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Improved eco-friendly recombinant Anabaena sp. strain PCC7120 with enhanced nitrogen biofertilizer potential.

ABSTRACT: 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.

SUBMITTER: Chaurasia AK

PROVIDER: S-EPMC3020549 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Improved eco-friendly recombinant Anabaena sp. strain PCC7120 with enhanced nitrogen biofertilizer potential.

Chaurasia Akhilesh Kumar AK Apte Shree Kumar SK

Applied and environmental microbiology 20101105 2

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 s ...[more]

PMID: 21057013

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Project description:Anabaena (also Nostoc) sp. strain PCC7120, hereafter Anabaena, is a cyanobacterium that fixes atmospheric N2 in specialized cells called heterocysts. Heterocyst differentiation is regulated by a homodimeric transcription factor, HetR. HetR is expressed at a basal level in all cells but its expression increases in differentiating cells early after nitrogen deprivation. HetR is required for heterocyst development, and therefore nitrogen fixation and diazotrophic growth. Overexpression of HetR leads to multiple contiguous heterocysts (Mch phenotype). HetR binds in vitro to DNA fragments upstream of several genes upregulated in heterocysts, including hetZ, hetP, hepA, patS, pknE, and hetR itself. HetR binds an inverted repeat sequence upstream of a few of these genes; however, HetR binds to promoters that do not contain this sequence, such as the promoter regions for patS and pknE.We employed chromatin pull-down and deep sequencing (ChIP-seq) to globally identify HetR DNA targets in vivo at six hours after fixed-nitrogen deprivation. We identified novel DNA binding targets of tagged HetR-6xHis and defined a consensus HetR binding site from these HetR target sequences. Promoter-gfp reporter fusions were used to determine the spatiotemporal expression of four potential HetR-target genes. The promoter region for asr1469 was expressed transiently in differentiating heterocysts, alr3758 was upregulated in heterocysts, asl2028 was expressed in vegetative cells, and alr2242 was derepressed in vegetative cells of a hetR mutant strain.In addition to identifying known HetR target genes hetR and hetP, the ChIP-seq data were used to identify new potential HetR targets and to define a consensus HetR-binding site. The in vivo ChIP-seq analysis of HetR's regulon suggests a possible role for HetR in vegetative cells in addition to its role in heterocyst development. The potential HetR target genes identified in this study provide new subjects for future work on the role of HetR in gene regulation.

Dataset Information

Improved eco-friendly recombinant Anabaena sp. strain PCC7120 with enhanced nitrogen biofertilizer potential.

Publications

Improved eco-friendly recombinant Anabaena sp. strain PCC7120 with enhanced nitrogen biofertilizer potential.

Similar Datasets

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