Nitrogen status and heat-stress-dependent differential expression of the cpn60 chaperonin gene influences thermotolerance in the cyanobacterium Anabaena

Rajaram, Hema; Apte, Shree Kumar

doi:10.1099/mic.0.2007/011064-0

Cited by 41 publications

(24 citation statements)

References 29 publications

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“…Inactivation of the photosystems upon temperature upshift has been shown both in the unicellular cyanobacteria Synechocystis PCC6803 (Glatz et al, 1999;Mamedov et al, 1993) and Synechococcus PCC7942 (Eriksson & Clarke, 1996) and in the filamentous Anabaena sp. (Chaurasia & Apte, 2009;Rajaram & Apte, 2008). Nitrogen fixation has been similarly found to be sensitive to temperatures above 42 u C in the heterocystous cyanobacteria Anabaena cylindrica, Mastigocladus laminosus (Pederson et al, 1986), Anabaena sp.…”

Section: Introductionmentioning

confidence: 99%

Cyanobacterial heat-shock response: role and regulation of molecular chaperones

2014

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Cyanobacteria constitute a morphologically diverse group of oxygenic photoautotrophic microbes which range from unicellular to multicellular, and non-nitrogen-fixing to nitrogen-fixing types. Sustained long-term exposure to changing environmental conditions, during their three billion years of evolution, has presumably led to their adaptation to diverse ecological niches. The ability to maintain protein conformational homeostasis (folding-misfolding-refolding or aggregationdegradation) by molecular chaperones holds the key to the stress adaptability of cyanobacteria. Although cyanobacteria possess several genes encoding DnaK and DnaJ family proteins, these are not the most abundant heat-shock proteins (Hsps), as is the case in other bacteria. Instead, the Hsp60 family of proteins, comprising two phylogenetically conserved proteins, and small Hsps are more abundant during heat stress. The contribution of the Hsp100 (ClpB) family of proteins and of small Hsps in the unicellular cyanobacteria (Synechocystis and Synechococcus) as well as that of Hsp60 proteins in the filamentous cyanobacteria (Anabaena) to thermotolerance has been elucidated. The regulation of chaperone genes by several cis-elements and trans-acting factors has also been well documented. Recent studies have demonstrated novel transcriptional and translational (mRNA secondary structure) regulatory mechanisms in unicellular cyanobacteria. This article provides an insight into the heat-shock response: its organization, and ecophysiological regulation and role of molecular chaperones, in unicellular and filamentous nitrogen-fixing cyanobacterial strains.

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Section: Introductionmentioning

confidence: 99%

Cyanobacterial heat-shock response: role and regulation of molecular chaperones

2014

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“…Our recent work elucidated a major role of the cpn60 gene in the protection from photosynthesis and the nitrate reductase activity of N-supplemented Anabaena cultures (21). In this study, we integrated and constitutively overexpressed an extra copy of the groESL operon in Anabaena to evaluate the importance and contribution of GroEL chaperonin to the physiology of Anabaena during optimal and stressful conditions.…”

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“…One occurs as a solitary gene, cpn60 (17,21), while the other is juxtaposed to its cochaperonin encoding genes groES and constitutes a bicistronic operon groESL (7,19,31). The two hsp60 genes encode a 59-kDa GroEL and a 61-kDa Cpn60 protein in Anabaena (2,20).…”

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“…The growth of cyanobacterial cultures was estimated either by measuring the chlorophyll a content as described previously (18) or the turbidity (optical density at 750 nm). Photosynthesis was measured as light-dependent oxygen evolution at 25 Ϯ 2°C by a Clark electrode (Oxy-lab 2/2; Hansatech Instruments, England) as described previously (21). Nitrogenase activity was estimated by acetylene reduction assays, as described previously (3).…”

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Overexpression of the groESL Operon Enhances the Heat and Salinity Stress Tolerance of the Nitrogen-Fixing Cyanobacterium Anabaena sp. Strain PCC7120

Chaurasia

Apte

2009

Appl Environ Microbiol

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The bicistronic groESL operon, encoding the Hsp60 and Hsp10 chaperonins, was cloned into an integrative expression vector, pFPN, and incorporated at an innocuous site in the Anabaena sp. strain PCC7120 genome. In the recombinant Anabaena strain, the additional groESL operon was expressed from a strong cyanobacterial P psbA1 promoter without hampering the stress-responsive expression of the native groESL operon. The net expression of the two groESL operons promoted better growth, supported the vital activities of nitrogen fixation and photosynthesis at ambient conditions, and enhanced the tolerance of the recombinant Anabaena strain to heat and salinity stresses.

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“…Recently, we developed an integrative expression vector, pFPN (9), and demonstrated its utility for the aforesaid objectives (10,21). The vector pFPN integrates a strong light-inducible Anabaena promoter, P psbA1 , and a selectable gene, nptII, in the Anabaena genome at an innocuous intergenic region (Anabaena sp.…”

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Improved Eco-Friendly Recombinant Anabaena sp. Strain PCC7120 with Enhanced Nitrogen Biofertilizer Potential

Chaurasia

Apte

2011

Appl Environ Microbiol

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Photosynthetic, nitrogen-fixing Anabaena strains are native to tropical paddy fields and contribute to the carbon and nitrogen economy of such soils. Genetic engineering was employed to improve the nitrogen biofertilizer potential of Anabaena sp. strain PCC7120. Constitutive enhanced expression of an additional integrated copy of the hetR gene from a light-inducible promoter elevated HetR protein expression and enhanced functional heterocyst frequency in the recombinant strain. The recombinant strain displayed consistently higher nitrogenase activity than the wild-type strain and appeared to be in homeostasis with compatible modulation of photosynthesis and respiration. The enhanced combined nitrogen availability from the recombinant strain positively catered to the nitrogen demand of rice seedlings in short-term hydroponic experiments and supported better growth. The engineered strain is stable, eco-friendly, and useful for environmental application as nitrogen biofertilizer in paddy fields.

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Nitrogen status and heat-stress-dependent differential expression of the cpn60 chaperonin gene influences thermotolerance in the cyanobacterium Anabaena

Cited by 41 publications

References 29 publications

Cyanobacterial heat-shock response: role and regulation of molecular chaperones

Cyanobacterial heat-shock response: role and regulation of molecular chaperones

Overexpression of the groESL Operon Enhances the Heat and Salinity Stress Tolerance of the Nitrogen-Fixing Cyanobacterium Anabaena sp. Strain PCC7120

Improved Eco-Friendly Recombinant Anabaena sp. Strain PCC7120 with Enhanced Nitrogen Biofertilizer Potential

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