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The enzyme 1-aminocyclopropane-1-carboxylate deaminase catalyzes the degradation of 1-aminocyclopropane-1carboxylic acid (ACC), the immediate precursor of the plant hormone ethylene, into α-ketobutyrate and ammonia. The enzyme has been detected in a limited number of bacteria and plays a significant role in sustaining plant growth and development under biotic and abiotic stress conditions by reducing stressinduced ethylene production in plants. We have screened 32 fluorescent Pseudomonas sp. isolated from rhizosphere and non-rhizosphere soils of different crop production systems for drought tolerance using polyethylene glycol 6000 (PEG 6000). Nine of these isolates were tolerant to a substrate metric potential of −0.30 MPa (15 % PEG 6000) and therefore considered to be drought-tolerant. All of these drought-tolerant isolates were screened for ACC deaminase activity using ACC as the sole nitrogen source, and one (SorgP4) was found to be positive for ACC, producing 3.71±0.025 and 1.42±0.039 μM/mg protein/h of α-ketobutyrate under the non-stress and drought stress condition, respectively. The isolate SorgP4 also showed other plant growth-promoting traits, such as indole acetic acid production, phosphate solubilization, siderophore and hydrogen cyanide production. The ACC deaminase gene (acdS) from the isolate SorgP4 was amplified, and the nucleotide sequence alignment of the acdS gene showed significant homology with acdS genes of NCBI Genbank. The 16S rRNA gene sequencing analysis identified the isolate as Pseudomonas fluorescens. Both sequences have been submitted to the NCBI GenBank under the accession numbers JX885767 and KC192771 respectively.

The present study was carried out to investigate the effect of plant growth promoting thermotolerant Pseudomonas putida strain AKMP7 on the growth of wheat plants to heat stress. The results indicated the superior performance by P. putida strain AKMP7 in improving survival and growth of wheat plants under heat stress. The bacterium significantly increased the root and shoot length, dry biomass, tiller, spike let and grain formation of wheat over uninoculated plants. Inoculation reduced membrane injury and the activity of several antioxidant enzymes such as SOD, APX and CAT under heat stress. Inoculation improved the levels of cellular metabolites like proline, chlorophyll, sugars, starch, amino acids, and proteins compared to uninoculated plants. Scanning electron microscopy studies confirmed the colonization of the organism on the root surface. This result suggests the possible role of microorganisms in mitigating adverse effects of climate changes on crop growth and may lead to development of microbe based climate-ready technology.

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Plant growth-promoting rhizobacteria (PGPR) that produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase can alleviate plant growth constraints caused by water scarcity. In the present study, six PGPR strains were evaluated to produce several plant growth promoting, and ACC deaminase enzyme isolated from the rhizosphere soil of Chickpea (Cicer arietinum) in arid regions of Telangana State, India. According to their 16S rDNA sequencing analysis, only one of the six strains, MZ 3-ABF, belongs to Agrobacterium larrymoorie. A drought tolerance experiment revealed two PGPR strains with high phosphate solubilization, nitrogen fixation, indoleacetic-3-acid (IAA), and ACC deaminase enzyme secretion potential were constrained to only MZ 3-ABF and MZ 5-ABF. One strain MZ 3-ABF was chosen for use in a pot experiment to assess their growth-promoting effects on chickpea under drought conditions. This PGPR strain inoculation into chickpea seedlings was expected to alleviate the overall growth inhibition caused by drought stress. The inoculation was thought to have the greatest growth-promoting effects. Inoculation with strain MZ 3-ABF altered plant height, root length, dry biomass, and net photosynthetic rate of leaves, allowing chickpea seedlings to cope with drought better. They had an indirect effect on the biochemical and physiological properties of chickpea seedlings in order to alleviate drought stress. These findings suggest that the MZ 3-ABF PGPR may be useful for effectively weakening the growth inhibition caused by drought in chickpea. The strain could also be used as effective bioinoculant to maintain pea quality.