Biochemistry and genetics of ACC deaminase: a weapon to “stress ethylene” produced in plants

Abstract

1-aminocyclopropane-1-carboxylate deaminase (ACCD), a pyridoxal phosphate-dependent enzyme, is widespread in diverse bacterial and fungal species. Owing to ACCD activity, certain plant associated bacteria help plant to grow under biotic and abiotic stresses by decreasing the level of “stress ethylene” which is inhibitory to plant growth. ACCD breaks down ACC, an immediate precursor of ethylene, to ammonia and α-ketobutyrate, which can be further metabolized by bacteria for their growth. ACC deaminase is an inducible enzyme whose synthesis is induced in the presence of its substrate ACC. This enzyme encoded by gene AcdS is under tight regulation and regulated differentially under different environmental conditions. Regulatory elements of gene AcdS are comprised of the regulatory gene encoding LRP protein and other regulatory elements which are activated differentially under aerobic and anaerobic conditions. The role of some additional regulatory genes such as AcdB or LysR may also be required for expression of AcdS. Phylogenetic analysis of AcdS has revealed that distribution of this gene among different bacteria might have resulted from vertical gene transfer with occasional horizontal gene transfer (HGT). Application of bacterial AcdS gene has been extended by developing transgenic plants with ACCD gene which showed increased tolerance to biotic and abiotic stresses in plants. Moreover, distribution of ACCD gene or its homolog's in a wide range of species belonging to all three domains indicate an alternative role of ACCD in the physiology of an organism. Therefore, this review is an attempt to explore current knowledge of bacterial ACC deaminase mediated physiological effects in plants, mode of enzyme action, genetics, distribution among different species, ecological role of ACCD and, future research avenues to develop transgenic plants expressing foreign AcdS gene to cope with biotic and abiotic stressors. Systemic identification of regulatory circuits would be highly valuable to express the gene under diverse environmental conditions.

Inoculation of Soil with Plant Growth Promoting Bacteria Producing 1-Aminocyclopropane-1-Carboxylate Deaminase or Expression of the Corresponding acdS Gene in Transgenic Plants Increases Salinity Tolerance in Camelina sativa

“…The effect of high stress ethylene levels in plants can be reduced by plant-associated bacteria that produce ACC deaminase, an enzyme that consumes the biochemical precursor for ethylene. This reduces stress ethylene and rescues normal plant growth while inducing systemic tolerance to stress in plants (Mayak et al, 2004; Glick et al, 2007; Yang et al, 2009; Lim and Kim, 2013; Singh et al, 2015). In the current study, we examined to the effect of inoculating soil with PGPB that produce ACC deaminase, as well as their corresponding acdS- mutants, on camelina salt tolerance.…”

“…However, some PGPB also produce the enzyme 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase). This enzyme converts the ethylene precursor ACC to α-ketobutyrate and ammonia and promotes plant growth, especially during stress conditions, by reducing the level of stress ethylene to below the point where it is inhibitory to growth (Glick, 1995, 2012; Singh et al, 2015). Salinity stress has been shown to elevate ethylene levels (Mayak et al, 2004), which affects almost all aspects of plant growth and development, including the response to biotic and abiotic stresses (Cao et al, 2008).…”

CONSTANS-Like 9 (OsCOL9) Interacts with Receptor for Activated C-Kinase 1(OsRACK1) to Regulate Blast Resistance through Salicylic Acid and Ethylene Signaling Pathways

“…Our results showed that the OsCOL9 expression could be significantly induced by exogenous addition of the ET precursor ACC. ACC synthase (ACS) and ACC oxidase (ACO) genes contribute to ET biosynthesis in blast fungus-infected rice plants [49], and the expression levels of these genes are increased. Compared with the wild-type plants, the expressions of OsACO1 and OsACO2 were significantly increased in OsCOL9-OX lines, while the expressions of OsACO7 and OsACS1 were decreased in oscol9-ko plants.…”

Isolation, identification, and detection of ACC deaminase gene-encoding rhizobacteria from rhizosphere of stressed pineapple

“…The BlastN search shown in Table 2 displays several strains and there is a pathogenic species, Bacillus anthracis (1E). Singh et al (2015) stated that ACC deaminase are widely found in human and plant pathogenic species, indicating that this enzyme plays an important role in microbial ecology. Furthermore, the distribution of this type of species in humans does not contribute to pathogenicity for some extent but rather the presence in diverse niche.…”

“…There are still less-understood regulatory mechanisms found in various genera of bacteria. The presence of this gene is very common in actinobacteria, Deinococcus-Thermus, proteobacteria and various fungi (Singh et al 2015). Recently, in Indonesia, the study of ACC deaminase-producing bacteria has begun to intensify, but its screening and molecular study continues to be very limited.…”