Browsing by Author "Ashutosh K. Rai"

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Down-regulation of the alternative sigma factor SIGJ confers a photoprotective phenotype to anabaena PCC 7120
(Oxford University Press, 2017) Amit Srivastava; Klaus Brilisauer; Ashutosh K. Rai; Anand Ballal; Karl Forchhammer; Anil K. Tripathi
Alternative sigma factors belonging to Group 3 are thought to play an important role in the adaptation of cyanobacteria to environmental challenges by altering expression of genes needed for coping with such stresses. In this study, the role of an alternative sigma factor, SigJ, was analyzed in the filamentous nitrogen-fixing cyanobacterium, Anabaena sp. PCC 7120 by knocking down the expression of the sigJ gene (alr0277) employing an antisense RNA-mediated approach. In the absence of any stress, the knock-down (KD0277) or the wild-type strain both grew similarly. Upon exposure to high-intensity light, KD0277 showed substantially reduced bleaching of its pigments, higher photosynthetic activity and consequently better survival than the wild type. KD0277 also showed an enhanced accumulation of two carotenoids, which were identified as myxoxanthophyll and keto-myxoxanthophyll. Further, KD0277 was more tolerant to ammonium- triggered photodamage than the wild type. Moreover, PSII was better protected against photodamage in KD0277 than in the wild type. Down-regulation of sigJ in Anabaena PCC 7120, however, reduced its ability to cope with desiccation. This study demonstrates that down-regulation of the sigJ gene in Anabaena PCC 7120 differentially affects its ability to tolerate two environmentally relevant stresses, i.e. high-intensity light and desiccation. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists..
Rhizosphere of rice plants harbor bacteria with multiple plant growth promoting features
(Academic Journals, 2011) Shailesh K. Shahi; Ashutosh K. Rai; Madhu B. Tyagi; Rajeshwar P. Sinha; Ashok Kumar
114 diazotrophic bacteria from the rice rhizosphere of five districts of Eastern Uttar Pradesh (India) were isolated and screened for plant growth promoting (PGP) activities employing standard microbiological and biochemical techniques. All these isolates showed nitrogenase activity in the range of 0.23 to 1.72 μmol C2H4 mg-1protein h-1. Further analysis showed that 84 (73.68%) isolates were Indole-3-acetic acid (IAA) producer; the value of IAA production ranged from 10.1 to 353.0 μg IAA mg-1 protein. IAA production occurred solely in the medium supplemented with tryptophan. P solubilization activity was observed in 28 (24.56%) isolates, the activity being in the range of 38.50 to 321.0 P released μg mg-1 protein. 45 (39.46%) isolates were capable of producing siderophore, the range of production being 4.50 to 223.26 μg mg-1 protein. Analysis of molecular diversity was made by amplified ribosomal DNA restriction analysis (ARDRA) and denaturating gradient gel electrophoresis (DGGE), which exhibited distinct differences among all the isolates. Of the 114 isolates, twenty one (21) isolates showed multiple plant growth promoting traits and were potent in terms of PGP activities. These isolates were identified on the basis of 16S rDNA sequencing and belonged to the genera Pantoea, Bacillus, Microbacterium, Pseudomonas, Sphingomonas, Ancylobacter, Enterobacter, Advenella, γ-proteobacterium strain VA3S1, Rhizobium and Agrobacterium. Findings of this study suggest that certain isolates may be exploited for developing a potential source of biofertilizer. © 2011 Academic Journals.