Effect of IAA on in vitro growth and colonization of Nostoc in plant roots

Emerging nitrogen-fixing cyanobacteria for sustainable cotton cultivation

Amid growing environmental concerns and the imperative for sustainable agricultural practices, this study examines the potential of nitrogen-fixing cyanobacteria as biofertilizers, particularly in cotton cultivation. The reliance on synthetic nitrogen fertilizers (SNFs), prevalent in modern agriculture, poses significant environmental challenges, including greenhouse gas emissions and water system contamination. This research aims to shift this paradigm by exploring the capacity of cyanobacteria as a natural and sustainable alternative. Utilizing advanced metabarcoding methods to analyze the 16S rRNA gene, we conducted a comprehensive assessment of soil bacterial communities within cotton fields. This study focused on evaluating the diversity, structure, taxonomic composition, and potential functional characteristics of these communities. Emphasis was placed on the isolation of native N2-fixing cyanobacteria strains rom cotton soils, and their subsequent effects on cotton growth. Results from our study demonstrate significant plant growth-promoting (PGP) activities, measured as N2 fixation, production of Phytohormones, Fe solubilization and biofertilization potential of five isolated cyanobacterial strains, underscoring their efficacy in cotton. These findings suggest a viable pathway for replacing chemical-synthetic nitrogen fertilizers with natural, organic alternatives. The reintegration of these beneficial species into agricultural ecosystems can enhance crop growth while fostering a balanced microbial environment, thus contributing to the broader goals of global sustainable agriculture.

Using microalgae to reduce the use of conventional fertilizers in hydroponics and soil-based cultivation

The intensive use of agrochemicals has led to nutrient loss, greenhouse gas emissions, and resource depletion, thus the development of sustainable agricultural solutions is required. Microalgal biomass has the potential to provide nutrients such as nitrogen, phosphorus, and potassium, along with various plant growth promoters, to enhance crop productivity and impart disease resistance. This study provides a comprehensive assessment of the potential applications of microalgal extracts and biomass in the contexts of seed germination, hydroponic systems, and soil-based crop cultivation. The results revealed that the extracts from Chlorella sp. and Anabaena sp. have no significant impact on the germination of wheat seeds. High concentrations of Chlorella sp. and Anabaena sp. cell extracts in hydroponics enhanced the length of cucumber seedling stems by 81.7 % and 58.3 %, respectively. Additionally, the use of microalgal cell extracts hindered root elongation while stimulating the growth of lateral and fibrous roots. Furthermore, the study compared the performance of 5 different fertilizers: 1) inorganic fertilizer (IF), 2) organic fertilizer (OF), 3) microalgae-based biofertilizer (MF), 4) inorganic fertilizer + microalgae-based biofertilizer (IM), 5) organic fertilizer + microalgae-based biofertilizer (OM). The findings indicate that the plant growth and soil physicochemical properties in the groups supplied with different fertilizers are comparable and significantly higher than those in the control group. The levels of protein, chlorophyll A, and chlorophyll B in the MF group increased significantly by 40 %, 29.2 %, and 33.5 %, respectively, compared to the control group. However, it remained notably lower compared to groups supplied with inorganic and organic fertilizers (p < 0.05). Combining microalgae with organic fertilizer can simultaneously enhance the yield and quality of Chinese cabbage, representing a promising source of crop nutrition. In conclusion, this study suggests that it is promising to use microalgae to reduce the use of conventional fertilizers in hydroponics and soil-based cultivation.

Plant endophytes: unveiling hidden applications toward agro-environment sustainability

Endophytic microbes are plant-associated microorganisms that reside in the interior tissue of plants without causing damage to the host plant. Endophytic microbes can boost the availability of nutrient for plant by using a variety of mechanisms such as fixing nitrogen, solubilizing phosphorus, potassium, and zinc, and producing siderophores, ammonia, hydrogen cyanide, and phytohormones that help plant for growth and protection against various abiotic and biotic stresses. The microbial endophytes have attained the mechanism of producing various hydrolytic enzymes such as cellulase, pectinase, xylanase, amylase, gelatinase, and bioactive compounds for plant growth promotion and protection. The efficient plant growth promoting endophytic microbes could be used as an alternative of chemical fertilizers for agro-environmental sustainability. Endophytic microbes belong to different phyla including Euryarchaeota, Ascomycota, Basidiomycota, Mucoromycota, Firmicutes, Proteobacteria, and Actinobacteria. The most pre-dominant group of bacteria belongs to Proteobacteria including α-, β-, γ-, and δ-Proteobacteria. The least diversity of the endophytic microbes have been revealed from Bacteroidetes, Deinococcus-Thermus, and Acidobacteria. Among reported genera, Achromobacter, Burkholderia, Bacillus, Enterobacter, Herbaspirillum, Pseudomonas, Pantoea, Rhizobium, and Streptomyces were dominant in most host plants. The present review deals with plant endophytic diversity, mechanisms of plant growth promotion, protection, and their role for agro-environmental sustainability. In the future, application of endophytic microbes have potential role in enhancement of crop productivity and maintaining the soil health in sustainable manner.

Chloroplast Auxin Efflux Mediated by ABCB28 and ABCB29 Fine-Tunes Salt and Drought Stress Responses in Arabidopsis

Photosynthesis is among the first processes negatively affected by environmental cues and its performance directly determines plant cell fitness and ultimately crop yield. Primarily sites of photosynthesis, chloroplasts are unique sites also for the biosynthesis of precursors of the growth regulator auxin and for sensing environmental stress, but their role in intracellular auxin homeostasis, vital for plant growth and survival in changing environments, remains poorly understood. Here, we identified two ATP-binding cassette (ABC) subfamily B transporters, ABCB28 and ABCB29, which export auxin across the chloroplast envelope to the cytosol in a concerted action in vivo. Moreover, we provide evidence for an auxin biosynthesis pathway in Arabidopsis thaliana chloroplasts. The overexpression of ABCB28 and ABCB29 influenced stomatal regulation and resulted in significantly improved water use efficiency and survival rates during salt and drought stresses. Our results suggest that chloroplast auxin production and transport contribute to stomata regulation for conserving water upon salt stress. ABCB28 and ABCB29 integrate photosynthesis and auxin signals and as such hold great potential to improve the adaptation potential of crops to environmental cues.

Symbiosis between cyanobacteria and plants: from molecular studies to agronomic applications

Nitrogen-fixing cyanobacteria from the order Nostocales are able to establish symbiotic relationships with diverse plant species. They are promiscuous symbionts, as the same strain of cyanobacterium is able to form symbiotic biological nitrogen-fixing relationships with different plants species. This review will focus on the different types of cyanobacterial-plant associations, both endophytic and epiphytic, and provide insights from a structural viewpoint, as well as our current understanding of the mechanisms involved in the symbiotic crosstalk. In all these symbioses, the benefit for the plant is clear; it obtains from the cyanobacterium fixed nitrogen and other bioactive compounds, such as phytohormones, polysaccharides, siderophores, or vitamins, leading to enhanced plant growth and productivity. Additionally, there is increasing use of different cyanobacterial species as bio-inoculants for biological nitrogen fixation to improve soil fertility and crop production, thus providing an eco-friendly, alternative, and sustainable approach to reduce the over-reliance on synthetic chemical fertilizers.

Isolation and Characterisation of Culturable Thermophilic Cyanobacteria from Perak Hot Springs and their Plant Growth Promoting Properties Effects on Rice Seedlings (Oryza sativa L.)

Malaysia is home to a number of hot springs that are rich in microbial diversity including the photosynthetic cyanobacteria. Although this microbial community has been characterised based on metagenomics approach, the culturable thermophilic isolates have not been isolated and characterised extensively. Compared to the mesophiles, information on plant growth promoting (PGP) properties of these thermophiles remain largely untapped. As the amount of arable land for microbial bioprospecting is decreasing due to extensive human activities, the search for alternative source for microbial strains with PGP properties is important for the development of potential biofertilisers. This study sought to isolate and characterise culturable cyanobacteria strains from two local hot springs - Sungai Klah (SK) and Lubuk Timah (LT) located in Perak using morphological and molecular methods. The IAA production from the axenic cultures were measured. The PGP properties were also measured by priming the rice seeds with cyanobacterial water extracts. A total of six strains were isolated from both hot springs. Strains LTM and LTW from LT were identified as Leptolyngbya sp. whereas strains SEM, SEH, STH and STM were identified as Thermosynechococcus elongatus. All six strains produced IAA ranged from 670.10 pg/μL to 2010 pg/μL. The water extracts were found to increase the seed amylase activity of the rice seeds from 5th day of germination (DAG) to 10th DAG. In general, the IAA production and increased seed amylase activity might have contributed in enhancing the longest root length, shoot length and root-to-shoot (RS) ratio. To conclude, the thermophilic cyanobacteria from hot springs can be further exploited as a novel source of PGP microbes for the development of biofertilsers.

Isolation and characterization of a plant growth‑promoting rhizobacterium strain MD36 that promotes barley seedlings and growth under heavy metals stress

Plant growth, promoting, bacteria, (PGPB) can improve plant germination and growth in heavy metal-contaminated land and enhance heavy metal removal efficiency. In this study, we isolated PGPR bacterial strains which can withstand heavy metal pollution and tested their ability to improve barley germination under heavy metal stress. Out of 16 multi-resistant heavy metal isolates, strain MD36 was identified by 16S rRNA sequencing and shared close relation to different species of the genus Glutamicibacter. The new isolated strain showed other important PGPR activities, mainly IAA production and salt tolerance. The effect of adding the strain MD36 to barley grains under heavy metal stress enhanced their germination up to 100%, while the percentage of germination ranged between 0 and 20% for non-inoculated grains. In addition, in these conditions, MD36 can significantly enhance barley growth by reducing the heavy metal effect. This study strongly recommends the use of MD36 as seed coatings trials in the field to enhance growth and yield in soils contaminated with heavy metals, as well as in bioremediation of HM-contaminated salt-containing soils and water.

Microalgae as next generation plant growth additives: Functions, applications, challenges and circular bioeconomy based solutions

Sustainable agriculture practices involve the application of environment-friendly plant growth promoters and additives that do not negatively impact the health of the ecosystem. Stringent regulatory frameworks restricting the use of synthetic agrochemicals and the increase in demand for organically grown crops have paved the way for the development of novel bio-based plant growth promoters. In this context, microalgae biomass and derived agrochemicals offer novel sources of plant growth promotors that enhance crop productivity and impart disease resistance. These beneficial effects could be attributed to the presence of wide range of biomolecules such as soluble amino acid (AA), micronutrients, polysaccharides, phytohormones and other signaling molecules in microalgae biomass. In addition, their phototrophic nature, high photosynthetic efficiency, and wide environmental adaptability make them an attractive source of biostimulants, biofertilizers and biopesticides. The present review aims to describe the various plant growth promoting metabolites produced by microalgae and their effects on plant growth and productivity. Further, the effects elicited by microalgae biostimulants with respect to different modes of applications such as seed treatments, foliar spray and soil/root drenching is reviewed in detail. In addition, the ability of microalgae metabolites to impart tolerance against various abiotic and biotic stressors along with the mechanism of action is discussed in this paper. Although the use of microalgae based biofertilizers and biostimulants is gaining popularity, the high nutrient and water requirements and energy intensive downstream processes makes microalgae based technology commercially unsustainable. Addressing this challenge, we propose a circular economy model of microalgae mediated bioremediation coupled with biorefinery approaches of generating high value metabolites along with biofertilizer applications. We discuss and review new trends in enhancing the sustainability of microalgae biomass production by co-cultivation of algae with hydroponics and utilization of agriculture effluents.

Diversity, Lifestyle, Genomics, and Their Functional Role of Cochliobolus, Bipolaris, and Curvularia Species in Environmental Remediation and Plant Growth Promotion under Biotic and Abiotic Stressors

Cochliobolus, Bipolaris, and Curvularia genera contain various devastating plant pathogens that cause severe crop losses worldwide. The species belonging to these genera also perform a variety of diverse functions, including the remediation of environmental contaminations, beneficial phytohormone production, and maintaining their lifestyle as epiphytes, endophytes, and saprophytes. Recent research has revealed that despite their pathogenic nature, these fungi also play an intriguing role in agriculture. They act as phosphate solubilizers and produce phytohormones, such as indole acetic acid (IAA) and gibberellic acid (GAs), to accelerate the growth of various plants. Some species have also been reported to play a significant role in plant growth promotion during abiotic stresses, such as salinity stress, drought stress, heat stress, and heavy metal stress, as well as act as a biocontrol agent and a potential mycoherbicide. Similarly, these species have been reported in numerous industrial applications to produce different types of secondary metabolites and biotechnological products and possess a variety of biological properties, such as antibacterial, antileishmanial, cytotoxic, phytotoxic, and antioxidant activities. Additionally, some of the species have been utilized in the production of numerous valuable industrial enzymes and biotransformation, which has an impact on the growth of crops all over the world. However, the current literature is dispersed, and some of the key areas, such as taxonomy, phylogeny, genome sequencing, phytohormonal analysis, and diversity, are still being neglected in terms of the elucidation of its mechanisms, plant growth promotion, stress tolerance, and bioremediation. In this review, we highlighted the potential role, function, and diversity of Cochliobolus, Curvularia, and Bipolaris for improved utilization during environmental biotechnology.

Porostereum spadiceum-AGH786 Regulates the Growth and Metabolites Production in Triticum aestivum L. Under Salt Stress

The role of the most fungal endophytes in the host plant growth and production of metabolites under stress conditions is still unknown. Fungal endophytes occur in almost all plants to benefit the host plants exposed to biotic and abiotic stress. In the present work, we investigated salt (NaCl) stress alleviation capability of a fungal endophyte (Porostereum spadiceum-AGH786). The culture filtrate (CF: 1.5 mL.) of P. spadiceum-AGH786 contained IAA (158 µg/ml), SA (29.3 µg/ml), proline (114.6 µg/ml), phenols (167.4 µg/ml), lipids (71.4 µg/ml), sugar (133.2 µg/ml), flavonoids (105.04 µg/ml). Smaller amounts of organic acids, such as butyric acid (5.8 µg/ml), formic acid (2.34 µg/ml), succinic acid (2.02 µg/ml), and quinic acid (2.25 µg/ml) were also found in CF of P. spadiceum-AGH786. Similarly, the CF displayed antioxidant activity in 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. Moreover, wheat plants colonized by P. spadiceum-AGH786 showed significantly (P = 0.05) higher polyphenol oxidases activity (2.2 mg/g DW) under normal conditions as compared to the NaCl-treated plants. We also observed that P. spadiceum-AGH786 improved biomass (0.30 g) of wheat plants subjected to 140 mM NaCl stress. The results conclude that the wheat plant colonization by P. spadiceum-AGH786 greatly improved the plant growth under 70 mM and 140 mM NaCl stress. Thus, the biomass of the P. Spadiceum-AGH786 can be used in saline soil to help the host plants.

Plant-cyanobacteria interactions: Beneficial and harmful effects of cyanobacterial bioactive compounds on soil-plant systems and subsequent risk to animal and human health

Plant-cyanobacteria interactions occur in different ways and at many different levels, both beneficial and harmful. Plant-cyanobacteria interactions, as a beneficial symbiosis, have long been demonstrated in rice-growing areas (Poaceae) where the most efficient nitrogen-fixing cyanobacteria are present in paddies. Moreover, cyanobacteria may in turn produce and/or secrete numerous bioactive compounds that have plant growth-promoting abilities or that may make the plant more resistant to abiotic or biotic stress. In recent years, there has been a growing worldwide interest in the use of cyanobacterial biomass as biofertilizers to replace chemical fertilizers, in part to overcome increasing organic-farming demands. However, the potential presence of harmful cyanotoxins has delayed the use of such cyanobacterial biomass, which can be found in large quantities in freshwater ecosystems around the world. In this review, we describe the existing evidence for the positive benefit of plant-cyanobacteria interactions and discuss the use of cyanobacterial biomass as biofertilizers and its growing worldwide interest. Although mass cyanobacterial blooms and scums are a current and emerging threat to the degradation of ecosystems and to animal and human health, they may serve as a source of numerous bioactive compounds with multiple positive effects that could be of use as an alternative to chemical fertilizers in the context of sustainable development.

Pseudocitrobacter anthropi reduces heavy metal uptake and improves phytohormones and antioxidant system in Glycine max L

Heavy metal contamination due to anthropogenic activities is a great threat to modern humanity. A novel and natural technique of bioremediation using microbes for detoxification of heavy metals while improving plants' growth is the call of the day. In this study, exposing soybean plants to different concentrations (i.e., 10 and 50 ppm) of chromium and arsenic showed a severe reduction in agronomic attributes, higher reactive oxygen species production, and disruption in the antioxidant system. Contrarily, rhizobacterial isolate C18 inoculation not only rescued host growth, but also improved the production of nonenzymatic antioxidants (i.e., flavonoids, phenolic, and proline contents) and enzymatic antioxidants i.e., catalases, ascorbic acid oxidase, peroxidase activity, and 1,1-diphenyl-2-picrylhydrazyl, lower reactive oxygen species accumulation in leaves. Thereby, lowering secondary oxidative stress and subsequent damage. The strain was identified using 16 S rDNA sequencing and was identified as Pseudocitrobacter anthropi. Additionally, the strain can endure metals up to 1200 ppm and efficient in detoxifying the effect of chromium and arsenic by regulating phytohormones (IAA 59.02 µg/mL and GA 101.88 nM/mL) and solubilizing inorganic phosphates, making them excellent phytostimulant, biofertilizers, and heavy metal bio-remediating agent.

Algae as New Kids in the Beneficial Plant Microbiome

Previously, algae were recognized as small prokaryotic and eukaryotic organisms found only in aquatic habitats. However, according to a recent paradigm shift, algae are considered ubiquitous organisms, occurring in plant tissues as well as in soil. Accumulating evidence suggests that algae represent a member of the plant microbiome. New results indicate that plants respond to algae and activate related downstream signaling pathways. Application of algae has beneficial effects on plant health, such as plant growth promotion and disease control. Although accumulating evidence suggests that secreted compounds and cell wall components of algae induce physiological and structural changes in plants that protect against biotic and abiotic stresses, knowledge of the underlying mechanisms and algal determinants is limited. In this review, we discuss recent studies on this topic, and highlight the bioprotectant and biostimulant roles of algae as a new member of the plant beneficial microbiome for crop improvement.

A promising growth promoting Meyerozyma caribbica from Solanum xanthocarpum alleviated stress in maize plants

Fungal endophytes are known to secrete a large array of secondary metabolites (phenols, flavonoids, indole acetic acid (IAA) etc.) that facilitate crops under stress conditions. Considering this, a potent plant growth promoting endophyte (SXSp1) from the spines and leaves of Solanum xanthocarpum L. has been isolated. The isolated strain ably secreted high quantities of indole-3-acetic acid, phenols and flavonoids. Also, it exhibited phosphate solubilization, siderophore and had 2,2 diphenyl-1-picrylhydrazyl (DPPH) scavenging activity. The SXSp1 also resisted the salinity stress up to 150 mM. LC/MS analysis of SXSp1 culture filtrate (CF) revealed the presence of p-hydroxyl benzoic acid, diadzein, genistien, myricetin and caffeoyl-d-glucose. Moreover, the inoculation of maize plants with SXSp1 significantly (P=0.05) promoted the chlorophyll and carotenoid contents, root and shoot lengths, plant fresh and dry weights, catalase and peroxidase activities, proline, phenolics, flavonoids and relative water contents (RWCs) under salinity. More interestingly, SXSp1-associated plants showed lower endogenous abscisic acid (ABA) and higher endogenous IAA contents that helped the plants to resist salinity stress up to 100 mM. After sequencing, internal transcribed spacer (ITS) regions (ITS1 and ITS4) and phylogenetic analysis, the SXSp1 was identified as Meyerozyma caribbica.

Natural transformation of the filamentous cyanobacterium Phormidium lacuna

Research for biotechnological applications of cyanobacteria focuses on synthetic pathways and bioreactor design, while little effort is devoted to introduce new, promising organisms in the field. Applications are most often based on recombinant work, and the establishment of transformation can be a risky, time-consuming procedure. In this work we demonstrate the natural transformation of the filamentous cyanobacterium Phormidium lacuna and insertion of a selection marker into the genome by homologous recombination. This is the first example for natural transformation filamentous non-heterocystous cyanobacterium. We found that Phormidium lacuna is polyploid, each cell has about 20-90 chromosomes. Transformed filaments were resistant against up to 14 mg/ml of kanamycin. Formerly, natural transformation in cyanobacteria has been considered a rare and exclusive feature of a few unicellular species. Our finding suggests that natural competence is more distributed among cyanobacteria than previously thought. This is supported by bioinformatic analyses which show that all protein factors for natural transformation are present in the majority of the analyzed cyanobacteria.

Isolation, characterization, and plant growth-promoting activities of endophytic fungi from a wild orchid Vanda cristata

Endophytism is one of the widely explored phenomena related to orchids and fungi. Endophytic fungi assist plants by supplementing nutrient acquisition, and synthesis of plant growth regulators. Vanda cristata is an epiphytic orchid that has a great diversity of endophytic fungi. Endophytic fungi were isolated from roots, stems, and leaves of V.cristata and identified by both morphological and molecular study. Furthermore, the isolated endophytic fungi were subjected to auxin synthesis, phosphate solubilization, ammonia synthesis, and elicitor growth test for understanding their growth-promoting effect in a qualitative and quantitative manner. Altogether, 12 different endophytic fungi were isolated from roots, stems, and leaves of V. cristata of which most species belonged to Ascomycota. Unidentified II fungi were found to be most effective for auxin synthesis and phosphate solubilization while Agaricus bisporous and Mycolepto discus were most effective for ammonia synthesis. We have tested the plant growth-promoting activity of the twelve isolated endophytic fungi on Cymbidium aloifolium protocorms (12 weeks old). All the endophytic fungi showed growth-promoting activity. Plant growth of Cymbidium aloifolium was found higher on the MS medium supplemented with all fungal elicitors. Fungal elicitor CVS4, however, showed the highest plant growth-promoting activity toward C. aloifolium.

Salt stress alleviation in Pennisetum glaucum through secondary metabolites modulation by Aspergillus terreus

The growth promoting activities of the isolated endophyte Aspergillus terreus from Aloe barbendsis was studied in the salt stressed Pennisetum glaucum (pearl millet). A significant (P = 0.05) increase in the root-shoot lengths, fresh and dry weights and chlorophyll content of pearl millet seedlings was noticed after colonization by A. terreus under normal conditions. At 100 mM NaCl stress and A. terreus inoculation, the growth rate of pearl millet seedlings were significantly (P = 0.05) inhibited. Furthermore, the IAA production, relative water content (RWC), chlorophyll, soluble sugar, phenol and flavonoid contents were significantly decreased, whereas proline content and lipid peroxidation were increased. On the contrary, pearl millet seedlings inoculated with A. terreus retained significantly (P = 0.05) higher amounts of RWC, chlorophyll, soluble sugar, phenol and flavonoid contents under 100 mM salt stress. The higher IAA production in A. terreus associated seedlings rescued the plant growth and development under salt stress. Moreover, the LC MS/MS analysis of A. terreus cultural filtrate revealed the presence of quinic acid, ellagic acid, calycosin, wogonin, feruloylquinic acid, caffeic acid phenylethyl ester, D-glucoside, myricetin, propoxyphene and aminoflunitrazepam. The results of the study conclude that innoculation of A. terreus improves the NaCl tolerance in pearl millet by ameliorating the physicochemical attributes of the host plants.

Soil microalgae and cyanobacteria: the biotechnological potential in the maintenance of soil fertility and health

The soil microbiota plays a major role in maintaining the nutrient balance, carbon sink, and soil health. Numerous studies reported on the function of microbiota such as plant growth-promoting bacteria and fungi in soil. Although microalgae and cyanobacteria are ubiquitous in soil, very less attention has been paid on the potential of these microorganisms. The indiscriminate use of various chemicals to enhance agricultural productivity led to serious consequences like structure instability, accumulation of toxic contaminants, etc., leading to an ecological imbalance between soil, plant, and microbiota. However, the significant role of microalgae and cyanobacteria in crop productivity and other potential options has been so far undermined. The intent of the present critical review is to highlight the significance of this unique group of microorganisms in terms of maintaining soil fertility and soil health. Beneficial soil ecological applications of these two groups in enhancing plant growth, establishing interrelationships among other microbes, and detoxifying chemical agents such as insecticides, herbicides, etc. through mutualistic cooperation by synthesizing enzymes and phytohormones are presented. Since recombinant technology involving genomic integration favors the development of useful traits in microalgae and cyanobacteria for their potential application in improvement of soil fertility and health, the merits and demerits of various such advanced methodologies associated in harnessing the biotechnological potential of these photosynthetic microorganisms for sustainable agriculture were also discussed.

Cochliobolus sp. acts as a biochemical modulator to alleviate salinity stress in okra plants

Salinity stress can severely affect the growth and production of the crop plants. Cheap and reliable actions are needed to enable the crop plants to grow normal under saline conditions. Modification at the molecular level to produce resistant cultivars is one of the promising, yet highly expensive techniques, whereas application of endophytes on the other hand are very cheap. In this regard, the role of Cochliobolus sp. in alleviating NaCl-induced stress in okra has been investigated. The growth and biomass yield, relative water content, chlorophyll content and IAA were decreased, whereas malondialdehyde (MDA) and proline content were increased in okra plants treated with 100 mM NaCl. On the contrary, okra plants inoculated with C. lunatus had higher shoot length, root length, plant dry weight, chlorophyll, carotenoids, xanthophyll, phenolicss, flavonoids, IAA, total soluble sugar and relative water content, while lower MDA. LC-MS/MS analysis of the Cochliobolus sp. extract revealed the presence of pinocembrin, chlorogenic acids, wogonin, calycosin and diadzein as a salinity stress reliever. From the results, it can be concluded that colonization of Cochliobolus sp. improves the NaCl tolerance by ameliorating the physicochemical attributes of the host plants.

Cinnamic acid as an inhibitor of growth, flavonoids exudation and endophytic fungus colonization in maize root

Cinnamic acid (CA) is an allelochemical that inhibits the growth of root promoting soil microorganisms. To prevent the growth of soil microbes, CA modulates several metabolic pathways in host plants and soil microbes. The aim of the current study was to investigate the effect of CA on maize root growth, exudation of secondary metabolites and its interaction with beneficial endophyte Pz11. The endophyte Pz11 was isolated from the roots of drought stressed Asphodelus tenuifolius (wild onion). The Pz11 strain was identified as Fusarium culmorum by homology of the internal transcribed spacer (ITS) region of 18 S rDNA sequence. The F. culmorum Pz11 produced phytostimulants and signaling compounds, such as indole-3-acetic acid (IAA), flavonoids and sugars. Moreover, the strain have effectively colonized the roots of maize and subsequently enhanced the growth of its host plants. On the contrary, application of CA has reduced root growth in maize seedlings as well as root colonization ability of F. culmorum Pz11. Also, maize seedlings exposed to CA exude low quantities of flavonoids and polyphenols. In conclusion, CA reduces the maize root growth and exudation of secondary metabolites, which may affects its ability to attract plant growth promoting endophytic fungi.

Endophytic Fungus Aspergillus japonicus Mediates Host Plant Growth under Normal and Heat Stress Conditions

We have isolated an endophytic fungus with heat stress alleviation potential from wild plant Euphorbia indica L. The phylogenetic analysis and 18S rDNA sequence homology revealed that the designated isolate was Aspergillus japonicus EuR-26. Analysis of A. japonicus culture filtrate displayed higher concentrations of salicylic acid (SA), indoleacetic acid (IAA), flavonoids, and phenolics. Furthermore, A. japonicus association with soybean and sunflower had improved plant biomass and other growth features under high temperature stress (40°C) in comparison to endophyte-free plants. In fact, endophytic association mitigated heat stress by negotiating the activities of abscisic acid, catalase, and ascorbic acid oxidase in both soybean and sunflower. The nutritional quality (phenolic, flavonoids, soluble sugars, proteins, and lipids) of the A. japonicus-associated seedlings has also improved under heat stress in comparison to endophyte-free plants. From the results, it is concluded that A. japonicus can modulate host plants growth under heat stress and can be used as thermal stress alleviator in arid and semiarid regions of the globe (where mean summer temperature exceeds 40°C) to sustain agriculture.

Microbial Manipulation of Auxins and Cytokinins in Plants

Microbial associations with plants are crucial for the survival of both the partners. Beside other ways of establishing such associations, phytohormones enjoy a key role in plant-microbe interactions from initial dialog between the two to the establishment of a viable partnership. Cytokinins (CKs) and IAA are among the five classical groups of phytohormones implicated in plant immune response, early signaling, and deciding the fate of interactions between plant and microbes. Here we describe a method to study modulation of Cks and IAA in plant under the influence of a pathogenic bacterium, Pseudomonas syringae tomato DC3000. A method for inoculating bacteria on host plant and subsequent determination of Cks and IAA through HPLC-ESI-MS/MS is described.

Tiny Microbes with a Big Impact: The Role of Cyanobacteria and Their Metabolites in Shaping Our Future

Cyanobacteria are among the first microorganisms to have inhabited the Earth. Throughout the last few billion years, they have played a major role in shaping the Earth as the planet we live in, and they continue to play a significant role in our everyday lives. Besides being an essential source of atmospheric oxygen, marine cyanobacteria are prolific secondary metabolite producers, often despite the exceptionally small genomes. Secondary metabolites produced by these organisms are diverse and complex; these include compounds, such as pigments and fluorescent dyes, as well as biologically-active compounds with a particular interest for the pharmaceutical industry. Cyanobacteria are currently regarded as an important source of nutrients and biofuels and form an integral part of novel innovative energy-efficient designs. Being autotrophic organisms, cyanobacteria are well suited for large-scale biotechnological applications due to the low requirements for organic nutrients. Recent advances in molecular biology techniques have considerably enhanced the potential for industries to optimize the production of cyanobacteria secondary metabolites with desired functions. This manuscript reviews the environmental role of marine cyanobacteria with a particular focus on their secondary metabolites and discusses current and future developments in both the production of desired cyanobacterial metabolites and their potential uses in future innovative projects.