Search

The effects of climate change are becoming increasingly hazardous for our ecosystem. Climate resilient landscaping, which promotes the use of native plants, has the potential to simultaneously decrease the rate of climate change, enhance climate resilience, and combat biodiversity losses. Native plants and their associated microbiome form a holo-organism; interaction between plants and microbes is responsible for plants' growth and proper functioning. In this study, we were interested in exploring the soil and root microbiome composition associated with Shepherdia utahensis, a drought hardy plant proposed for low water use landscaping, which is the hybrid between two native hardy shrubs of Utah, S. rotudifolia and S. argentea. The bulk soil, rhizosphere, root, and nodule samples of the hybrid Shepherdia plants were collected from three locations in Utah: the Logan Campus, the Greenville farm, and the Kaysville farm. The microbial diversity analysis was conducted, and plant growth-promoting bacteria were isolated and characterized from the rhizosphere. The results suggest no difference in alpha diversity between the locations; however, the beta diversity analysis suggests the bacterial community composition of bulk soil and nodule samples are different between the locations. The taxonomic classification suggests Proteobacteria and Actinobacteriota are the dominant species in bulk soil and rhizosphere, and Actinobacteriota is solely found in root and nodule samples. However, the composition of the bacterial community was different among the locations. There was a great diversity in the genus composition in bulk soil and rhizosphere samples among the locations; however, Frankia was the dominant genus in root and nodule samples. Fifty-nine different bacteria were isolated from the rhizosphere and tested for seven plant growth-promoting (PGP) traits, such as the ability to fix nitrogen, phosphates solubilization, protease activity, siderophore, Indole Acetic Acid (IAA) and catalase production, and ability to use ACC as nitrogen source. All the isolates produced some amount of IAA. Thirty-one showed at least four PGP traits and belonged to Stenotrophomonas, Chryseobacterium, Massilia, Variovorax, and Pseudomonas. We shortlisted 10 isolates that showed all seven PGP traits and will be tested for plant growth promotion. [ABSTRACT FROM AUTHOR]

Environmental stress affects food productivity by producing reactive oxygen species (ROS) that damage cell organelles and biomolecules, leading to apoptosis. Plants have developed a variety of defense responses over time to counteract the detrimental effects of biotic and abiotic stresses. However, in order to combat climate change and the deterioration of ecosystems, it will be necessary to promote the use of beneficial bacteria including plant growth-promoting bacteria (PGPR) in agricultural ecosystems. PGPR potentially improves nutrient absorption, modulates hormone levels, and/or improves tolerance to abiotic stress factors and plant pathogens. PGPR offers a sustainable replacement for conventional agrochemicals and traditional farming practices by improving plant growth and stress tolerance. In this context, studying the fundamental evolutionary and ecological relationships among plants and their microbiomes is necessary to build vital approaches to strengthen traditional agricultural techniques. Stress-tolerant PGPR can release bioactive substances such as gibberellins and indole acetic acid which participate in mitigating stresses. PGPR could minimize the adverse effect of salinity, drought, heavy metals, floods, and other stresses on plants by inducing antioxidant enzymes, like catalase, peroxidase, and superoxide dismutase. This review summarizes the current developments in the PGPR-based strategy for tackling biotic and abiotic stresses. [ABSTRACT FROM AUTHOR]

An essential aromatic plant, Pelargonium graveolens, does not grow well in areas where chromium contamination is a problem. Because of oxidative stress and the collapse of the photosynthetic system, crops frequently sustain severe damage. The production of excess ethylene, known as stress ethylene, which is detrimental to plant growth, the formation of roots, and early senescence, is also increased by heavy metal exposure. The effectiveness of the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene in transgenic Pelargonium graveolens under the control of CaMV 35S promoter was investigated to lessen the stress ethylene during chromium stress. Chromium was administered as potassium dichromate (K2Cr2O7) at four distinct concentrations (100 µM, 200 µM, 300 µM, and 500 µM) to transgenic and wild-type P. graveolens and stress-induced physiological changes were monitored. Transgenic P. graveolens demonstrated greater tolerance to chromium stress than wild-type P. graveolens, as evidenced by higher leaf-relative water content, chlorophyll content, CO2 absorption, transpiration rate, stomatal conductance, proline buildup, and antioxidant activity. The L1, L5, and L7, ACC deaminase-expressing transgenic lines also show a drop in ACC content during chromium stress, which subsequently lowered ethylene synthesis. Therefore, the reported transgenic P. graveolens lines having the ACC deaminase gene could be useful resources for growing in chromium-prone regions. [ABSTRACT FROM AUTHOR]

Copyright of Xinjiang Agricultural Sciences is the property of Xinjiang Agricultural Sciences Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bacteria that regulate the growth of plants can be found in many different environments, but they are most commonly found in the rhizosphere. Bacteria in the plant rhizosphere can affect the development of plants in different ways. On the other hand, endophytic bacteria also supported plant growth-promoting activities and showed antagonistic effects, isolated from different plant parts such as roots, stems, branches, leaves, and fruits. In our study, endophytic bacteria isolated from walnut (Juglans regia L.) and olive (Olea purpurea L.) trees, positively affect plant growth as bio-fertilizers. Endophytes were screened for phosphate solubilization, indole-3-acetic acid (IAA), ammonia, siderophore, hydrogen cyanide, protease enzyme, chitinase enzyme, and ACC deaminase production capabilities. Whether endophytic bacteria have bio-protective properties against different pathogen groups had been tested on Verticillium dahliae (fungal wilt), Pseudomonas savastanoi pv. glycinea (bacterial blight), and Xanthomonas campestris pv. vesicatoria (bacterial blight). Potential bio-fertilizer and bio-protective bacteria identified according to their fatty acids and 16S rRNA gene regions. Members of the genus Pseudomonas, Bacillus, Brevibacillus, Paenibacillus, Staphylococcus, Pantoea, and Serratia were endophytically found in different plants parts. Following rapid plant growth-promoting trait tests, twelve bacteria were used for the hydroponic germination of wheat seedlings (Triticum aestivum L.). Eight improved wheat root and stem growth and six had statistically (p < 0.05) positive effects compared to non-bacteria-treated seedlings. [ABSTRACT FROM AUTHOR]

Abstract Salinity impacts crop growth and productivity and lowers the activities of rhizosphere microbiota. The identification and utilization of habitat-specific salinity-adapted plant growth-promoting rhizobacteria (PGPR) are considered alternative strategies to improve the growth and yields of crops in salinity-affected coastal agricultural fields. In this study, we characterize strain L1I39T, the first Aquabacter species with PGPR traits isolated from a salt-tolerant pokkali rice cultivated in brackish environments. L1I39T is positive for 1-aminocyclopropane-1-carboxylate deaminase activity and nitrogen fixation and can promote pokkali rice growth by supplying fixed nitrogen under a nitrogen-deficient seawater condition. Importantly, enhanced plant growth and efficient root colonization were evident in L1I39T-inoculated plants grown under 20% seawater but not in zero-seawater conditions, identifying brackish conditions as a key local environmental factor critical for L1I39T-pokkali rice symbiosis. Detailed physiological studies revealed that L1I39T is well-adapted to brackish environments. In-depth genome analysis of L1I39T identified multiple gene systems contributing to its plant-associated lifestyle and brackish adaptations. The 16S rRNA-based metagenomic study identified L1I39T as an important rare PGPR taxon. Based on the polyphasic taxonomy analysis, we established strain L1I39T as a novel Aquabacter species and proposed Aquabacter pokkalii sp nov. Overall, this study provides a better understanding of a marine-adapted PGPR strain L1I39T that may perform a substantial role in host growth and health in nitrogen-poor brackish environments.

Salinity impacts crop growth and productivity and lowers the activities of rhizosphere microbiota. The identification and utilization of habitat-specific salinity-adapted plant growth-promoting rhizobacteria (PGPR) are considered alternative strategies to improve the growth and yields of crops in salinity-affected coastal agricultural fields. In this study, we characterize strain L1I39T, the first Aquabacter species with PGPR traits isolated from a salt-tolerant pokkali rice cultivated in brackish environments. L1I39T is positive for 1-aminocyclopropane-1-carboxylate deaminase activity and nitrogen fixation and can promote pokkali rice growth by supplying fixed nitrogen under a nitrogen-deficient seawater condition. Importantly, enhanced plant growth and efficient root colonization were evident in L1I39T-inoculated plants grown under 20% seawater but not in zero-seawater conditions, identifying brackish conditions as a key local environmental factor critical for L1I39T-pokkali rice symbiosis. Detailed physiological studies revealed that L1I39T is well-adapted to brackish environments. In-depth genome analysis of L1I39T identified multiple gene systems contributing to its plant-associated lifestyle and brackish adaptations. The 16S rRNA-based metagenomic study identified L1I39T as an important rare PGPR taxon. Based on the polyphasic taxonomy analysis, we established strain L1I39T as a novel Aquabacter species and proposed Aquabacter pokkalii sp nov. Overall, this study provides a better understanding of a marine-adapted PGPR strain L1I39T that may perform a substantial role in host growth and health in nitrogen-poor brackish environments. [ABSTRACT FROM AUTHOR]

The present study focuses on the 1‐aminocyclopropane‐1‐carboxylic acid (ACC) deaminase assay and the rhizospheric interactions affecting enzyme activity. We investigate the efficacy of ACC deaminase‐producing rhizobacterial activity in alleviating salt stress in rice. Among the five selected isolates, only two strains, KFSC2 and PK7, possessed the enzyme activity. The amplification of the acdS gene resulted in gene identification in all five isolates. The newly designed primer in this study was suitable for both Pseudomonas and Enterobacter species. The gene products of KFSC1 and KFSC2 were amplified, sequenced and subsequently submitted to GenBank with accession numbers OQ703930 and OQ798805, respectively. This marks the first‐ever submission of the acdS gene sequence from Pseudomonas aeruginosa to GenBank. The interactive effect of root exudates on ACC deaminase activity was assessed using amino acids, organic acids and sugars. The highest enzyme activity was obtained with aspartic acid and fructose, while organic acids and varying pH levels had negative influences on enzyme activity. Additionally, salt and proline had positive effects. These results indicate that there is a positive interaction occurring among these compounds from plants and root‐colonizing bacteria. The selected strain PK7 had a significant impact on growth parameters. Moreover, yield resulted in 252 kg/hec over the control suggests its future possibility of promising bioformulations. [ABSTRACT FROM AUTHOR]

Abiotic and biotic stresses adversely impact the growth and productivity of the crops globally. Stressful environmental conditions affect the plants morphological and physiological characteristics. Increase in the ethylene production and its inhibitory effect on root development is one of the major challenges under stressed conditions. The association of the beneficial microbiomes with the plants plays a substantial role in improving the health and productivity under the stressful circumstances. Plant growth-promoting (PGP) microbiomes have inherent capabilities of supporting plant growth and development under different environmental conditions by different mechanisms. ACC (1-aminocyclopropane-1-carboxylate) deaminase production is an imperative trait of PGP microbiome for lowering the inhibitory concentrations of ethylene. ACC deaminase producing microbes thus allows the plants to better cope up with the stressed conditions. The ACC deaminase producing belong domains bacteria, and eukarya. The strains belonging to the genera Azospirillum, Bacillus, Brevundimonas, Hallobacillus, Paenibacillus, Providencia, Pseudomonas, Psychrobacter, Serratia, Stenotrophomonas, and Streptomyces laurentii have been reported as efficient and potential ACC deaminase producers. Looking forward the benefits of ACC deaminase producing PGP microbes with multiple PGP plant growth-promoting attributes as bioinoculants to protect plants from harsh environmental conditions make them a viable tool. [ABSTRACT FROM AUTHOR]

Insights into plant and bacterial associations, along with their genome mining, have paved the way for the improvement of the agriculture sector. Initially, 69 morphologically different bacterial strains were isolated from 6 different extreme environment samples. For in vitro screening of plant growth-promoting bacteria, auxin, hydrogen cyanide, and antibiotic production along with phosphate solubilization potential was estimated. Only 15 strains exhibited noteworthy production of plant growth-promoting compounds. Ochrobactrum ciceri CS-10 fostered Triticum aestivum and Zea mays seedling root growth remarkably (104.12 and 159%, respectively), while Bacillus australimaris TP-10 significantly increased the number of leaves in T. aestivum (166.66%) and Z. mays (133.33%) seedlings. These strains also boosted seedling biochemical traits, like indole acetic acid, peroxidase, and soluble protein content. Particularly, O. ciceri elevated peroxidase content greatly in T. aestivum (249.7%) and Z. mays (260.5%). Scanning electron micrographs of inoculated roots revealed the aggregation of cells at the roots of Z. mays, whereas single cells/micro-colonies were observed on T. aestivum roots. For in silico analysis, AntiSMASH was used for genome mining of the environmental Ochrobactrum sp. and B. australimaris reference genome. This genome mining unveiled diverse gene clusters encoding; terpenes, beta-lactones, acyl-amino-acids, aryl polyenes, lanthipeptide, and siderophores, etc. Two common biosynthetic gene clusters (terpenes and beta-lactones) were identified in these strains, which can act as plant growth promoters. This symbiotic plant–bacteria relationship has promising ecological and economic implications, offering avenues for beneficial applications.

Soil salinity is one of the major environmental stresses that results in reduction of cultivable land and decreased productivity. In the present study, halotolerant and plant growth-promoting endophytic fungi were isolated from Catharanthus roseus, and their e ect in mitigating salt stress in Vigna radiata was evaluated. An isolate CR7, identified to be Aspergillus terreus, showing plant growth promotion activities, viz. IAA production (23.43 ± 0.79 µg/ml), phosphate solubilization (133.63 ± 6.40 µg/ml), ACC deaminase activity (86.36 ± 2.70 µmol α-ketobutyrate/h/mg protein) etc. and ability to grow at 15% NaCl was selected for further in vivo studies. Colonization of CR7 was carried out in V. radiata which was subjected to di erent concentrations of salt (150, 200, and 250 mM NaCl). Under salt stress, A. terreus CR7 inoculated plants showed substantially improved root and shoot length, biomass, chlorophyll content, relative water content, phenolics, protein content, and DPPH scavenging activity. Endogenous IAA level was enhanced by 5.28-fold in treated plants at maximum salt stress. Inoculation of A. terreus CR7 a ected oxidative stress parameters, exhibiting an increase in catalase and superoxide dismutase and reduction in proline, electrolyte leakage, and malondialdehyde content. Fluorescent microscopic analysis of roots revealed improved cell viability and decreased levels of glutathione and hydrogen peroxide under salt stress in treated plants. The isolate A. terreus CR7 also protected against DNA damage induced by salt stress which was evaluated using comet assay. A decrease in DNA tail length, tail moment, and olive tail moment to the extent of 19.87%, 19.76%, and 24.81%, respectively, was observed in A. terreus CR7-colonized plants under salt stress. It can be concluded that A. terreus CR7 can be exploited for alleviating the impact of salt stress in crop plants. [ABSTRACT FROM AUTHOR]

Copyright of BIOAGRO is the property of Revista BIOAGRO and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACTCodonopsis pilosula is a perennial herbaceous liana with medicinal value. It is critical to promote Codonopsis pilosula growth through effective and sustainable methods, and the use of plant growth-promoting bacteria (PGPB) is a promising candidate. In this study, we isolated a PGPB, Klebsiella michiganensis LDS17, that produced a highly active 1-aminocyclopropane-1-carboxylate deaminase from the Codonopsis pilosula rhizosphere. The strain exhibited multiple plant growth-promoting properties. The antagonistic activity of strain LDS17 against eight phytopathogenic fungi was investigated, and the results showed that strain LDS17 had obvious antagonistic effects on Rhizoctonia solani, Colletotrichum camelliae, Cytospora chrysosperma, and Phomopsis macrospore with growth inhibition rates of 54.22%, 49.41%, 48.89%, and 41.11%, respectively. Inoculation of strain LDS17 not only significantly increased the growth of Codonopsis pilosula seedlings but also increased the invertase and urease activities, the number of culturable bacteria, actinomycetes, and fungi, as well as the functional diversity of microbial communities in the rhizosphere soil of the seedlings. Heavy metal (HM) resistance tests showed that LDS17 is resistant to copper, zinc, and nickel. Whole-genome analysis of strain LDS17 revealed the genes involved in IAA production, siderophore synthesis, nitrogen fixation, P solubilization, and HM resistance. We further identified a gene (koyR) encoding a plant-responsive LuxR solo in the LDS17 genome. Klebsiella michiganensis LDS17 may therefore be useful in microbial fertilizers for Codonopsis pilosula. The identification of genes related to plant growth and HM resistance provides an important foundation for future analyses of the molecular mechanisms underlying the plant growth promotion and HM resistance of LDS17.IMPORTANCEWe comprehensively evaluated the plant growth-promoting characteristics and heavy metal (HM) resistance ability of the LDS17 strain, as well as the effects of strain LDS17 inoculation on the Codonopsis pilosula seedling growth and the soil qualities in the Codonopsis pilosula rhizosphere. We conducted whole-genome analysis and identified lots of genes and gene clusters contributing to plant-beneficial functions and HM resistance, which is critical for further elucidating the plant growth-promoting mechanism of strain LDS17 and expanding its application in the development of plant growth-promoting agents used in the environment under HM stress.

Drought stress severely affects the physiology and metabolism of plants. Fortunately, using plant growth-promoting bacteria can provide an environmentally friendly solution. Hence, the present experiment was conducted on the sorghum plant for drought amelioration by utilizing Bacillus sp. and Pseudacidovorax intermedius bacterization to the sorghum seeds under greenhouse conditions. Drought stress was induced by the withholding of water after 52 days of emergence (flowering stage). However, the inoculation of Bacillus sp. and Pseudacidovorax intermedius could significantly improve the drought tolerance capacity through the production of different antioxidant enzymes and metabolites in sorghum plants under drought and recovery conditions. The results declared that the inoculation of Bacillus sp. significantly reduced the membrane leakage by 37 % by minimizing the production of malondialdehyde (49 & 47 %) and hydrogen peroxide (32 & 36 %) content. In addition to protecting membrane leakage, bacterial inoculation positively modulates the antioxidant enzymes namely catalase, ascorbate peroxidase, glutathione peroxidase, superoxide dismutase, and phenol content in the plant system. Metabolomic results revealed that inoculation of Bacillus sp. and consortia of Bacillus sp. and Pseudacidovorax intermedius up regulate the carboxylic acid, organic, and amino acids biomolecules expression inside the inoculated plants. The study concluded that inoculation of Bacillus sp. is an assured technology for mitigating the drought effect through the expression of antioxidant compounds, and expression of leaf metabolites in sorghum during drought conditions. Further, the research needs to comprehend the underlying molecular mechanism of bacterial-induced drought-tolerant in sorghum plants. It will also create a road map to develop a bestselling bioinoculant for climate-smart agriculture.

Soil salinity is one of the major environmental stresses that results in reduction of cultivable land and decreased productivity. In the present study, halotolerant and plant growth-promoting endophytic fungi were isolated from Catharanthus roseus, and their effect in mitigating salt stress in Vigna radiata was evaluated. An isolate CR7, identified to be Aspergillus terreus, showing plant growth promotion activities, viz. IAA production (23.43 ± 0.79 μg/ml), phosphate solubilization (133.63 ± 6.40 μg/ml), ACC deaminase activity (86.36 ± 2.70 μmol α-ketobutyrate/h/mg protein) etc. and ability to grow at 15% NaCl was selected for further in vivo studies. Colonization of CR7 was carried out in V. radiata which was subjected to different concentrations of salt (150, 200, and 250 mM NaCl). Under salt stress, A. terreus CR7 inoculated plants showed substantially improved root and shoot length, biomass, chlorophyll content, relative water content, phenolics, protein content, and DPPH scavenging activity. Endogenous IAA level was enhanced by 5.28-fold in treated plants at maximum salt stress. Inoculation of A. terreus CR7 affected oxidative stress parameters, exhibiting an increase in catalase and superoxide dismutase and reduction in proline, electrolyte leakage, and malondialdehyde content. Fluorescent microscopic analysis of roots revealed improved cell viability and decreased levels of glutathione and hydrogen peroxide under salt stress in treated plants. The isolate A. terreus CR7 also protected against DNA damage induced by salt stress which was evaluated using comet assay. A decrease in DNA tail length, tail moment, and olive tail moment to the extent of 19.87%, 19.76%, and 24.81%, respectively, was observed in A. terreus CR7-colonized plants under salt stress. It can be concluded that A. terreus CR7 can be exploited for alleviating the impact of salt stress in crop plants.

We overexpressed the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene (acdS), which encodes the enzyme responsible for the degradation of an ethylene precursor (ACC), in Petunia hybrida cv. Mirage Rose. We investigated whether acdS overexpression rendered the petunia more tolerant to copper (Cu) stress. The transgenic plants exhibited greater tolerance to Cu stress than wild type (WT) plants, as evidenced by better plant growth and physiological performances. Additionally, the transgenic plants displayed significantly suppressed ethylene production and related genes, elevated expression of antioxidant and proline activity-related genes, reduced accumulation of reactive oxygen species and Cu, and increased expression of genes regulating heavy metal when compared to the WT plants. These findings elucidate the mechanism by which acdS imparts Cu stress tolerance, suggesting that overexpressing acdS in plants can facilitate their resilience to Cu stress.

Modern technologies can satisfy human needs only with the use of large quantities of fertilizers and pesticides that are harmful to the environment. For this reason, it is possible to develop new technologies for sustainable agriculture. The process could be carried out by using endophytic microorganisms with a (possible) positive effect on plant vitality. Bacterial endophytes have been reported as plant growth promoters in several kinds of plants under normal and stressful conditions. In this study, isolates of bacterial endophytes from the roots and leaves of Miscanthus giganteus plants were tested for the presence of plant growth-promoting properties and their ability to inhibit pathogens of fungal origin. Selected bacterial isolates were able to solubilize inorganic phosphorus, fix nitrogen, and produce phytohormones, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and siderophore. Leaf bacterial isolate Pantoea ananat is 50 OL 2 had high production of siderophores (zone ≥ 5 mm), and limited phytohormone production, and was the only one to show ACC deaminase activity. The root bacterial isolate of Pseudomonas libanensis 5 OK 7A showed the best results in phytohormone production (N6-(Δ2-isopentenyl)adenine and indole-3-acetic acid, 11.7 and 12.6 ng·mL−1, respectively). Four fungal cultures—Fusarium sporotrichioides DBM 4330, Sclerotinia sclerotiorum SS-1, Botrytis cinerea DS 90 and Sphaerodes fimicola DS 93—were used to test the antifungal activity of selected bacterial isolates. These fungal cultures represent pathogenic families, especially for crops. All selected root endophyte isolates inhibited the pathogenic growth of all tested fungi with inhibition percentages ranging from 30 to 60%. Antifungal activity was also tested in two forms of immobilization of selected bacterial isolates: one in agar and the other on dextrin-coated cellulose carriers. These results demonstrated that the endophytic Pseudomonas sp. could be used as biofertilizers for crops. [ABSTRACT FROM AUTHOR]

Salt stress and drought stress can decrease the growth and productivity of agricultural crops. Plant growth-promoting bacteria (PGPB) may protect and promote plant growth at abiotic stress. The aim of this study was to search for bacterial strains that can help crops resist rises in drought and salt stresses, to improve crop seed resistance under drought and salt stresses, and to investigate the effect of bacterial strains that can help crop resist external stresses under different stress conditions. Pseudomonas DY1-3, a strain from the soil under the glacier moss community of Tien Shan No. 1, was selected to investigate its growth-promoting effects. Previous studies have shown that this strain is capable of producing ACC (1-aminocyclopropane-1-carboxylic acid) deaminase. In this experiment, multifunctional biochemical test assays were evaluated to determine their potential as PGPB and their bacterial growth-promoting properties and stress-resistant effects on maize plants were verified through seed germination experiments and pot experiments. The results showed that strain DY1-3 has good salt and drought tolerance, as well as the ability to melt phosphorus, fix nitrogen, and produce iron carriers, IAA, EPS, and other pro-biomasses. This study on the growth-promoting effects of the DY1-3 bacterial strain on maize seeds revealed that the germination rate, primary root length, germ length, number of root meristems, and vigor index of the maize seeds were increased after soaking them in bacterial solution under no-stress, drought-stress, and salt-stress environments. In the potting experiments, seedlings in the experimental group inoculated with DY1-3 showed increased stem thicknesses, primary root length, numbers of root meristems, and plant height compared to control seedlings using sterile water. In the study on the physiological properties of the plants related to resistance to stress, the SOD, POD, CAT, and chlorophyll contents of the seedlings in the experimental group, to which the DY1-3 strain was applied, were higher than those of the control group of seedlings to which the bacterial solution was not applied. The addition of the bacterial solution reduced the content of MDA in the experimental group seedlings, which indicated that DY1-3 could positively affect the promotion of maize seedlings and seeds against abiotic stress. In this study, it was concluded that strain DY1-3 is a valuable strain for application, which can produce a variety of pro-biotic substances to promote plant growth in stress-free environments or to help plants resist abiotic stresses. In addition to this, the strain itself has good salt and drought tolerance, making it an option to help crops grown in saline soils to withstand abiotic stresses, and a promising candidate for future application in agricultural biofertilizers. [ABSTRACT FROM AUTHOR]

Plants exposed to abiotic stress such as drought and salinity produce 1-aminocyclopropane-1-carboxylic acid (ACC) that is converted into the stress hormone ethylene. However, plant growth-promoting bacteria (PGPB), which synthesize the enzyme ACC deaminase, may lower the ACC concentration thereby reducing the concentration of ethylene and alleviating the abiotic stress. The PGPB Pseudomonas hormoni G20-18T (previously named P. fluorescens G20-18) harbors the genes acdR and acdS that encode regulation and synthesis of ACC deaminase, respectively. Regulation of the acdS gene has been investigated in several studies, but so far, it has been an open question whether plants can regulate microbial synthesis of ACC deaminase. In this study, small molecules in wheat root exudates were identified using untargeted metabolomics, and compounds belonging to amino acids, organic acids, and sugars were selected for evaluation of their influence on the expression of the acdS and acdR genes in P. hormoni G20-18T. acdS and acdR promoters were fused to the fluorescence reporter gene mCherry enabling the study of acdS and acdR promoter activity. In planta studies in wheat seedlings indicated an induced expression of acdS in association with the roots. Exudate molecules such as aspartate, alanine, arginine, and fumarate as well as glucose, fructose, and mannitol actively induced the acdS promoter, whereas the plant hormone indole-3-acetic acid (IAA) inhibited expression. Here, we present a model for how stimulatory and inhibitory root exudate molecules influence acdS promoter activity in P. hormoni G20-18T. [ABSTRACT FROM AUTHOR]

Microbes enhance crop resilience to abiotic stresses, aiding agricultural sustainability amid rising global land salinity. While microbes have proven effective via seed priming, soil amendments, and foliar sprays in diverse crops, their mechanisms remain less explored. This study explores the utilization of ACC deaminase-producing Nocardioides sp. to enhance wheat growth in saline environments and the molecular mechanisms underlying Nocardioides sp.-mediated salinity tolerance in wheat. The Nocardioides sp. inoculated seeds were grown under four salinity regimes viz., 0 dS m−1, 5 dS m−1, 10 dS m−1, and 15 dS m−1, and vegetative growth parameters including shoot-root length, germination percentage, seedling vigor index, total biomass, and shoot-root ratio were recorded. The Nocardioides inoculated wheat plants performed well under saline conditions compared to uninoculated plants and exhibited lower shoot:root (S:R) ratio (1.52 ± 0.14 for treated plants against 1.84 ± 0.08 for untreated plants) at salinity level of 15 dS m−1 and also showed improved biomass at 5 dS m−1 and 10 dS m−1. Furthermore, the inoculated plants also exhibited higher protein content viz., 22.13 mg g−1, 22.10 mg g−1, 22.63 mg g−1, and 23.62 mg g−1 fresh weight, respectively, at 0 dS m−1, 5 dS m−1, 10 dS m−1, and 15 dS m−1. The mechanisms were studied in terms of catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase activity, free radical scavenging potential, in-situ localization of H2O2 and superoxide ions, and DNA damage. The inoculated seedlings maintained higher enzymatic and non-enzymatic antioxidant potential, which corroborated with reduced H2O2 and superoxide localization within the tissue. The gene expression profiles of 18 stress-related genes involving abscisic acid signaling, salt overly sensitive (SOS response), ion transporters, stress-related transcription factors, and antioxidant enzymes were also analyzed. Higher levels of stress-responsive gene transcripts, for instance, TaABARE (~+7- and +10-fold at 10 dS m−1 and 15 dS m−1); TaHAk1 and hkt1 (~+4- and +8-fold at 15 dS m−1); antioxidant enzymes CAT, MnSOD, POD, APX, GPX, and GR (~+4, +3, +5, +4, +9, and +8 folds and), indicated actively elevated combat mechanisms in inoculated seedlings. Our findings emphasize Nocardioides sp.–mediated wheat salinity tolerance via ABA-dependent cascade and salt-responsive ion transport system. This urges additional study of methylotrophic microbes to enhance crop abiotic stress resilience. [ABSTRACT FROM AUTHOR]

Climate change and global warming are leading to severe drought stress, causing damage to crops in different regions of the world. Drought stress is an abiotic stress that interferes with major metabolic pathways, influencing mainly morphological, physiological and biochemical parameters of plants, ultimately resulting in decreased growth and yield of crops. Plants should be able to utilise available moisture efficiently, and there is a need to focus on organic and eco-friendly methods for improving crops facing drought stress. A practical approach for enhancing growth and development under stressful conditions is the application of plant growth promoting rhizobacteria (PGPR), soil microbes that help plants to cope with extreme ecological conditions. This review aims to highlight the function of various PGPR metabolites that help to mitigate water-deficit conditions. These microbes exist naturally in the rhizosphere of plants, and they enhance plant growth by several direct mechanisms such as aminocyclopropane-1-carboxylate deaminase and osmolyte production, secretion of exopolysaccharides and phytohormones, triggering of antioxidant defence mechanisms against reactive oxygen species and production of volatile organic compounds, as well as by indirect mechanisms including enhancing induced systemic resistance and pathogen suppression. This review recommends the use of PGPR for improving growth and development of crops under drought stress and supports their role as effective and sustainable bioinoculants for enhancing the growth and production of crops. This review aims to highlight the function of various metabolites produced by plant growth promoting rhizobacteria (PGPR) that can help in mitigating water-deficit conditions in crops. PGPR are microbes that naturally exist in the rhizosphere of plants and enhance plant growth by several direct and indirect mechanisms including production of aminocyclopropane-1-carboxylate deaminase, osmolytes and volatiles, secretion of exopolysaccharides and phytohormones, triggering of antioxidant defence mechanisms, enhancing induced systemic resistance and pathogen suppression. [ABSTRACT FROM AUTHOR]

Plant growth promoting rhizobacteria (PGPR) have the potential to promote plant growth under extreme environmental conditions. The purposes of the present study were first to isolate and identify drought tolerant ACC deaminase producing PGPR from rhizosphere soil of cluster bean (Cyamopsis tetragonoloba), and second to study the effect of selected bacterial isolates on plant growth, nodulation and soil properties of cluster bean under drought. Rhizosphere bacterial isolates were tested for their drought tolerance ability, ACC deaminase activity and other PGP attributes such as the production of indole-3-acetic acid (IAA), ammonia, HCN, siderophore and phosphate solubilization. The selected isolates were identified by 16S rRNA sequencing analysis. These selected isolates were further evaluated for plant growth promoting traits and other attributes, such as ethylene emission, osmolytes accumulation, nutrients uptake, soil nutrient availability and soil enzymes activities under drought stress. Three isolates were positive for ACC deaminase activity and identified as Bacillus sonoresis (KM1), Psuedomonas stutzeri (AK17) and Paenibacillus polymyxa (KM6). Under drought stress, inoculation with AK17 and KM6 isolates significantly improved plant growth, RWC and lowered the ethylene emission as compared to uninoculated plants. These isolate also helped in mitigating the adverse effects of drought stress in Cyamopsis by enhancing the accumulation of proline, glycine betaine and decreasing lipid peroxidation. Availability of soil nutrients and soil enzymes activities were also increased in treated plants. These findings show that isolates AK17 and KM6 helps in improving tolerance of cluster bean seedling and can act as potent bioinoculants for crops cultivated under water-stressed conditions. [ABSTRACT FROM AUTHOR]

The ability of microorganisms to promote plant growth and mitigate abiotic and biotic stresses makes them an interesting tool for sustainable agriculture. Numerous studies aim to identify new, promising bacteria isolates. Traditional culture-based methods, which focus on selecting microorganisms with plant-growth-promoting traits, such as hormone production, nutrient solubilization, and antifungal properties, are widely used. This study aims to investigate the role of plant-growth-promoting properties in bacteria-mediated stress mitigation and the suitability of traditional culture-based methods as a screening tool for the identification of beneficial bacteria. To this end, we tested three endophytic Bacillus isolates, which have previously been shown to affect tolerance against iron toxicity in lowland rice, (a) for their effect on the resistance against brown spot disease, and (b) for plant-growth-promoting traits using common culture-based methods. Both B. pumilus isolates inhibited fungal growth in vitro and reduced brown spot disease in two of three rice cultivars in planta, although they tested negative for all plant-growth-promoting traits. While B. megaterium was negative for ACC deaminase activity and nutrient solubilization, it exhibited auxin production. Nevertheless, B. megaterium did not suppress brown spot disease in any of the three rice cultivars. This study shows that bacteria do not necessarily have to possess classical plant-growth-promoting properties in order to be beneficial to plants, and it emphasizes the limitation of common culture-based methods in effectively identifying beneficial bacteria. Moreover, our results highlight the significance of the interaction between bacteria and plant cultivars in determining the beneficial effects of Bacillus spp. on plants under biotic or abiotic stresses. [ABSTRACT FROM AUTHOR]

Microbes enhance crop resilience to abiotic stresses, aiding agricultural sustainability amid rising global land salinity. While microbes have proven effective via seed priming, soil amendments, and foliar sprays in diverse crops, their mechanisms remain less explored. This study explores the utilization of ACC deaminase-producing Nocardioides sp. to enhance wheat growth in saline environments and the molecular mechanisms underlying Nocardioides sp.-mediated salinity tolerance in wheat. The Nocardioides sp. inoculated seeds were grown under four salinity regimes viz., 0 dS m−1, 5 dS m−1, 10 dS m−1, and 15 dS m−1, and vegetative growth parameters including shoot-root length, germination percentage, seedling vigor index, total biomass, and shoot-root ratio were recorded. The Nocardioides inoculated wheat plants performed well under saline conditions compared to uninoculated plants and exhibited lower shoot:root (S:R) ratio (1.52 ± 0.14 for treated plants against 1.84 ± 0.08 for untreated plants) at salinity level of 15 dS m−1 and also showed improved biomass at 5 dS m−1 and 10 dS m−1. Furthermore, the inoculated plants also exhibited higher protein content viz., 22.13 mg g−1, 22.10 mg g−1, 22.63 mg g−1, and 23.62 mg g−1 fresh weight, respectively, at 0 dS m−1, 5 dS m−1, 10 dS m−1, and 15 dS m−1. The mechanisms were studied in terms of catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase activity, free radical scavenging potential, in-situ localization of H2O2 and superoxide ions, and DNA damage. The inoculated seedlings maintained higher enzymatic and non-enzymatic antioxidant potential, which corroborated with reduced H2O2 and superoxide localization within the tissue. The gene expression profiles of 18 stress-related genes involving abscisic acid signaling, salt overly sensitive (SOS response), ion transporters, stress-related transcription factors, and antioxidant enzymes were also analyzed. Higher levels of stress-responsive gene transcripts, for instance, TaABARE (~+7- and +10-fold at 10 dS m−1 and 15 dS m−1); TaHAk1 and hkt1 (~+4- and +8-fold at 15 dS m−1); antioxidant enzymes CAT, MnSOD, POD, APX, GPX, and GR (~+4, +3, +5, +4, +9, and +8 folds and), indicated actively elevated combat mechanisms in inoculated seedlings. Our findings emphasize Nocardioides sp.–mediated wheat salinity tolerance via ABA-dependent cascade and salt-responsive ion transport system. This urges additional study of methylotrophic microbes to enhance crop abiotic stress resilience.

Pogostemon cablin cultivation faces massive constraints because of its susceptability to drought stress that reduces patchouli propagation and oil yield. The present study has achieved an efficient and rapid direct regeneration system for the transgenic production of P. cablin using Agrobacterium-mediated genetic transformation. To establish an efficient regeneration protocol for fast in-vitro multiplication of patchouli plants, leaf, petiole, and transverse thin cell layer (tTCL) explants were used and inoculated on an MS medium supplemented with different combinations of phytohormones. A comparative study showed a maximum regeneration frequency of 93.30 ± 0.56% per explant was obtained from leaf segments on optimal MS medium fortified with 0.2mg/L BAP and 0.1mg/L NAA. Leaf and petiole explants took 25-35 days to regenerate while tTCL section showed regeneration in just 15-20 days on the same medium. Subsequently, productive genetic transformation protocol OD600 0.6, AS 200µM, 30mg/L kanamycin, and infection time 5 min. was standardized and best-suited explants were infected at optimum conditions from the Agrobacterium tumefaciens (LBA 4404) strain harboring ACC deaminase to generate transgenic P. cablin Benth. (CIM-Samarth) plants. The investigation suggested that the optimized protocol provides a maximum transformation frequency of 42 ± 1.9% in 15-20 days from tTCL. The transgenic plants were shifted to the greenhouse with a 52.0 ± 0.8% survival frequency. A molecular docking study confirmed significant binding affinity of ligand ACC with ACC deaminase at the catalytic site, and ligand interactions showed four H-bonds at the binding pocket with amino acids Cys-196, Val-198, Thr-199, and Gly-200 that validate gene relative expression in transgenic plants. Among all transgenic acclimatized greenhouse-grown patchouli plants, line PT4 showed improved drought resistance under severe water stress as its RWC was 71.7 ± 2.3% to 75.7 ± 2.1% which is greater than the RWC of the control plant, 58.30 ± 0.21%. Analysis of the other physiological indicators, H2O2, chlorophyll content, and ROS result support drought resistance ability. Our study concluded that the first report on P. cablin, tTCL direct regeneration, and standardized transformation protocol created a new opportunity for genetic manipulation to achieve droughtresistant patchouli plants for cultivation in all seasons at the commercial level. [ABSTRACT FROM AUTHOR]

Simple Summary: The molecule 1-aminocyclopropane-1-carboxylate is the immediate precursor of the plant hormone ethylene in most seed plant species. Both 1-aminocyclopropane-1-carboxylate and ethylene can affect plant growth and development in a variety of ways. In addition, the bacterial enzyme 1-aminocyclopropane-1-carboxylate deaminase can cleave 1-aminocyclopropane-1-carboxylate and prevent both 1-aminocyclopropane-1-carboxylate and ethylene from affecting plant gene expression and subsequent behavior. In this review, the roles of 1-aminocyclopropane-1-carboxylate, ethylene and 1-aminocyclopropane-1-carboxylate deaminase in the development of plants and their regulation are explored. Since D-amino acids stimulate ethylene synthesis in plants, a section of the review is dedicated to this topic. It is suggested that 1-aminocyclopropane-1-carboxylate was synthesized in plants prior to the plant synthesis of ethylene, giving 1-aminocyclopropane-1-carboxylate some control of plant gene expression in response to environmental signals. Here, a brief summary of the biosynthesis of 1-aminocyclopropane-1-carboxylate (ACC) and ethylene in plants, as well as overviews of how ACC and ethylene act as signaling molecules in plants, is presented. Next, how the bacterial enzyme ACC deaminase cleaves plant-produced ACC and thereby decreases or prevents the ethylene or ACC modulation of plant gene expression is considered. A detailed model of ACC deaminase functioning, including the role of indoleacetic acid (IAA), is presented. Given that ACC is a signaling molecule under some circumstances, this suggests that ACC, which appears to have evolved prior to ethylene, may have been a major signaling molecule in primitive plants prior to the evolution of ethylene and ethylene signaling. Due to their involvement in stimulating ethylene production, the role of D-amino acids in plants is then considered. The enzyme D-cysteine desulfhydrase, which is structurally very similar to ACC deaminase, is briefly discussed and the possibility that ACC deaminase arose as a variant of D-cysteine desulfhydrase is suggested. [ABSTRACT FROM AUTHOR]

Background: Bacterial endophytes lives in internal tissues of root, stem and leaves of grain amaranth plants. Isolation and screening of efficient bacterial endophytes for plant growth promotion, biocontrol activities and drought tolerance can develop as suitable bioinoculants for alleviate drought and stress tolerance and plant growth promotion. Methods: Bacterial endophytes were isolated from grain amaranth (Amaranthus spp) and all isolates were screened for nitrogen fixation, phosphorous solubilisation, growth hormone production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase production. Molecular identification of bacterial isolates was done by 16S rRNA sequencing to identify the organisms. Result: Seventeen isolates showed high growth in N-free media and nine isolates could efficiently solubilize phosphates. Two isolates significantly produced higher concentrations of gibberellins, maximum number of bacterial isolates produced Indole-3-acetic acid (IAA) and eight isolates were able to produce cytokinins. Fifteen isolates have shown positive for ACC activity [1-Aminocyclopropane- 1-carboxylate (ACC) deaminase production] in grain amaranth and five bacterial isolates (RAR-5, RAS-3, RAL-7, WAR-1 and WAS-11) have significant plant growth promoting activities compared to others. Further, significant bacterial isolates were identified as Alcaligenes faecalis subsp. phenolicus, Pseudomonas moorei, Bacillus siamensis, Bacillus cereus and Acromobacter deleyi by 16S rRNA gene sequencing. [ABSTRACT FROM AUTHOR]

Various abiotic stresses affect plants in the environment, and the impact may be impaired by global climate change soon. Plants produce ethylene in response to almost all environmental stresses, which is detrimental to the viability of the plant. Thus, controlling the production of stress ethylene in plants is emerging as an intriguing approach to boost crop production and mitigate the unwanted effects of abiotic stressors. Plants use 1-Aminocyclopropane-1-carboxylic acid (ACC) as a precursor to produce ethylene. It is well known that rhizobacteria that promote plant growth and have ACC deaminase activity can regulate plant growth in extreme conditions by lowering the levels of stress ethylene in plants. Researchers suggest that rhizobacteria that produce ACC deaminase can help plant development under varying environmental conditions, and bacteria with ACC deaminase could play a pivotal role in conferring tolerance and adaptation in plants to various abiotic stressors, indicating their great potential in addition to microbial plant biostimulants. In the present study, we aimed to describe the mechanism of ACC deaminase-producing rhizobacteria in plant growth promotion and tolerance to abiotic stress. [ABSTRACT FROM AUTHOR]

Main Conclusion: The consortium inoculation with strains R1 and R4 modified the root system to boost seedling growth, increase the zinc content of French bean pods, and reduce salinity stress. The present study demonstrated the effect of two 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing plant growth-promoting rhizobacteria (Pantoea agglomerans R1 and Pseudomonas fragi R4) alone and consortia on the root system development, French bean growth, and zinc content as well as salinity stress tolerance. Both the strains were characterized for ACC utilization activity (426.23 and 380.54 nmol α-ketobutyrate mg protein−1 h−1), indole acetic acid (IAA) production, phosphate solubilization, ammonia, hydrogen cyanide (HCN), and siderophore production. The strains exhibited zinc solubilization in both plate and broth assays with zinc oxide and zinc carbonate as zinc sources as validated by atomic absorption spectroscopy (AAS). Single or combined inoculations with the selected strains significantly modulated the architectural and morphological traits of the root system of French bean plants. Furthermore, the application of R1and R4 consortia has enhanced zinc content in roots (60.83 mg kg−1), shoots (15.41 mg kg−1), and pods (30.04 mg kg−1) of French bean plants grown in ZnCO3 amended soil. In another set of pot experiments, the consortium bacterization has significantly enhanced length as well as fresh and dry biomass of roots and shoots of the French bean plant under saline stress conditions. Additionally, inoculation with ACC-degrading rhizobacterial strains has increased chlorophyll and carotenoid contents, osmoprotectant content, and antioxidative enzyme (catalase and peroxidase) activity in comparison to their counterparts exposed to salt treatments only. Current findings suggested ACC deaminase-producing rhizobacterial strains hold the potential to improve root architecture which in turn promotes plant growth under salt-stressed conditions as well as enhances micronutrient concentration in host plants. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The elevation of the snowline of the No. 1 Glacier in the Tianshan Mountains is increasing due to global warming, which has created favorable conditions for moss invasion and offers an opportunity to investigate the synergistic effects of incipient succession by mosses, plants, and soils. In this study, the concept of altitude distance was used instead of succession time. To investigate the changes of bacterial-community diversity in moss-covered soils during glacial degeneration, the relationship between bacterial community structure and environmental factors was analyzed and valuable microorganisms in moss-covered soils were explored. To do so, the determination of soil physicochemical properties, high-throughput sequencing, the screening of ACC-deaminase-producing bacteria, and the determination of ACC-deaminase activity of strains were performed on five moss-covered soils at different elevations. The results showed that the soil total potassium content, soil available phosphorus content, soil available potassium content, and soil organic-matter content of the AY3550 sample belt were significantly different compared with those of other sample belts (p < 0.05). Secondly, there was a significant difference (p < 0.05) in the ACE index or Chao1 index between the moss-covered-soil AY3550 sample-belt and the AY3750 sample-belt bacterial communities as the succession progressed. The results of PCA analysis, RDA analysis, and cluster analysis at the genus level showed that the community structure of the AY3550 sample belt and the other four sample belts differed greatly and could be divided into two successional stages. The enzyme activities of the 33 ACC-deaminase-producing bacteria isolated and purified from moss-covered soil at different altitudes ranged from 0.067 to 4.7375 U/mg, with strains DY1–3, DY1–4, and EY2–5 having the highest enzyme activities. All three strains were identified as Pseudomonas by morphology, physiology, biochemistry, and molecular biology. This study provides a basis for the changes in moss-covered soil microhabitats during glacial degradation under the synergistic effects of moss, soil, and microbial communities, as well as a theoretical basis for the excavation of valuable microorganisms under glacial moss-covered soils. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Quorum sensing (QS) enables bacteria to organize gene expression programs, thereby coordinating collective behaviors. It involves the production, release, and population-wide detection of extracellular signaling molecules. The cellular processes regulated by QS in bacteria are diverse and may be used in mutualistic coordination or in response to changing environmental conditions. Here, we focused on the influence of the QS-dependent genes of our model bacterial strain Serratia fonticola GS2 on potential plant growth promoting (PGP) activities including indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and biofilm formation. Based on genomic and phenotypic experimental data we identified and investigated the function of QS genes in the genome of the model strain. Our gene deletion study confirmed the biological functionality of the QS auto-inducer (gloI) and receptor (gloR) on potential PGP activities of GS2. A transcriptomic approach was also undertaken to understand the role of QS genes in regulation of genes primarily involved in PGP activities (IAA, ACC deaminase activity, and biofilm formation). Both transcriptomic and phenotypic data revealed that the QS-deletion mutants had considerably less PGP activities, as compared to the wild type. In addition, in vivo plant experiments showed that plants treated with GS2 had significantly higher growth rates than plants treated with the QS-deletion mutants. Overall, our results showed how QS-dependent genes regulate the potential PGP activities of GS2. This information may be helpful in understanding the relationship between QS-dependent genes and the PGP activity of bacteria, which aid in the production of practical bio-fertilizers for plant growth promotion.

Abstract Plant growth-promoting endophytic (PGPE) actinomycetes have been known to enhance plant growth and mitigate plant from abiotic stresses via their PGP-traits. In this study, PGPE Streptomyces sp. GKU 895 promoted growth and alleviated salt tolerance of salt-susceptible rice cultivar IR29 by augmentation of plant weight and declined ROS after irrigation with 150 mM NaCl in a pot experiment. Transcriptome analysis of IR29 exposed to the combination of strain GKU 895 and salinity demonstrated up and downregulated differentially expressed genes (DEGs) classified by gene ontology and plant reactome. Streptomyces sp. GKU 895 induced changes in expression of rice genes including transcription factors under salt treatment which involved in growth and development, photosynthesis, plant hormones, ROS scavenging, ion transport and homeostasis, and plant–microbe interactions regarding pathogenesis- and symbiosis-related proteins. Taken together, these data demonstrate that PGPE Streptomyces sp. GKU 895 colonized and enhanced growth of rice IR29 and triggered salt tolerance phenotype. Our findings suggest that utilisation of beneficial endophytes in the saline fields could allow for the use of such marginal soils for growing rice and possibly other crops.

By decreasing root 1-aminocyclopropane-1-carboxylate (ACC) content and plant ethylene production, the microbial enzyme ACC deaminase is a widespread beneficial trait of plant growth-promoting rhizobacteria (PGPR), ameliorating ethylene-mediated root growth inhibition. However, relatively little is known about whether bacterial ACC deaminase modulates root architecture and root hair traits. Thus the dwarf tomato (Solanum lycopersicum) cultivar Micro-Tom was inoculated in vitro with Pseudomonas brassicacearum Am3, its ACC deaminase deficient mutant T8-1, a known PGPR strain Variovorax paradoxus 5C-2 or chemically treated with agents that promoted or inhibited ethylene production or sensitivity (Ag+, Co2+, and ACC). ACC treatment reduced both root elongation and the number of lateral roots, while ethylene inhibitors (Ag+, Co2+) and V. paradoxus 5C-2 promoted primary root elongation, but differentially affected lateral root length and number. Ag+ stimulated lateral root development, while Co2+ and V. paradoxus 5C-2 did not. Inoculation with P. brassicacearum Am3 and T8-1 inhibited elongation of the primary and lateral roots at a high inoculum concentration (106 cells cm3). All bacterial strains significantly increased the length and number of root hairs, with these effects more pronounced in P. brassicacearum Am3 than in the mutant T8-1. Treatment with Ag+ inhibited root hair formation and elongation, while Co2+ had the opposite effects. ACC treatment had no effect on root hair elongation but increased root hair density. While root growth inhibition caused by P. brassicacearum Am3 was independent of ACC deaminase, the promotion of root hair elongation and density by this strain was augmented by ACC deaminase activity. Thus ACC deaminase can modulate the morphological impacts of bacteria on root hair response by affecting plant ethylene content.

Growth and productivity of crop plants worldwide are often adversely affected by anthropogenic and natural stresses. Both biotic and abiotic stresses may impact future food security and sustainability; global climate change will only exacerbate the threat. Nearly all stresses induce ethylene production in plants, which is detrimental to their growth and survival when present at higher concentrations. Consequently, management of ethylene production in plants is becoming an attractive option for countering the stress hormone and its effect on crop yield and productivity. In plants, ACC (1-aminocyclopropane-1-carboxylate) serves as a precursor for ethylene production. Soil microorganisms and root-associated plant growth promoting rhizobacteria (PGPR) that possess ACC deaminase activity regulate growth and development of plants under harsh environmental conditions by limiting ethylene levels in plants; this enzyme is, therefore, often designated as a “stress modulator.” TheACC deaminase enzyme, encoded by the AcdS gene, is tightly controlled and regulated depending upon environmental conditions. Gene regulatory components of AcdS are made up of the LRP protein-coding regulatory gene and other regulatory components that are activated via distinct mechanisms under aerobic and anaerobic conditions. ACC deaminase-positive PGPR strains can intensively promote growth and development of crops being cultivated under abiotic stresses including salt stress, water deficit, waterlogging, temperature extremes, and presence of heavy metals, pesticides and other organic contaminants. Strategies for combating environmental stresses in plants, and improving growth by introducing the acdS gene into crop plants via bacteria, have been investigated. In the recent past, some rapid methods and cutting-edge technologies based on molecular biotechnology and omics approaches involving proteomics, transcriptomics, metagenomics, and next generation sequencing (NGS) have been proposed to reveal the variety and potential of ACC deaminase-producing PGPR that thrive under external stresses. Multiple stress-tolerant ACC deaminase-producing PGPR strains have demonstrated great promise in providing plant resistance/tolerance to various stressors and, therefore, it could be advantageous over other soil/plant microbiome that can flourish under stressed environments. [ABSTRACT FROM AUTHOR]

Biochar is considered one of the most promising long-term solutions for soil quality improvement, representing an ideal environment for microorganisms' immobilization. Hence there is a possibility to design microbial products formulated using biochar as a solid carrier. The present study was aimed at development and characterization of Bacillus-loaded biochar to be applied as a soil amendment. The producing microorganism Bacillus sp. BioSol021 was evaluated in terms of plant growth promotion traits, indicating significant potential for production of hydrolytic enzymes, indole acetic acid (IAA) and surfactin and positive tests for ammonia and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production. Soybean biochar was characterised in terms of physicochemical properties to evaluate its suitability for agricultural applications. The experimental plan for Bacillus sp. BioSol021 immobilisation to biochar included variation of biochar concentration in cultivation broth and adhesion time, while the soil amendment effectiveness was evaluated during maize germination. The best results in terms of maize seed germination and seedling growth promotion were achieved by applying 5% of biochar during the 48 h immobilisation procedure. Germination percentage, root and shoot length and seed vigour index were significantly improved when using Bacillus-biochar soil amendment compared to separate treatments including biochar and Bacillus sp. BioSol021 cultivation broth. The results indicated the synergistic effect of producing microorganism and biochar on maize seed germination and seedling growth promotion, pointing out the promising potential of this proposed multi-beneficial solution for application in agricultural practices. [ABSTRACT FROM AUTHOR]

Pogostemon cablin cultivation faces massive constraints because of its susceptability to drought stress that reduces patchouli propagation and oil yield. The present study has achieved an efficient and rapid direct regeneration system for the transgenic production of P. cablin using Agrobacterium-mediated genetic transformation. To establish an efficient regeneration protocol for fast in-vitro multiplication of patchouli plants, leaf, petiole, and transverse thin cell layer (tTCL) explants were used and inoculated on an MS medium supplemented with different combinations of phytohormones. A comparative study showed a maximum regeneration frequency of 93.30 ± 0.56% per explant was obtained from leaf segments on optimal MS medium fortified with 0.2mg/L BAP and 0.1mg/L NAA. Leaf and petiole explants took 25-35 days to regenerate while tTCL section showed regeneration in just 15-20 days on the same medium. Subsequently, productive genetic transformation protocol OD600 0.6, AS 200µM, 30mg/L kanamycin, and infection time 5 min. was standardized and best-suited explants were infected at optimum conditions from the Agrobacterium tumefaciens (LBA 4404) strain harboring ACC deaminase to generate transgenic P. cablin Benth. (CIM-Samarth) plants. The investigation suggested that the optimized protocol provides a maximum transformation frequency of 42 ± 1.9% in 15-20 days from tTCL. The transgenic plants were shifted to the greenhouse with a 52.0 ± 0.8% survival frequency. A molecular docking study confirmed significant binding affinity of ligand ACC with ACC deaminase at the catalytic site, and ligand interactions showed four H-bonds at the binding pocket with amino acids Cys-196, Val-198, Thr-199, and Gly-200 that validate gene relative expression in transgenic plants. Among all transgenic acclimatized greenhouse-grown patchouli plants, line PT4 showed improved drought resistance under severe water stress as its RWC was 71.7 ± 2.3% to 75.7 ± 2.1% which is greater than the RWC of the control plant, 58.30 ± 0.21%. Analysis of the other physiological indicators, H2O2, chlorophyll content, and ROS result support drought resistance ability. Our study concluded that the first report on P. cablin, tTCL direct regeneration, and standardized transformation protocol created a new opportunity for genetic manipulation to achieve drought-resistant patchouli plants for cultivation in all seasons at the commercial level.

Growth and productivity of crop plants worldwide are often adversely affected by anthropogenic and natural stresses. Both biotic and abiotic stresses may impact future food security and sustainability; global climate change will only exacerbate the threat. Nearly all stresses induce ethylene production in plants, which is detrimental to their growth and survival when present at higher concentrations. Consequently, management of ethylene production in plants is becoming an attractive option for countering the stress hormone and its effect on crop yield and productivity. In plants, ACC (1-aminocyclopropane-1-carboxylate) serves as a precursor for ethylene production. Soil microorganisms and root-associated plant growth promoting rhizobacteria (PGPR) that possess ACC deaminase activity regulate growth and development of plants under harsh environmental conditions by limiting ethylene levels in plants; this enzyme is, therefore, often designated as a “stress modulator.” TheACC deaminase enzyme, encoded by the AcdS gene, is tightly controlled and regulated depending upon environmental conditions. Gene regulatory components of AcdS are made up of the LRP protein-coding regulatory gene and other regulatory components that are activated via distinct mechanisms under aerobic and anaerobic conditions. ACC deaminase-positive PGPR strains can intensively promote growth and development of crops being cultivated under abiotic stresses including salt stress, water deficit, waterlogging, temperature extremes, and presence of heavy metals, pesticides and other organic contaminants. Strategies for combating environmental stresses in plants, and improving growth by introducing the acdS gene into crop plants via bacteria, have been investigated. In the recent past, some rapid methods and cutting-edge technologies based on molecular biotechnology and omics approaches involving proteomics, transcriptomics, metagenomics, and next generation sequencing (NGS) have been proposed to reveal the variety and potential of ACC deaminase-producing PGPR that thrive under external stresses. Multiple stress-tolerant ACC deaminase-producing PGPR strains have demonstrated great promise in providing plant resistance/tolerance to various stressors and, therefore, it could be advantageous over other soil/plant microbiome that can flourish under stressed environments.