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Effectiveness of rhizobacteria containing ACC deaminase for growth promotion of peas (Pisum sativum) under drought conditions
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A series of experiments were conducted to assess the effectiveness of rhizobacteria containing 1-aminocyclopropane- 1-carboxylate (ACC) deaminase for growth promotion of peas under drought conditions. Ten rhizobacteria isolated from the rhizosphere of different crops (peas, wheat, and maize) were screened for their growth promoting ability in peas under axenic condition. Three rhizobacterial isolates, Pseudomonas fluorescens biotype G (ACC-5), P. fluorescens (ACC-14), and P. putida biotype A (Q-7), were selected for pot trial on the basis of their source, ACC deaminase activity, root colonization, and growth promoting activity under axenic conditions. Inoculated and uninoculated (control) seeds of pea cultivar 2000 were sown in pots (4 seeds/pot) at different soil moisture levels (25, 50, 75, and 100% of field capacity). Results revealed that decreasing the soil moisture levels from 100 to 25% of field capacity significantly decreased the growth of peas. However, inoculation of peas with rhizobacteria containing ACC deaminase significantly decreased the "drought stress imposed effects" on growth of peas, although with variable efficacy at different moisture levels. At the lowest soil moisture level (25% field capacity), rhizobacterial isolate Pseudomonas fluorescens biotype G (ACC-5) was found to be more promising compared with the other isolates, as it caused maximum increases in fresh weight, dry weight, root length, shoot length, number of leaves per plant, and water use efficiency on fresh and dry weight basis (45, 150, 92, 45, 140, 46, and 147%, respectively) compared with respective uninoculated controls. It is highly likely that rhizobacteria containing ACC deaminase might have decreased the drought-stress induced ethylene in inoculated plants, which resulted in better growth of plants even at low moisture levels. Therefore, inoculation with rhizobacteria containing ACC deaminase could be helpful in eliminating the inhibitory effects of drought stress on the growth of peas.
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... It has been reported that some rhizobacterial strains contribute positively to plant growth under drought stress conditions (Taha et al. 2022;Dadashi et al. 2023;Waqar et al. 2022;Azeem et al. 2022;Fonseca et al. 2022). PGPRs, in particular, secrete 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and reduce the levels of ACC, the precursor of ethylene in plants, which increases plant resistance to water stress (Zahir et al. 2008). Several studies have shown that the rhizobacteria that synthesize ACC deaminase effectively protect plants from many abiotic stress factors, including drought (Sarma and Saikia 2014;Zafar-ul-Hye et al. 2019;Mayak et al. 2004;Kausar and Shahzad 2006;Yavuz et al. 2023;Nadeem et al. 2007). ...
Currently, many techniques to alleviate the negative effects of water stress, specifically drought, on plants are frequently the subject of research. In this study, the effects of two different plant growth-promoting rhizobacterial (PGPR) species isolated from arid and semiarid areas whose activities under water stress were determined in a preliminary study on several physiological properties and nutrient uptake of watermelons grafted onto different rootstocks were investigated under deficit irrigation. In this study, the performance of two PGPRs (B1: Paenarthrobacter aurescens and B2: Pseudarthrobacter polychromogenes) inoculated into ungrafted watermelon (R0 (Citrullus lanatus (Thumb.) Matsum and Nakai cv. Crimson Tide, CT)) and grafted watermelons (R1: CT grafted onto citron watermelon rootstock (Citrullus lanatus var. Citroides) and R2: CT grafted onto the hybrid rootstock TZ-148 (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne)) were studied under different irrigation levels. Severe water stress negatively affected the physiological characteristics, such as stomatal conductance (gs) and photosynthesis efficiency (QPSII), of watermelon plants. Moreover, the contents of leaf mineral nutrients such as N, P, and K decreased significantly with increasing water stress. On the other hand, rootstocks improved the performance of sweet watermelon in terms of macronutrients such as N, K, and Mg and micronutrients such as Fe and Cu. Moreover, the drought-tolerant rootstocks (R1 and R2) used in this study protected watermelon plants against the negative effects of water stress by reducing gs compared to that of ungrafted plants. Moreover, although rhizobacteria did not have a significant effect on the gs, QPSII, or leaf water potential (LWP) of watermelon, they enhanced the uptake of minerals such as macro- and micronutrients from the soil by plants. Under full irrigation and particularly deficit irrigation, P. polychromogenes (B2) increased the contents of macronutrients such as Mg and K, while P. aurescens (B1) increased the contents of micronutrients such as Fe, Cu, Mn, and B in watermelons. Our results revealed that these two rhizobacterial species, which were isolated from arid and semiarid areas, contribute to the nutrient uptake of watermelon plants grown under water stress.
... These phytohormone, which is produced by rhizobacteria, is crucial for promoting plant development. PGPR has the capacity to lessen the harmful effects of ethylene generated under various stressors, containing DS (Zahir, Munir, Asghar, Shaharoona, & Arshad, 2008) and waterlogging (Grichko & Glick, 2001). Earlier studies showed that PGPR regulates various stressors through ABA regulation and together boost the plants' efficacy during stress conditions (Herrera-Medina, Steinkellner, Vierheilig, Bote, & Garrido, 2007). ...
... Using PGPB that contains ACC deaminase can help prevent high amounts of ethylene and the harm it causes, as was previously discussed when talking about the stress ethylene produced as a result of phytopathogen infection [142]. Extremes in temperature [143], floods [144], drought [145,146], metals and metaloids [60,61,[147][148][149][150][151][152], hypoxia [153], salt [154][155][156][157][158][159][160][161][162][163][164][165], and organic pollutants [150,151,[166][167][168] are a few abiotic stressors whose impacts can be lessened in this way. According to the aforementioned reports from around the globe, a variety of ACC deaminasecontaining PGPB can significantly protect plants from a variety of abiotic stresses. ...
The ability of agricultural systems to provide food globally may be limited by growing environmental concerns. The biggest issue the world is now dealing with is climate change. By 2050, food production will need to quadruple to fulfill the world's food demand. In the field of sustainable agriculture, plant growth-promoting bacteria (PGPB) have been shown to have a significant impact. Increasing agricultural yield while using less synthetic chemical fertilizers and pesticides is a major issue in today's world. It has been demonstrated that using PGPB to promote plant development through direct or indirect means is a sustainable method of raising agricultural yields. Among PGPB's processes are the control of hormonal and nutritional balance, the development of resistance against plant diseases, and the solubilization of minerals to facilitate their simple absorption by plants. Moreover, PGPB interact both antagonistically and synergistically with microorganisms in bulk soil and the rhizosphere, which indirectly accelerates plant development. Numerous bacterial species have been reported in the literature to function as PGPR and to effectively enhance plant development. There is a difference, nevertheless, between the PGPR's function as a biofertilizer and its method of action (mechanism) for plant development. Therefore, this analysis fills in the aforementioned void and provides an overview of PGPR's mechanism as a biofertilizer for sustainable agriculture.
... Increases in fresh plant weight by the utilization of native PGPRs were also recorded by Prashant et al. (2009) in wheat plants. Zahir et al. (2008) also reported that inoculation with Pseudomonas fluorescens increased in root and shoot length, number of leaves per plant of pea plants and fresh and dry weight. Similar findings were also recorded by Samy et al. (2007) who reported that inoculation with Pseudomonas aeruginosa increased the number of pods per plant, shoot dry weight and nodule dry weight of faba bean. ...
The intensive agricultural system results into considerable environmental damage and its inevitable effects on various environmental and ecological factors. Known for their role in the natural disease-suppressiveness of particular soil, Fluorescent pseudomonads are a genus of root-associated bacteria that may colonise the roots of agricultural plants and create antifungal metabolites, making them a viable alternative to the use of chemical fungicides. The successful application of Fluorescent pseudomonads as bioinoculants depends to a great extent on their capability to establish roots and to contend with indigenous microbiome in the rhizosphere. Because of various limitations, variations in the bio control agents are bound to occur in different agro-climatic regions, so it is advisable to choose native bio control agents. In the present investigation, a comprehensive effort was undertaken to check the growth of Pseudomonas aeruginosa (GP-8), which was found to be much lesser in aqueous extracts of cow dung, vermicompost and groundnut cake as compared to the growth of GP-8 (Pseudomonas aeruginosa) in nutrient broth media. The enrichment of Nitrogen and other supplementary nutrients may be required for the development of low cost indigenous media from cheaply available substrates for commercial mass production of Pseudomonas aeruginosa (GP-8) and also a field level screening trial was undertaken with efficient native Fluorescent pseudomonads solely or in consortia for improvement of plant health and management of soil borne pathogens as well as to develop a culture media with cheap and readily available substrate sources for mass production of Fluorescent pseudomonads strains. In the present study, it was found that shoot length and root length of native Fluorescent pseudomonads inoculated cowpea plants were significantly increased as compared with those of the control plants both at 30 and 60 days after sowing.
... Exopolysaccharides producing bacteria greatly contribute in plant growth promotion and drought tolerance through a variety of ways, and beneficial effects of their inoculation on field crops have been demonstrated in several studies [16]. Inoculation with P. fluorescens and P. putida increased fresh weight of plants [56]. Compatibility of biostimulants to maize in terms of ear weight and grain count through inoculation with Klebsiella MK2R2 and Bacillus B2L2 alone as well as combined with Enterobacter E1S2 has been reported [57]. ...
Land productivity in arid and hot climate regions is constrained by water scarcity due to low rainfall and organic matter, which limit both soil-water retention and crop yields. Main objective of this research was to explore the potential of exopolysaccharide (EPS) producing bacteria screened from different soils for enhancing soil-water retention, phosphorus solubilization and maize growth. Twelve soil samples were drawn from diverse ecologies (sub-humid and arid) to isolate EPS-producing bacteria (EPB), and cultured on LB and Pikovskaya media. Nine bacterial strains were found to have EPS production characteristic; among from them, 2 most efficient EPB strains were selected and characterized through morphological, biochemical and molecular standard procedures of bacterial identification. These potent EPB-strains were characterized as Pseudomonas aeruginosa EPB9 and Bacillus cereus EPB17. Broth cultures of 2 and 10 days old (2d and 10d) both EPB strains were used as soil inoculant to grow maize in growth chamber under triplicated factorial CRD. Treatments were: Control, LB broth (without inoculum), EPB9-2d, EPB9-10d, EPB17-2d, and EPB17-10d inoculation in both non-stressed and drought-stressed soils. Experiment lasted for 24 days, when soil and plant leaf water contents, plant growth attributes and antioxidant enzymes were measured. Inoculation of both EPB strains significantly enhanced maize growth and soil-water retained until harvesting stage. Higher water contents in soil and plant leaves, as well as fresh shoot and root weight were with EPB9-10d. Plant leaf area and shoot length were greater with EPB17-10d inoculation. Bacterial EPS also caused higher protein and sugar, and lower proline contents in plants. Antioxidant enzymes (SOD, POD and CAT) remained lower with both EPB treatments due to reduced drought stress than in control. It was evident that efficient EPB strains could survive even under osmotic stress, and retain more soil-water for longer time. Further, antioxidant enzymes and EPS interact together for drought tolerance and growth promotion of plants. Therefore, study concludes that under limited water conditions, soil
The microbiome has emerged as a significant factor in understanding plant adaptation, impacting overall plant health and resilience. This chapter notably examines the potential role of environmentally friendly plant growth-promoting rhizobacteria (PGPR) in enhancing crop yields and mitigating stress-related challenges. It explores the complex dynamics that govern interactions between plants and microorganisms, emphasizing their crucial roles in promoting plant growth and enhancing stress tolerance, particularly in challenging environmental conditions. Specifically, this study investigates the complex metabolic processes of rhizobacteria, with a particular emphasis on the crucial roles of polyamines and proline as effective compounds produced by rhizobacteria. These compounds stimulate plant growth and improve stress responses. Furthermore, it explores the capacity of PGPR to produce phytohormones, such as indole-3-acetic acid (IAA), and to synthesize exopolysaccharides to enhance plant growth. This study highlights the catalytic function of ACC deaminase in influencing plant growth and enhancing stress resistance. ACC deaminase plays a crucial role in enhancing plant resilience against abiotic stress in various plant species. This chapter offers valuable insights into the network of interactions between plants and microbes, providing potential solutions for enhancing crop performance under challenging stress conditions and promoting sustainable agricultural practices.
The mutualistic plant rhizobacteria which improve plant development and productivity are known as plant growth-promoting rhizobacteria (PGPR). It is more significant due to their ability to help the plants in different ways. The main physiological responses, such as malondialdehyde, membrane stability index, relative leaf water content, photosynthetic leaf gas exchange, chlorophyll fluorescence efficiency of photosystem-II, and photosynthetic pigments are observed in plants during unfavorable environmental conditions. Plant rhizobacteria are one of the more crucial chemical messengers that mediate plant development in response to stressed conditions. The interaction of plant rhizobacteria with essential plant nutrition can enhance the agricultural sustainability of various plant genotypes or cultivars. Rhizobacterial inoculated plants induce biochemical variations resulting in increased stress resistance efficiency, defined as induced systemic resistance. Omic strategies revealed plant rhizobacteria inoculation caused the upregulation of stress-responsive genes—numerous recent approaches have been developed to protect plants from unfavorable environmental threats. The plant microbes and compounds they secrete constitute valuable biostimulants and play significant roles in regulating plant stress mechanisms. The present review summarized the recent developments in the functional characteristics and action mechanisms of plant rhizobacteria in sustaining the development and production of plants under unfavorable environmental conditions, with special attention on plant rhizobacteria-mediated physiological and molecular responses associated with stress-induced responses.
Rhizobacteria were isolated from the rhizosphere of different Brassica species and assayed for their ability to produce auxins in vitro. The isolates varied greatly in their potential for auxin production (ranging from 0.33 to 11.40 g ml-1). L-Tryptophan (an auxin precursor) addition to the media increased the auxin production by several fold. Based upon in vitro auxin production and growth promotion of B. juncea seedlings caused by various isolates under gnotobiotic conditions, promising isolates were selected and tested in pot trial to observe their effects on growth, yield and oil content of the same Brassica species. Results showed that seed inoculation with different isolates of rhizobacteria significantly increased plant height (up to 56.5%), stem diameter (up to 11.0%), number of branches (up to 35.7%), number of pods per plant (up to 26.7%), 1,000-grain weight (up to 33.9%), grain yield (up to 45.4%) and oil content (up to 5.6%) over the uninoculated control. Isolate S54 gave the most promising and consistent results. Highly significant correlations between L-TRP-derived auxin production by plant growth-promoting rhizobacteria (PGPR) in vitro and grain yield (r =0.77**), number of pods (r =0.78**) and number of branches per plant (r =0.77**) of B. juncea were found. It was hypothesized that these PGPR may influence the growth and yield of inoculated plants by production of auxins in the rhizosphere of inoculated plants from the L-TRP present in the root exudates, although other mechanisms of action might have also contributed.
Seeds of wild-type tomato plants Lycopersicon esculentum (Solanaceae) cv. Heinz 902 were inoculated either with Enterobacter cloacae UW4, E. cloacae CAL2, Pseudomonas putida ATCC17399/pRKACC or P. putida ATCC17399/pRK415, the first three of these bacterial strains carrying and expressing the gene for 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. When they were 55 d old, tomato plants were flooded for nine consecutive days before a number of physiological and biochemical parameters were assessed. Characteristics that were observed include root and shoot growth, epinastic curvature in leaf petioles, ACC deaminase activity, ethylene production, and leaf chlorophyll concentration. Tomato plants that were grown from seeds bacterized with organisms expressing ACC deaminase showed a substantial tolerance to flooding stress.
The work reported here evaluates whether bacteria populating arid and salty environments can confer resistance in tomato and pepper plants to water stress. Plant growth-promoting bacteria that have ACC deaminase activity were isolated from soil samples taken from the Arava region of southern Israel. One of these strains, Achromobacter piechaudii ARV8 [Mayak et al., Plant growth-promoting bacteria that confer resistance in tomato and pepper plants to salt stress, submitted for publication.] significantly increased the fresh and dry weights of both tomato and pepper seedlings exposed to transient water stress. In addition, the bacterium reduced the production of ethylene by tomato seedlings, following water stress. During water deprivation the bacterium did not influence the reduction in relative water content; however, it significantly improved the recovery of plants when watering was resumed. Inoculation of tomato plants with the bacterium resulted in continued plant growth during both the water stress and after watering was resumed. Based on the results of the experiments reported herein, the use of plant growth-promoting bacteria such as A. piechaudii ARV8 may provide a means of facilitating plant growth in arid environments.
A plant growth-promoting bacterium, Kluyvera ascorbata SUD165, that contained high levels of heavy metals was isolated from soil collected near Sudbury, Ontario, Canada. The bacterium was resistant to the toxic effects of Ni2+, Pb2+, Zn2+, and CrO4−, produced a siderophore(s), and displayed 1-aminocyclopropane-1-carboxylic acid deaminase activity. Canola seeds inoculated with this bacterium and then grown under gnotobiotic conditions in the presence of high concentrations of nickel chloride were partially protected against nickel toxicity. In addition, protection by the bacterium against nickel toxicity was evident in pot experiments with canola and tomato seeds. The presence of K. ascorbata SUD165 had no measurable influence on the amount of nickel accumulated per milligram (dry weight) of either roots or shoots of canola plants. Therefore, the bacterial plant growth-promoting effect in the presence of nickel was probably not attributable to the reduction of nickel uptake by seedlings. Rather, it may reflect the ability of the bacterium to lower the level of stress ethylene induced by the nickel.
It was previously shown that a number of plant growth promoting rhizobacteria contain an enzyme, 1-aminocyclopropane-1-carboxylate deaminase, that catalyses the cleavage of 1-aminocyclopropane-1-carboxylate, the immediate precursor of ethylene in plants. Moreover, experimental evidence indicated that the activity of this enzyme was the key factor in the ability of plant growth promoting rhizobacteria to stimulate the elongation of plant roots. In the model presented in this manuscript we address the question of how the bacterial enzyme 1-aminocyclopropane-1-carboxylate deaminase, with a low affinity for 1-aminocyclopropane-1-carboxylate, can effectively compete with the plant enzyme 1-aminocyclopropane-1-carboxylate oxidase, which has a high affinity for the same substrate, 1-aminocyclopropane-1-carboxylate, with the result that the plant's endogenous ethylene concentration is reduced. It is argued that the simplest explanation for the observed biological activity of plant growth promoting rhizobacteria relates to the relative amounts of 1-aminocyclopropane-1-carboxylate deaminase and 1-aminocyclopropane-1-carboxylate oxidase in the system under consideration. For plant growth promoting rhizobacteria to be able to lower plant ethylene levels, the 1-aminocyclopropane-1-carboxylate deaminase level should be at least 100- to 1000-fold greater then the 1-aminocyclopropane-1-carboxylate oxidase level. This is likely to be the case, provided that the expression of 1-aminocyclopropane-1-carboxylate oxidase has not been induced.Copyright 1998 Academic Press Limited Copyright 1998 Academic Press Limited
Several microorganisms capable of utilizing 1-aminocyclopropane-l-carboxylate (ACPC) were isolated from soil. A bacterium which belongs to Pseudomonas accumulated cellular a-aminobutyrate with consumption of ACPC and cells incubated with ACPC medium had the activity deaminating the substrate to form α-ketobutyrate. An enzyme, ACPC deaminase, was highly purified and its molecular weight, substrate specificity and absorption spectrum were investigated. These results suggested that this enzyme was a pyridoxal 5'-phosphate enzyme which has the molecular weight of 104000 and high specificity for ACPC, Km=1.5mM. A yeast, Hansenula saturnus, is also capable of forming ACPC deaminase, which has a lower molecular weight, 69000, and higher Km value, 2.6mM.
Excised wheat (Triticum aestivum L.) leaves, when subjected to drought stress, increased ethylene production as a result of an increased synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC) and an increased activity of the ethyleneforming enzyme (EFE), which catalyzes the conversion of ACC to ethylene. The rise in EFE activity was maximal within 2 h after the stress period, while rehydration to relieve water stress reduced EFE activity within 3 h to levels similar to those in nonstressed tissue. Pretreatment of the leaves with benzyladenine or indole-3-acetic acid prior to water stress caused further increase in ethylene production and in endogenous ACC level. Conversely, pretreatment of wheat leaves with abscisic acid reduced ethylene production to levels produced by nonstressed leaves; this reduction in ethylene production was accompanied by a decrease in ACC content. However, none of these hormone pretreatments significantly affected the EFE level in stressed or nonstressed leaves. These data indicate that the plant hormones participate in regulation of water-stress ethylene production primarily by modulating the level of ACC.
When plants are subject to a variety of stresses they often exhibit symptoms of exposure to ethylene. Although this relationship usually results from induction of ACC synthase thus raising the concentration of the precursor of ethylene, it is now apparent that there are numerous other ways that stresses produce ethylene-like symptoms. This complex relationship between stress and ethylene-like symptoms is here termed the stress ethylene syndrome. ACC synthase exists as a multi-gene family whose individual members are differentially regulated, many by various stresses. In addition, ACC oxidase. AdoMet synthetase, enzymes in the Yang methionine cycle, and enzymes that conjugate ACC are regulated by stress. In more unusual cases, ethylene production is not increased by stress or may be reduced. There is evidence for stress effects on perception of ethylene and the potential exists that some steps of the ethylene signal transduction pathway may be influenced by stress. Because of the variability possible in the stress ethylene syndrome, it continues to be studied for a number of stresses and species. In particular, attention is being given to wounding, mechanical stress, drought, heat and water deficit stress, chilling, air pollution, chemical and salt stress, and low O2stress. It is becoming more apparent that a number of stress responses involve interactions with other hormones.
Some plant-growth-promoting rhizobacteria (PGPR) promote plant growth by lowering the endogenous ethylene synthesis in the roots through their 1-aminocylopropane-1-carboxylate (ACC)-deaminase activity. However, in the vicinity of the roots may decrease the efficiency of these PGPR by stimulating ACC-oxidase activity resulting in greater ethylene production by the roots. This study was designed to assess the performance of PGPR containing ACC-deaminase for improving growth and yield of maize grown in N-amended soil. Several strains of rhizobacteria containing ACC-deaminase were screened for their growth-promoting activity in maize roots under gnotobiotic conditions. Six strains were selected and their effectiveness in soil amended with N at a concentration of 175 kg ha−1 (1050 mg pot−1) was investigated by conducting a pot trial on maize. Significant increases in plant height, root weight and total biomass were observed in response to inoculation. Based upon the results of pot trials, the three most efficient strains were selected and tested in the field for their effectiveness in the presence and absence of N fertilizer. Results of the field trial revealed that the inoculum performed relatively better in the absence of N-fertilizer application. Pseudomonas fluorescens biotype G (N3) was the most effective strain both in the presence and absence of N fertilizer. Results may imply that even in the presence of optimum levels of nitrogenous fertilizers, inoculation with rhizobacteria containing ACC-deaminase activity could be effective to improve the growth and yield of inoculated plants.