants are frequently forced to undergo a spectrum of abiotic and biotic stresses at various stages of growth, many of which have a detrimental effect on production and survival. Naturally, microbial consortia partner up to boost plant growth and constitute a diversified ecosystem against abiotic stresses. Despite this, little is known pertaining to the interplay between endophytic microbes which release phytohormones and stimulate plant development in stressed environments. In a lab study, we demonstrated that an endophyte isolated from the Kargil region of India, a Fusarium equiseti strain K23-FE, colonizes the maize hybrid MAH 14 − 5, promoting its growth and conferring polyethylene glycol (PEG)-induced osmotic stress tolerance. To unravel the molecular mechanism, maize seedlings inoculated with endophyte were subjected to comparative transcriptomic analysis. In response to osmotic stress, genes associated with metabolic, photosynthesis, secondary metabolites, and terpene biosynthesis pathways were highly upregulated in endophyte enriched maize seedlings. Further, in a greenhouse experiment, maize plants inoculated with fungal endophyte showed higher relative leaf water content, chlorophyll content, and antioxidant enzyme activity such as polyphenol oxidase (PPO) and catalase (CAT) under 50% field capacity conditions. Osmoprotectant like proline were higher and malondialdehyde content was reduced in colonized plants. This study set as proof of concept to demonstrate that endophytes adapted to adverse environments can efficiently tweak non-host plant responses to abiotic stresses such as water deficit stress via physiological and molecular pathways, offering a huge opportunity for their deployment in sustainable agriculture. Graphical Abstract Key message Discovering the molecular mechanism underlying Fusarium equiseti strain K23-FE enhances maize resilience to osmotic stress and illuminates promising avenues for sustainable agricultural practices amidst shifting climatic challenges.

Present communication reports laboratory and pot experiments conducted to study the influence of water and osmotic stress on nitrogen uptake and metabolism in two wheat ( Triticum aestivum L) cultivars with and without potassium supplementation. Polyethylene glycol 6000-induced osmotic stress/restricted irrigation caused a considerable decline in the activity of nitrate reductase, glutamate synthase, alanine and aspartate aminotransferases, and glutamate dehydrogenase. Potassium considerably improved nitrogen metabolism under normal water supply conditions and also resulted in amelioration of the negative impact of water and osmotic stresses indicating that potassium supplementation can be used as a potential tool for enhancing the nitrogen use efficiency in wheat for exploiting its genetic potential.