Aquaporin genes GintAQPF1 and GintAQPF2 from Glomus intraradices contribute to plant drought tolerance

Arbuscular mycorrhizal fungal contribution towards plant resilience to drought conditions

Climate changes cause altering rainfall patterns resulting in an increase in drought occurrences globally. These events are disrupting plants and agricultural productivity. To evade droughts, plants try to adapt and modify in the best capacities possible. The plants have adapted by structurally modifying roots, stems, and leaves, as well as modifying functions. Lately, the association of microbial communities with plants has also been proven to be an important factor in aiding resilience. The fungal representatives of the microbial community also help safeguard the plants against drought. We discuss how these fungi associate with plants and contribute to evading drought stress. We specifically focus on Arbuscular mycorrhizal fungi (AMF) mediated mechanisms involving antioxidant defenses, phytohormone mediations, osmotic adjustments, proline expressions, fungal water absorption and transport, morphological modifications, and photosynthesis. We believe understanding the mechanisms would help us to optimize the use of fungi in agricultural practices. That way we could better prepare the plants for the anticipated future drought events.

Silicon and soil microorganisms improve rhizospheric soil health with bacterial community, plant growth, performance and yield

The interaction of silicon and soil microorganisms stimulates crop enhancement to ensure sustainable agriculture. Silicon may potentially increase nutrient availability in rhizosphere with improved plants' growth, development as it does not produce phytotoxicity. The rhizospheric microbiome accommodates a variety of microbial species that live in a small area of soil directly associated with the hidden half plants' system. Plant growth-promoting rhizobacteria (PGPR) play a major role in plant development in response to adverse climatic conditions. PGPRs may enhance the growth, quality, productivity in variety of crops, and mitigate abiotic stresses by reprogramming stress-induced physiological variations in plants via different mechanisms, such as synthesis of indole-3-acetic acid, 1-aminocyclopropane-1-carboxylate deaminase, exopolysaccharides, volatile organic compounds, atmospheric nitrogen fixation, and phosphate solubilization. Our article eye upon interactions of silicon and plant microbes which seems to be an opportunity for sustainable agriculture for series of crops and cropping systems in years to come, essential to safeguard the food security for masses.

The Perspective of Arbuscular Mycorrhizal Symbiosis in Rice Domestication and Breeding

In nature, symbiosis with arbuscular mycorrhizal (AM) fungi contributes to sustainable acquisition of phosphorus and other elements in over 80% of plant species; improving interactions with AM symbionts may mitigate some of the environmental problems associated with fertilizer application in grain crops such as rice. Recent developments of high-throughput genome sequencing projects of thousands of rice cultivars and the discovery of the molecular mechanisms underlying AM symbiosis suggest that interactions with AM fungi might have been an overlooked critical trait in rice domestication and breeding. In this review, we discuss genetic variation in the ability of rice to form AM symbioses and how this might have affected rice domestication. Finally, we discuss potential applications of AM symbiosis in rice breeding for more sustainable agriculture.

Sustainable Approaches to Boost Yield and Chemical Constituents of Aromatic and Medicinal Plants by Application of Biostimulants

INTRODUCTION

Biostimulants consist of natural ingredients, metabolites of fermentation, micro-organisms, algae or plant extracts, bacteria, mushrooms, humus substances, amino acids, biomolecules, etc. Methods: In this study, all relevant English-language articles were collected. The literature was reviewed using the keywords of biostimulant, medicinal plant, aromatic plant, natural products, and pharmaceutical benefits from Google Scholar, Scopus, and PubMed databases.

RESULTS

The significant and promoting impact of biostimulants has been reported for different medicinal and aromatic plants, such as salicylic acid for ajuga, artichoke, ajwain, basil, common rue, common sage, common thyme, coneflower, coriander, dendrobium, desert Indian wheat, dragonhead, fennel, fenugreek, feverfew, ginger, groundnut, guava, henna, Iranian soda, lavender, lemon balm, lemongrass, Malabar spinach; seaweed extract on almond, bird, s eye chili; amino acids on artemisia, broccoli, chamomile, beneficial bacteria on ashwagandha; humic acid on black cumin, cannabis, chicory, garlic, gerbera, Hungarian vetch, Moldavian dragonhead, niger plant; chitosan on dragon fruit, marigold, milk thistle, etc. The suggested mechanisms include the stimulatory impacts on the activity of enzymes involved in different biosynthetic processes, the hormone-like activity of biostimulant compounds and the improvement of nutrient uptake of plants.

CONCLUSION

The current manuscript gives many examples of the potential of biostimulants for medicinal and aromatic plant production. However, further studies are needed to better understand the effectiveness of different biostimulants and foliar applications in sustainable agriculture.

Advancement in the molecular perspective of plant-endophytic interaction to mitigate drought stress in plants

Change in global climate has started to show its effect in the form of extremes of temperatures and water scarcity which is bound to impact adversely the global food security in near future. In the current review we discuss the impact of drought on plants and highlight the ability of endophytes, microbes that inhabit the plants asymptomatically, to confer stress tolerance to their host. For this we first describe the symbiotic association between plant and the endophytes and then focus on the molecular and physiological strategies/mechanisms adopted by these endophytes to confer stress tolerance. These include root alteration, osmotic adjustment, ROS scavenging, detoxification, production of phytohormones, and promoting plant growth under adverse conditions. The review further elaborates on how omics-based techniques have advanced our understanding of molecular basis of endophyte mediated drought tolerance of host plant. Detailed analysis of whole genome sequences of endophytes followed by comparative genomics facilitates in identification of genes involved in endophyte-host interaction while functional genomics further unveils the microbial targets that can be exploited for enhancing the stress tolerance of the host. Thus, an amalgamation of endophytes with other sustainable agricultural practices seems to be an appeasing approach to produce climate-resilient crops.

The Potential Role of Microbial Biostimulants in the Amelioration of Climate Change-Associated Abiotic Stresses on Crops

Crop plants are more often exposed to abiotic stresses in the current age of fast-evolving climate change. This includes exposure to extreme and unpredictable changes in climatic conditions, phytosanitary hazards, and cultivation conditions, which results in drastic losses in worldwide agricultural productions. Plants coexist with microbial symbionts, some of which play key roles in the ecosystem and plant processes. The application of microbial biostimulants, which take advantage of symbiotic relationships, is a long-term strategy for improving plant productivity and performance, even in the face of climate change-associated stresses. Beneficial filamentous fungi, yeasts, and bacteria are examples of microbial biostimulants, which can boost the growth, yield, nutrition and stress tolerance in plants. This paper highlights recent information about the role of microbial biostimulants and their potential application in mitigating the abiotic stresses occurring on crop plants due to climate change. A critical evaluation for their efficient use under diverse climatic conditions is also made. Currently, accessible products generally improve cultural conditions, but their action mechanisms are mostly unknown, and their benefits are frequently inconsistent. Thus, further studies that could lead to the more precisely targeted products are discussed.

Plant Growth Promoting Rhizobacteria, Arbuscular Mycorrhizal Fungi and Their Synergistic Interactions to Counteract the Negative Effects of Saline Soil on Agriculture: Key Macromolecules and Mechanisms

Soil saltiness is a noteworthy issue as it results in loss of profitability and development of agrarian harvests and decline in soil health. Microorganisms associated with plants contribute to their growth promotion and salinity tolerance by employing a multitude of macromolecules and pathways. Plant growth promoting rhizobacteria (PGPR) have an immediate impact on improving profitability based on higher crop yield. Some PGPR produce 1-aminocyclopropane-1-carboxylic (ACC) deaminase (EC 4.1.99.4), which controls ethylene production by diverting ACC into α-ketobutyrate and ammonia. ACC deaminase enhances germination rate and growth parameters of root and shoot in different harvests with and without salt stress. Arbuscular mycorrhizal fungi (AMF) show a symbiotic relationship with plants, which helps in efficient uptake of mineral nutrients and water by the plants and also provide protection to the plants against pathogens and various abiotic stresses. The dual inoculation of PGPR and AMF enhances nutrient uptake and productivity of several crops compared to a single inoculation in both normal and stressed environments. Positively interacting PGPR + AMF combination is an efficient and cost-effective recipe for improving plant tolerance against salinity stress, which can be an extremely useful approach for sustainable agriculture.

Arbuscular Mycorrhiza-Mediated Regulation of Polyamines and Aquaporins During Abiotic Stress: Deep Insights on the Recondite Players

Environmental stresses of (a)biotic origin induce the production of multitudinous compounds (metabolites and proteins) as protective defense mechanisms in plants. On account of the regulation of some of these compounds, arbuscular mycorrhizal fungi (AMF) reinforce the inherent tolerance of plants toward the stress of different origins and kind. This article reviews two specific fundamental mechanisms that are categorically associated with mycorrhiza in alleviating major abiotic stresses, salt, drought, and heavy metal (HM) toxicity. It puts emphasis on aquaporins (AQPs), the conduits of water and stress signals; and polyamines (PAs), the primordial stress molecules, which are regulated by AMF to assure water, nutrient, ion, and redox homeostasis. Under stressful conditions, AMF-mediated host AQP responses register distinct patterns: an upregulation to encourage water and nutrient uptake; a downregulation to restrict water loss and HM uptake; or no alterations. The patterns thereof are apparently an integrative outcome of the duration, intensity, and type of stress, AMF species, the interaction of fungal AQPs with that of plants, and the host type. However, the cellular and molecular bases of mycorrhizal influence on host AQPs are largely unexplored. The roles of PAs in augmenting the antioxidant defense system and improving the tolerance against oxidative stress are well-evident. However, the precise mechanism by which mycorrhiza accords stress tolerance by influencing the PA metabolism per se is abstruse and broadly variable under different stresses and plant species. This review comprehensively analyzes the current state-of-art of the involvement of AMF in "PA and AQP modulation" under abiotic stress and identifies the lesser-explored landscapes, gaps in understanding, and the accompanying challenges. Finally, this review outlines the prospects of AMF in realizing sustainable agriculture and provides insights into potential thrust areas of research on AMF and abiotic stress.

Fungal X-Intrinsic Protein Aquaporin from Trichoderma atroviride: Structural and Functional Considerations

The major intrinsic protein (MIP) superfamily is a key part of the fungal transmembrane transport network. It facilitates the transport of water and low molecular weight solutes across biomembranes. The fungal uncharacterized X-Intrinsic Protein (XIP) subfamily includes the full protein diversity of MIP. Their biological functions still remain fully hypothetical. The aim of this study is still to deepen the diversity and the structure of the XIP subfamily in light of the MIP counterparts—the aquaporins (AQPs) and aquaglyceroporins (AQGPs)—and to describe for the first time their function in the development, biomass accumulation, and mycoparasitic aptitudes of the fungal bioagent Trichoderma atroviride. The fungus-XIP clade, with one member (TriatXIP), is one of the three clades of MIPs that make up the diversity of T. atroviride MIPs, along with the AQPs (three members) and the AQGPs (three members). TriatXIP resembles those of strict aquaporins, predicting water diffusion and possibly other small polar solutes due to particularly wider ar/R constriction with a Lysine substitution at the LE2 position. The XIP loss of function in ∆TriatXIP mutants slightly delays biomass accumulation but does not impact mycoparasitic activities. ∆TriatMIP forms colonies similar to wild type; however, the hyphae are slightly thinner and colonies produce rare chlamydospores in PDA and specific media, most of which are relatively small and exhibit abnormal morphologies. To better understand the molecular causes of these deviant phenotypes, a wide-metabolic survey of the ∆TriatXIPs demonstrates that the delayed growth kinetic, correlated to a decrease in respiration rate, is caused by perturbations in the pentose phosphate pathway. Furthermore, the null expression of the XIP gene strongly impacts the expression of four expressed MIP-encoding genes of T. atroviride, a plausible compensating effect which safeguards the physiological integrity and life cycle of the fungus. This paper offers an overview of the fungal XIP family in the biocontrol agent T. atroviride which will be useful for further functional analysis of this particular MIP subfamily in vegetative growth and the environmental stress response in fungi. Ultimately, these findings have implications for the ecophysiology of Trichoderma spp. in natural, agronomic, and industrial systems.

Facing Climate Change: Application of Microbial Biostimulants to Mitigate Stress in Horticultural Crops

In the current scenario of rapidly evolving climate change, crop plants are more frequently subjected to stresses of both abiotic and biotic origin, including exposure to unpredictable and extreme climatic events, changes in plant physiology, growing season and phytosanitary hazard, and increased losses up to 30% and 50% in global agricultural productions. Plants coevolved with microbial symbionts, which are involved in major functions both at the ecosystem and plant level. The use of microbial biostimulants, by exploiting this symbiotic interaction, represents a sustainable strategy to increase plant performances and productivity, even under stresses due to climate changes. Microbial biostimulants include beneficial fungi, yeasts and eubacteria sharing the ability to improve plant nutrition, growth, productivity and stress tolerance. This work reports the current knowledge on microbial biostimulants and provides a critical review on their possible use to mitigate the biotic and abiotic stresses caused by climate changes. Currently, available products often provide a general amelioration of cultural conditions, but their action mechanisms are largely undetermined and their effects often unreliable. Future research may lead to more specifically targeted products, based on the characterization of plant-microbe and microbial community interactions.

Reducing Water Availability Impacts the Development of the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis MUCL 41833 and Its Ability to Take Up and Transport Phosphorus Under in Vitro Conditions

Climate change scenarios predict a higher variability in rainfall and an increased risk of water deficits during summers for the coming decades. For this reason, arbuscular mycorrhizal fungi (AMF) and their mitigating effects on drought stress in plants are increasingly considered in crop management. However, the impact of a decrease in water availability on the development of AMF and their ability to take up and transport inorganic phosphorus (Pi) to their hosts remain poorly explored. Here, Medicago truncatula plantlets were grown in association with Rhizophagus irregularis MUCL 41833 in bi-compartmented Petri plates. The system consisted in associating the plant and AMF in a root compartment (RC), allowing only the hyphae to extend in a root-free hyphal compartment (HC). Water availability in the HC was then lowered by increasing the concentration of polyethylene glycol-8000 (PEG-8000) from 0 to 10, 25, and 50 g L-1 (corresponding to a slight decrease in water potential of -0.024, -0.025, -0.030, and -0.056 Mpa, respectively). Hyphal growth, spore production and germination were severely impaired at the lowest water availability. The dynamics of Pi uptake by the AMF was also impacted, although total Pi uptake evaluated after 24 h stayed unchanged. The percentage of metabolically active extraradical hyphae remained above 70%. Finally, at the lowest water availability, a higher P concentration was observed in the shoots of M. truncatula. At reduced water availability, the extraradical mycelium (ERM) development was impacted, potentially limiting its capacity to explore a higher volume of soil. Pi uptake was slowed down but not prevented. The sensitivity of R. irregularis MUCL 41833 to a, even small, decrease in water availability contrasted with several studies reporting tolerance of AMF to drought. This suggests a species or strain-dependent effect and support the necessity to compare the impact of water availability on morpho-anatomy, nutrient uptake and transport capacities of other, potentially more drought-tolerant (e.g., isolated from dry environments) AMF.

MIP diversity from Trichoderma: Structural considerations and transcriptional modulation during mycoparasitic association with Fusarium solani olive trees

Major intrinsic proteins (MIP) are characterized by a transmembrane pore-type architecture that facilitates transport across biomembranes of water and a variety of low molecular weight solutes. They are found in all parts of life, with remarkable protein diversity. Very little is known about MIP from fungi. And yet, it can legitimately be stated that MIP are pivotal molecular components in the privileged relationships fungi enjoy with plants or soil fauna in various environments. To date, MIP have never been studied in a mycoparasitism situation. In this study, the diversity, expression and functional prediction of MIP from the genus Trichoderma were investigated. Trichoderma spp. genomes have at least seven aquaporin genes. Based on a phylogenetic analysis of the translated sequences, members were assigned to the AQP, AQGP and XIP subfamilies. In in vitro and in planta assays with T. harzianum strain Ths97, expression analyses showed that four genes were constitutively expressed. In a mycoparasitic context with Fusarium solani, the causative agent of fusarium dieback on olive tree roots, these genes were up-regulated. This response is of particular interest in analyzing the MIP promoter cis-regulatory motifs, most of which are involved in various carbon and nitrogen metabolisms. Structural analyses provide new insights into the possible role of structural checkpoints by which these members transport water, H2O2, glycerol and, more generally, linear polyols across the membranes. Taken together, these results provide the first evidence that MIP may play a key role in Trichoderma mycoparasitism lifestyle.

Arbuscular mycorrhiza effects on plant performance under osmotic stress

At present, drought and soil salinity are among the most severe environmental stresses that affect the growth of plants through marked reduction of water uptake which lowers water potential, leading to osmotic stress. In general, osmotic stress causes a series of morphological, physiological, biochemical, and molecular changes that affect plant performance. Several studies have found that diverse types of soil microorganisms improve plant growth, especially when plants are under stressful conditions. Most important are the arbuscular mycorrhizal fungi (AMF) which form arbuscular mycorrhizas (AM) with approximately 80% of plant species and are present in almost all terrestrial ecosystems. Beyond the well-known role of AM in improving plant nutrient uptake, the contributions of AM to plants coping with osmotic stress merit analysis. With this review, we describe the principal direct and indirect mechanisms by which AM modify plant responses to osmotic stress, highlighting the role of AM in photosynthetic activity, water use efficiency, osmoprotectant production, antioxidant activities, and gene expression. We also discuss the potential for using AMF to improve plant performance under osmotic stress conditions and the lines of research needed to optimize AM use in plant production.

An in vivo whole-plant experimental system for the analysis of gene expression in extraradical mycorrhizal mycelium

Arbuscular mycorrhizal fungi (AMF) establish beneficial mutualistic symbioses with land plants, receiving carbon in exchange for mineral nutrients absorbed by the extraradical mycelium (ERM). With the aim of obtaining in vivo produced ERM for gene expression analyses, a whole-plant bi-dimensional experimental system was devised and tested with three host plants and three fungal symbionts. In such a system, Funneliformis mosseae in symbiosis with Cichorium intybus var. foliosum, Lactuca sativa, and Medicago sativa produced ERM whose lengths ranged from 9.8 ± 0.8 to 20.8 ± 1.2 m per plant. Since ERM produced in symbiosis with C. intybus showed the highest values for the different structural parameters assessed, this host was used to test the whole-plant system with F. mosseae, Rhizoglomus irregulare, and Funneliformis coronatus. The whole-plant system yielded 1-7 mg of ERM fresh biomass per plant per harvest, and continued producing new ERM for 6 months. Variable amounts of high-quality and intact total RNA, ranging from 15 to 65 μg RNA/mg ERM fresh weight, were extracted from the ERM of the three AMF isolates. Ammonium transporter gene expression was successfully determined in the cDNAs obtained from ERM of the three fungal symbionts by RT-qPCR using gene-specific primers designed on available (R. irregulare) and new (F. mosseae and F. coronatus) ammonium transporter gene sequences. The whole-plant experimental system represents a useful research tool for large production and easy collection of ERM for morphological, physiological, and biochemical analyses, suitable for a wide variety of AMF species, for a virtually limitless range of host plants and for studies involving diverse symbiotic interactions.

Take a Trip Through the Plant and Fungal Transportome of Mycorrhiza

Soil nutrient acquisition and exchanges through symbiotic plant-fungus interactions in the rhizosphere are key features for the current agricultural and environmental challenges. Improved crop yield and plant mineral nutrition through a fungal symbiont has been widely described. In return, the host plant supplies carbon substrates to its fungal partner. We review here recent progress on molecular players of membrane transport involved in nutritional exchanges between mycorrhizal plants and fungi. We cover the transportome, from the transport proteins involved in sugar fluxes from plants towards fungi, to the uptake from the soil and exchange of nitrogen, phosphate, potassium, sulfate, and water. Together, these advances in the comprehension of the mycorrhizal transportome will help in developing the future engineering of new agro-ecological systems.

Insights on the Impact of Arbuscular Mycorrhizal Symbiosis on Tomato Tolerance to Water Stress

Arbuscular mycorrhizal (AM) fungi, which form symbioses with the roots of the most important crop species, are usually considered biofertilizers, whose exploitation could represent a promising avenue for the development in the future of a more sustainable next-generation agriculture. The best understood function in symbiosis is an improvement in plant mineral nutrient acquisition, as exchange for carbon compounds derived from the photosynthetic process: this can enhance host growth and tolerance to environmental stresses, such as water stress (WS). However, physiological and molecular mechanisms occurring in arbuscular mycorrhiza-colonized plants and directly involved in the mitigation of WS effects need to be further investigated. The main goal of this work is to verify the potential impact of AM symbiosis on the plant response to WS To this aim, the effect of two AM fungi (Funneliformis mosseae and Rhizophagus intraradices) on tomato (Solanum lycopersicum) under the WS condition was studied. A combined approach, involving ecophysiological, morphometric, biochemical, and molecular analyses, has been used to highlight the mechanisms involved in plant response to WS during AM symbiosis. Gene expression analyses focused on a set of target genes putatively involved in the plant response to drought, and in parallel, we considered the expression changes induced by the imposed stress on a group of fungal genes playing a key role in the water-transport process. Taken together, the results show that AM symbiosis positively affects the tolerance to WS in tomato, with a different plant response depending on the AM fungi species involved.

Insights on the Impact of Arbuscular Mycorrhizal Symbiosis on Tomato Tolerance to Water Stress

Arbuscular mycorrhizal (AM) fungi, which form symbioses with the roots of the most important crop species, are usually considered biofertilizers, whose exploitation could represent a promising avenue for the development in the future of a more sustainable next-generation agriculture. The best understood function in symbiosis is an improvement in plant mineral nutrient acquisition, as exchange for carbon compounds derived from the photosynthetic process: this can enhance host growth and tolerance to environmental stresses, such as water stress (WS). However, physiological and molecular mechanisms occurring in arbuscular mycorrhiza-colonized plants and directly involved in the mitigation of WS effects need to be further investigated. The main goal of this work is to verify the potential impact of AM symbiosis on the plant response to WS To this aim, the effect of two AM fungi (Funneliformis mosseae and Rhizophagus intraradices) on tomato (Solanum lycopersicum) under the WS condition was studied. A combined approach, involving ecophysiological, morphometric, biochemical, and molecular analyses, has been used to highlight the mechanisms involved in plant response to WS during AM symbiosis. Gene expression analyses focused on a set of target genes putatively involved in the plant response to drought, and in parallel, we considered the expression changes induced by the imposed stress on a group of fungal genes playing a key role in the water-transport process. Taken together, the results show that AM symbiosis positively affects the tolerance to WS in tomato, with a different plant response depending on the AM fungi species involved.

Dose-dependent response of Trichoderma harzianum in improving drought tolerance in rice genotypes

This study demonstrates a dose-dependent response of Trichoderma harzianum Th-56 in improving drought tolerance in rice by modulating proline, SOD, lipid peroxidation product and DHN / AQU transcript level, and the growth attributes. In the present study, the effect of colonization of different doses of T. harzianum Th-56 strain in rice genotypes were evaluated under drought stress. The rice genotypes treated with increasing dose of T. harzianum strain Th-56 showed better drought tolerance as compared with untreated control plant. There was significant change in malondialdehyde, proline, higher superoxide dismutase level, plant height, total dry matter, relative chlorophyll content, leaf rolling, leaf tip burn, and the number of scorched/senesced leaves in T. harzianum Th-56 treated rice genotypes under drought stress. This was corroborated with altered expression of aquaporin and dehydrin genes in T. harzianum Th-56 treated rice genotypes. The present findings suggest that a dose of 30 g/L was the most effective in improving drought tolerance in rice, and its potential exploitation will contribute to the advancement of rice genotypes to sustain crop productivity under drought stress. Interaction studies of T. harzianum with three aromatic rice genotypes suggested that PSD-17 was highly benefitted from T. harzianum colonization under drought stress.

Aspergillus glaucus Aquaglyceroporin Gene glpF Confers High Osmosis Tolerance in Heterologous Organisms

Aquaglyceroporins (GlpFs) that transport glycerol along with water and other uncharged solutes are involved in osmoregulation in myriad species. Fungal species form a large group of eukaryotic organisms, and their GlpFs may be diverse, exhibiting various activities. However, few filamentous fungal GlpFs have been biologically investigated. Here, a glpF gene from the halophilic fungus Aspergillus glaucus (AgglpF) was verified to be a channel of water or glycerol in Xenopus laevis oocytes and was further functionally analyzed in three heterologous systems. In Saccharomyces cerevisiae, cells overexpressing AgglpF possessed significant tolerance of drought, salt, and certain metal ions. AgglpF was then characterized in the filamentous fungus of Neurospora crassa. Based on the N. crassa aquaporin gene (NcAQP) disruption mutant (the Δaqp mutant), a series of complementary strains carrying NcAQP and AgglpF and three asparagine-proline-alanine-gene (NPA)-deleted AgglpF fragments were created. As revealed by salt resistance analysis, the AgglpF complementary strain possessed the highest salt resistance among the tested strains. In addition, the intracellular glycerol content in the AgglpF complementary strain was markedly higher than that in the other strains. The AgGlpF-green fluorescent protein (GFP) fusion protein was subcellularly localized in the plasma membrane of onion epidermal cells, suggesting that AgglpF functions in plants. Indeed, when AgglpF was expressed in Arabidopsis thaliana, transgenic lines survived under conditions of high osmotic stress and under conditions of drought stress in particular. Overall, our results revealed that AgGlpF as a water/glycerol transporter is required for survival of both fungi and plants under conditions of high osmotic stress and may have value in applications in genetic engineering for generating high salt and drought resistance.

Membrane transporters and drought resistance - a complex issue

Land plants have evolved complex adaptation strategies to survive changes in water status in the environment. Understanding the molecular nature of such adaptive changes allows the development of rapid innovations to improve crop performance. Plant membrane transport systems play a significant role when adjusting to water scarcity. Here we put proteins participating in transmembrane allocations of various molecules in the context of stomatal, cuticular, and root responses, representing a part of the drought resistance strategy. Their role in the transport of signaling molecules, ions or osmolytes is summarized and the challenge of the forthcoming research, resulting from the recent discoveries, is highlighted.