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Phytohormone-like plant growth regulators are becoming hallmarks in plant stress biology since they can offer incredible benefits to plants, such as increased crop output, improved growth features and stress tolerance. Among them polyamines (PAs) such as putrescine (Put), spermidine (Spd), and spermine (Spm), are recognized as important bio-stimulants that can boost plant growth, productivity, and stress tolerance, whether provided exogenously or synthesized endogenously by genetically engineered plants. However, the precise mechanism by which they regulate plant development and stress responses and their interactions with other signaling molecules remains unknown. Hence, unravelling the molecular complexity of PAs signaling in plants can help us to improve crop stress resistance and yield. This review focuses on the distribution, biosynthesis, and role of PAs in plant growth and development, abiotic stress tolerance, and the involvement of a possible novel interlinked signaling cascade between them. Further, we focused on our current understanding and knowledge gaps of how PAs interact with other signaling molecules like hormones and nitric oxide (NO) to regulate plant growth and stress tolerance in a coordinated manner. We also provide an overview of PA signaling in plants, focusing on calcium (Ca 2+ ) and reactive oxygen species (ROS) under abiotic stress, and some key insights into omics and nanotechnology approach for future research.

Plants face multifactorial environmental stressors mainly due to global warming and climate change which affect their growth, metabolism, and productivity. Among them, is drought stress which alters intracellular water relations, photosynthesis, ion homeostasis and elevates reactive oxygen species which eventually reduce their growth and yields. In addition, drought alters soil physicochemical properties and beneficial microbiota which are critical for plant survival. Recent reports have shown that climate change is increasing the occurrence and intensity of drought in many regions of the world, which has become a primary concern in crop productivity, ecophysiology and food security. To develop ideas and strategies for protecting plants against the harmful effects of drought stress and meeting the future food demand under climatic calamities an in-depth understanding of molecular regulatory pathways governing plant stress responses is imperative. In parallel, more research is needed to understand how drought changes the features of soil, particularly microbiomes, as microorganisms can withstand drought stress faster than plants, which could assist them to recover. In this review we first discuss the effect of drought stress on plants, soil physicochemical properties and microbiomes. How drought stress affects plant microbe interactions and other microbe-driven beneficial traits was also highlighted. Next, we focused on how plants sense drought and undergo biochemical reprogramming from root to shoot to regulate diverse adaptive traits. For instance, the role of calcium (Ca 2+ ), reactive oxygen species (ROS) and abscisic acid (ABA) in modulating different cellular responses like stomata functioning, osmotic adjustment, and other adaptive traits. We also provide an update on the role of different hormones in drought signaling and their crosstalk which allows plants to fine tune their responses during drought stress. Further, we discussed how recurrent drought exposure leads to the development of short-term memory in plants that allows them to survive future drought stresses. Lastly, we discussed the application of omics and biotechnological-based mitigating approaches to combat drought stress in sustainable agriculture. This review offers a deeper understanding of multiple factors that are related to drought stress in plants which can be useful for drought improvement programs.

Plant growth-promoting rhizobacteria (PGPR) are considered as bio-ameliorators that confer better salt resistance to host plants while improving soil biological activity. Despite their importance, data about the likely synergisms between PGPR and halophytes in their native environments are scarce. The objective of this study was to assess the effect of PGPR ( Glutamicibacter sp. and Pseudomonas sp.) inoculation on biomass, nutrient uptake, and antioxidant enzymes of Suaeda fruticosa , an obligate halophyte native in salt marshes and arid areas in Tunisia. Besides, the activity of rhizospheric soil enzyme activities upon plant inoculation was determined. Plants were grown in pots filled with soil and irrigated with 600 mM NaCl for 1 month. Inoculation (either with Pseudomonas sp. or Glutamicibacter sp.) resulted in significantly higher shoot dry weight and less accumulation of Na + and Cl – in shoots of salt-treated plants. Glutamicibacter sp. inoculation significantly reduced malondialdehyde (MDA) concentration, while increasing the activity of antioxidant enzymes (superoxide dismutase; catalase; ascorbate peroxidase; and glutathione reductase) by up to 100%. This provides strong arguments in favor of a boosting effect of this strain on S. fruticosa challenged with high salinity. Pseudomonas sp. inoculation increased shoot K + and Ca 2+ content and lowered shoot MDA concentration. Regarding the soil biological activity, Pseudomonas sp. significantly enhanced the activities of three rhizospheric soil enzymes (urease, ß-glucosidase, and dehydrogenase) as compared to their respective non-inoculated saline treatment. Hence, Pseudomonas sp. could have a great potential to be used as bio-inoculants in order to improve plant growth and soil nutrient uptake under salt stress. Indole-3-acetic acid concentration in the soil increased in both bacterial treatments under saline conditions, especially with Glutamicibacter sp. (up to +214%). As a whole, Glutamicibacter sp. and Pseudomonas sp. strains are promising candidates as part of biological solutions aiming at the phytoremediation and reclamation of saline-degraded areas.

Beneficial microbes or their products have been key drivers for improving adaptive and growth features in plants under biotic and abiotic stress conditions. However, the majority of these studies so far have been utilized against individual stressors. In comparison to individual stressors, the combination of many environmental stresses that plants experience has a greater detrimental effect on them and poses a threat to their existence. Therefore, there is a need to explore the beneficial microbiota against combined stressors or multiple stressors, as this will offer new possibilities for improving plant growth and multiple adaptive traits. However, recognition of the multifaceted core beneficial microbiota from plant microbiome under stress combinations will require a thorough understanding of the functional and mechanistic facets of plant microbiome interactions under different environmental conditions in addition to agronomic management practices. Also, the development of tailored beneficial multiple stress tolerant microbiota in sustainable agriculture necessitates new model systems and prioritizes agricultural microbiome research. In this review, we provided an update on the effect of combined stressors on plants and their microbiome structure. Next, we discussed the role of beneficial microbes in plant growth promotion and stress adaptation. We also discussed how plant-beneficial microbes can be utilized for mitigating multiple stresses in plants. Finally, we have highlighted some key points that warrant future investigation for exploring plant microbiome interactions under multiple stressors.

We acknowledge the support of the 2021 SGR 00688 grant from AGAUR, Generalitat de Catalunya, Spain. SCK is supported by \\u201CAyuda RYC2019-027818-I financiada por MICIU/AEI/10.13039/501100011033 y por El FSE invierte en tu futuro\\u201D. The field trial was funded by the International Center for Biosaline Agriculture (ICBA) as part of its internally supported research projects.

Plants are very often confronted by different heavy metal (HM) stressors that adversely impair their growth and productivity. Among HMs, chromium (Cr) is one of the most prevalent toxic trace metals found in agricultural soils because of anthropogenic activities, lack of efficient treatment, and unregulated disposal. It has a huge detrimental impact on the physiological, biochemical, and molecular traits of crops, in addition to being carcinogenic to humans. In soil, Cr exists in different forms, including Cr (III) “trivalent” and Cr (VI) “hexavalent”, but the most pervasive and severely hazardous form to the biota is Cr (VI). Despite extensive research on the effects of Cr stress, the exact molecular mechanisms of Cr sensing, uptake, translocation, phytotoxicity, transcript processing, translation, post-translational protein modifications, as well as plant defensive responses are still largely unknown. Even though plants lack a Cr transporter system, it is efficiently accumulated and transported by other essential ion transporters, hence posing a serious challenge to the development of Cr-tolerant cultivars. In this review, we discuss Cr toxicity in plants, signaling perception, and transduction. Further, we highlight various mitigation processes for Cr toxicity in plants, such as microbial, chemical, and nano-based priming. We also discuss the biotechnological advancements in mitigating Cr toxicity in plants using plant and microbiome engineering approaches. Additionally, we also highlight the role of molecular breeding in mitigating Cr toxicity in sustainable agriculture. Finally, some conclusions are drawn along with potential directions for future research in order to better comprehend Cr signaling pathways and its mitigation in sustainable agriculture.

Wheat (Triticum aestivum L.) is a strategic food crop for arid, hot regions such as the Arabian Peninsula, the Middle East, and North Africa. In these areas, production is limited by extreme environmental and agronomic conditions, leading to heavy dependence on imported wheat. Irrigation is often essential for successful cultivation, but available water sources are frequently saline. This study evaluated the comparative effects of irrigation salinity and genotype on agronomic performance, physiological responses, and grain quality. Nine Syrian wheat genotypes and one French bread-making cultivar, Florence Aurora, were grown in sandy soil under three irrigation salinity levels (2.6, 10, and 15 dS m−1) across two seasons at the International Center for Biosaline Agriculture (Dubai, UAE). Salinity strongly negatively impacted yield, which decreased by 61% from the control to 15 dS m−1, along with key yield components such as thousand grain weight and total biomass. Physiological traits, including carbon isotope composition (δ13C) and Na concentrations in roots, shoots and grains, increased significantly with salinity, while chlorophyll content showed a modest decline. Effects on grain quality were relatively minor: total nitrogen concentration and most mineral levels increased slightly, mainly due to a passive concentration effect associated with reduced TGW. Genotypes varied significantly in yield, biomass, TGW, physiological traits, and grain quality. The highest-yielding genotypes under control conditions (ACSAD 981 and ACSAD 1147) also performed best under saline conditions, and no trade-off was observed between yield and grain quality parameters (TGW, nitrogen, zinc, and iron concentrations). Separate analyses conducted for control and saline treatments identified different drivers of genotypic variability. Under control conditions, chlorophyll content, closely linked with δ13C, was the best predictor of genotypic differences and was positively correlated with yield across genotypes. Under salinity stress, grain magnesium (Mg) concentration was the strongest predictor, followed by grain δ13C, with both traits positively correlated with yield. These findings highlight key physiological traits linked to salinity tolerance and offer insights into the mechanisms underlying genotypic variability under both optimal and saline irrigation conditions.

IntroductionThe date palm ( Phoenix dactylifera L.) is a major component of the agro-food systems of the arid regions. Since it is an indigenous tree, it is an integral part of the local cultural heritage and social and economic life. Date palm cultivation in the region is challenging due to various factors such as water scarcity and soil and water salinity.MethodsThis research study was conducted to evaluate the quality of commonly sold date palm varieties in the UAE market and grown using saline water at the ICBA research station in Dubai. The study involved measuring physical parameters like fruit weight, size, dimensions, color, volume, Brix, protein, sucrose, glucose, fructose, sugars, phenols, sodium, and potassium, as well as analyzing how consumers perceive the fruit’s quality attributes produced under varying salinity levels. The study evaluated Tamar dates’ texture, flavor, aroma, taste, color, and appearance using a five-point scale from very poor to excellent.Results and discussionThe study found that fruit quality is affected by salinity, and there is a significant interaction between variety and salinity treatments. Salinity affects date palm traits, but low to moderate levels do not affect fruit quality. Khalas, Sukkari, and Ajwa-Tul-Madinah are the least affected varieties. High salinity negatively impacts some varieties, leading to decreased fruit quality. However, it is also worth noting that salinity stress can increase the sugar concentration in fruit for specific varieties, as demonstrated in this study on fruit sugar content under such conditions. Among the tested dates, Sukkari from the market, Ajwa-Tul-Madinah irrigated with 5 and 10 dS m−1 have the highest sugar content and many other desirable characteristics. Hierarchical k -means clustering reveals that each genotype performs better under a specific level of salinity, allowing for targeted selection of genotypes for salinity mitigation. Sugar content is crucial in assessing date fruits irrigated with saline water. It should be included in the evaluation criteria to promote the use of saline water for date palm irrigation and save freshwater resources. The study provides valuable insights into different date palm varieties’ behavior under varying salinity levels, enabling farmers to optimize production and establish new evaluation criteria.

Global food production intensification presents a major hurdle to ensuring food security amidst a growing world population. Widespread use of chemical fertilizers in recent decades has risked soil fertility, compounded by the challenges posed by climate change, particularly in arid regions. To address these issues, adopting plant growth-promoting (PGP) bacteria stands out as a promising solution, offering multifaceted benefits to arid agroecosystems. We isolated a bacterial strain, SW7, from mangrove sediment, characterised the entire genome followed by phylogenetic analyses, and evaluated its in-vitro PGP activity. Subsequently, we examined its impact on tomato seed germination and plant growth. The strain SW7 exhibited growth on 11% NaCl, survival at 50°C, and possessed multiple PGP traits such as significant increase in seed germination rate (60.60 ± 38.85%), phosphate (83.3 g L −1 ) and potassium (39.6 g L −1 ) solubilization and produced indole acetic acid (3.60 ppm). Additionally, strain SW7 tested positive for ammonia, catalase, and oxidase enzyme production. The strain SW7 genome consists of 5.1 MB with 35.18% G+C content. Through genome-based phylogenetic and orthoANI analyses, the strain was identified as a novel Bacillus species, designated herein as Bacillus sp. SW7. In an eight-week shade-house experiment, inoculation of strain SW7 improved, leaf number, leaf density, leaf area index and mass water of tomatoes. Additional parameters, like chlorophyll a, chlorophyll b and carotenoids were not affected in SW7-inoculated tomatoes. In conclusion, Bacillus sp. SW7 exhibits multiple PGP traits and an adaptive capacity to high temperature and salinity, positioning it as a potential candidate for elevating the productivity of arid agroecosystems.

Microalgae have gained popularity over the century due to their numerous intrinsic properties superior to higher plants, making them a potential target and feedstock for the development of biotechnological products in various fields. The storage of carbohydrates within microalgae cells positions them as a promising reservoir for biofuel production and a range of other valuable bioproducts, encompassing biological compounds, nutritional supplements, and more. Key determinants influencing microalgae carbohydrate levels comprise nutrient availability, light intensity, temperature, and CO2 concentrations. In this context, the CO2 concentration plays a key role, as it is one of the main factors influencing the photosynthetic processes. This study aimed to explore the impact of different CO2 concentrations on the carbohydrate profile of biomass sourced from Chlorella vulgaris sp. BB-2 and Scenedesmus quadicauda B-1. The findings revealed that a CO2 concentration of 2% v/v notably enhanced carbohydrate accumulation, reaching 75.5% for Chlorella vulgaris sp. BB-2 and 72.0% for Scenedesmus quadicauda B-1.