Pseudomonas 1-aminocyclopropane-1-carboxylate (ACC) Deaminase and Its Role in Beneficial Plant-Microbe Interactions

The expression of the enzyme 1-aminocylopropane-1-carboxylate (ACC) deaminase, and the consequent modulation of plant ACC and ethylene concentrations, is one of the most important features of plant-associated bacteria. By decreasing plant ACC and ethylene concentrations, ACC deaminase-producing bacteria can overcome some of the deleterious effects of inhibitory levels of ACC and ethylene in various aspects of plant-microbe interactions, as well as plant growth and development (especially under stressful conditions). As a result, the acdS gene, encoding ACC deaminase, is often prevalent and positively selected in the microbiome of plants. Several members of the genus Pseudomonas are widely prevalent in the microbiome of plants worldwide. Due to its adaptation to a plant-associated lifestyle many Pseudomonas strains are of great interest for the development of novel sustainable agricultural and biotechnological solutions, especially those presenting ACC deaminase activity. This manuscript discusses several aspects of ACC deaminase and its role in the increased plant growth promotion, plant protection against abiotic and biotic stress and promotion of the rhizobial nodulation process by Pseudomonas. Knowledge regarding the properties and actions of ACC deaminase-producing Pseudomonas is key for a better understanding of plant-microbe interactions and the selection of highly effective strains for various applications in agriculture and biotechnology.

Study of the ascorbate-glutathione cycle in transgenic plants Nicotiana tabacum under abiotic stress conditions

We conducted a comparative analysis of biochemical parameters for the ascorbate-glutathione cycle in non-transgenic and transgenic Nicotiana tabacum, plants cultivated in heavy metal polluted soils. Transgenic plants had in their genome a bacterial acdS-gene encoding the 1-aminocyclopropane-1-carboxylate deaminase (ACC-deaminase) enzyme. The introduction of elevated concentrations of copper, chromium, and lead ions into the soil promotes induction of the acdS-gene expression and an increase in ACC-deaminase activity in transgenic plants. It was shown the content of ascorbic acid (АА), glutathione, ascorbate peroxidase (АРХ) and glutathione peroxidase (GP) and glutathione reductase (GR) increased in plants under abiotic stress.

Evaluation of Indigenous Olive Biocontrol Rhizobacteria as Protectants against Drought and Salt Stress

Stress caused by drought and salinity may compromise growth and productivity of olive (Olea europaea L.) tree crops. Several studies have reported the use of beneficial rhizobacteria to alleviate symptoms produced by these stresses, which is attributed in some cases to the activity of 1-aminocyclopropane-1-carboxylic acid deaminase (ACD). A collection of beneficial olive rhizobacteria was in vitro screened for ACD activity. Pseudomonas sp. PICF6 displayed this phenotype and sequencing of its genome confirmed the presence of an acdS gene. In contrast, the well-known root endophyte and biocontrol agent Pseudomonas simiae PICF7 was defective in ACD activity, even though the presence of an ACD-coding gene was earlier predicted in its genome. In this study, an unidentified deaminase was confirmed instead. Greenhouse experiments with olive ‘Picual’ plants inoculated either with PICF6 or PICF7, or co-inoculated with both strains, and subjected to drought or salt stress were carried out. Several physiological and biochemical parameters increased in stressed plants (i.e., stomatal conductance and flavonoids content), regardless of whether or not they were previously bacterized. Results showed that neither PICF6 (ACD positive) nor PICF7 (ACD negative) lessened the negative effects caused by the abiotic stresses tested, at least under our experimental conditions.

The influence of bacteria acdS-gene of Pseudomonas putida B-37 on Nicotiana tabacum transgenic plants under abiotic stress conditions

In the present work was carried out selection of transgenic plants of Nicotiana tabacum carrying acdS-gene of bacteria Pseudomonas putida B-37. Using polymerase chain reaction with specific primers, the presence of the target gene was proved. Transgenic plants selected on a selective medium were planted in the ground and subjected to abiotic stress caused by soil contamination with heavy metal salts (15 mg / kg for Cu2+ and 30 mg / kg for Cr6+ and Pb2+ ) and salinization of the soil (200 mmol/L NaCl). Reverse transcription polymerase chain reaction and real-time polymerase chain reaction were conducted and confirmed the transcriptional activity of the bacterial acdS-gene in transgenic plant cells at a level with the reference gene Ef-1a. Determination of activity of ACC-deaminase, the product of expression of the acdS-gene, confirmed the formation of the active enzyme in the leaf tissues of transgenic tobacco plants. The beneficial effect of the acdS-gene of the bacteria P. putida B-37 on transgenic N. tabacum plants under abiotic stress has been proven.

Analysis of the low-molecular weight antioxidants of transgenic plants Nicotiana tabacum under abiotic stress conditions

We conducted a comparative analysis of biochemical parameters of non-transgenic and transgenic Nicotiana tabacum, plants cultivated in heavy metal polluted soils. Transgenic plants had in their genome a bacterial acdS-gene encoding the 1-aminocyclopropane-1-carboxylate deaminase (ACC-deaminase) enzyme. The introduction of elevated concentrations of copper, chromium, and lead ions into the soil promotes induction of the acdS-gene expression and an increase in ACC-deaminase activity in transgenic plants. It was shown that the content of phenolic compounds (flavonoids), ascorbic acid, the total antioxidant activity of plants increased under abiotic stress.

Enhancing the 1-Aminocyclopropane-1-Carboxylate Metabolic Rate of Pseudomonas sp. UW4 Intensifies Chemotactic Rhizocompetence

1-aminocyclopropane-1-carboxylic acid (ACC) is a strong metabolism-dependent chemoattractant for the plant beneficial rhizobacterium Pseudomonas sp. UW4. It is unknown whether enhancing the metabolic rate of ACC can intensify the chemotaxis activity towards ACC and rhizocompetence. In this study, we selected four promoters to transcribe the UW4 ACC deaminase (AcdS) gene in the UW4 ΔAcdS mutant. PA is the UW4 AcdS gene promoter, PB20, PB10 and PB1 are synthetic promoters. The order of the AcdS gene expression level and AcdS activity of the four strains harboring the promoters were PB20 > PA > PB10 > PB1. Interestingly, the AcdS activity of the four strains and their parent strain UW4 was significantly positively correlated with their chemotactic activity towards ACC, rhizosphere colonization, roots elongation and dry weight promotion. The results released that enhancing the AcdS activity of PGPRenable them to achieve strong chemotactic responses to ACC, rhizocompetence and plant growth promotion.

Expression analysis of acdS-gene of Pseudomonas putida B-37 in transgenic plants Nicotiana tabacum

In current work was realized the transfer of recombinant plasmid pBI121acdS, carring P. putida B-37 bacterial acdSgene to the A. tumefaciens AGL0 cells. Transgenic plants of N. tabacum were created by agrobacterial transformation. Integration of P. putida B-37 bacterial acdS-gene to transgenic plants of N. tabacum was verified by PCR analysis, using specific primers to present gene. Presence of target acdS-gene in transgenic plants genome was proved by RT-PCR analysis. With help of Real-time PCR was shown the difference between reference gene and target P. putida B-37 bacterial acdSgene expression. Expression of target gene exceeded reference gene in 1.27 times, those fact proved expression of acdS-gene in plants on high level. Expression of the heterologous gene in N. tabacum plants was also proved by biochemical method of ACC-deaminase specific activity define.