Organization and Regulation of Two Clusters of nif Genes in the Cyanobacterium Anabaena Variabilis

Thiel, Teresa; Lyons, Eilene M.; Thielemeier, Jessica

doi:10.1007/978-1-4615-4827-0_59

Cited by 4 publications

(10 citation statements)

References 16 publications

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“…During anaerobic growth, the transcription of nif genes occurs in all cells of Anabaena 7120, whereas the transcription of rbcLS occurs in none (Madan & Nierzwicki-Bauer, 1993). Under similar conditions, a second nitrogenase (nif 2) is induced in vegetative cells of Anabaena variabilis (Thiel et al, 1999). This pattern differs from that in aerobically grown cultures, in which nitrogenase occurs only in heterocysts and Rubisco is confined to vegetative cells.…”

Section: Microaerobiosismentioning

confidence: 89%

Tansley Review No. 116

2000

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Summary 449 I. INTRODUCTION 450 II. THE PARTNERS 451 1. Cyanobionts and their role 451 2. Hosts and their role 453 3. Location of cyanobionts in their hosts 455 III. INITIATION AND DEVELOPMENT OF SYMBIOSES 458 1. Initiation of symbioses 458 2. Geosiphon pyriforme 458 3. Cyanolichens 459 4. Liverworts and hornworts 460 5. Azolla 460 6. Cycads 461 7. Gunnera 461 IV. THE SYMBIOSES 462 1. Geographical distribution and ecological significance 462 2. Benefits to the partners 462 (a) Benefits to the cyanobionts 462 (b) Benefits to the hosts 463 3. Duration and stability 463 4. Mode of transmission and perpetuation 463 5. Recognition between the partners 464 6. Specificity and diversity 464 7. Symbiosis‐related genes 465 8. Modifications of the cyanobiont 466 (a) Growth and morphology 466 (b) Photosynthesis and carbon metabolism 467 (c) Glutamine synthetase 467 (d) Heterocysts 469 (e) N2fixation 470 9. Nutrient exchange 471 (a) Carbon 471 (b) Nitrogen 472 V. EVOLUTIONARY ASPECTS 472 VI. ARTIFICIAL SYMBIOSES 474 VII. FUTURE OUTLOOK AND PERSPECTIVES 475 1. Cryptic symbioses 476 2. Developmental profile of symbiotic tissues 476 3. Sensing and signalling 476 4. Genetic aspects 476 5. Physiological and biochemical aspects of nutrient exchange 477 6. Microaerobiosis 477 7. Potential applications 477 Acknowledgements 477 References 477 Cyanobacteria are an ancient, morphologically diverse group of prokaryotes with an oxygenic photosynthesis. Many cyanobacteria also possess the ability to fix N2. Although well suited to an independent existence in nature, some cyanobacteria occur in symbiosis with a wide range of hosts (protists, animals and plants). Among plants, such symbioses have independently evolved in phylogenetically diverse genera belonging to the algae, fungi, bryophytes, pteridophytes, gymnosperms and angiosperms. These are N2‐fixing symbioses involving heterocystous cyanobacteria, particularly Nostoc, as cyanobionts (cyanobacterial partners). A given host species associates with only a particular cyanobiont genus but such specificity does not extend to the strain level. The cyanobiont is located under a microaerobic environment in a variety of host organs and tissues (bladder, thalli and cephalodia in fungi; cavities in gametophytes of hornworts and liverworts or fronds of the Azolla sporophyte; coralloid roots in cycads; stem glands in Gunnera). Except for fungi, the hosts form these structures ahead of the cyanobiont infection. The symbiosis lasts for one generation except in Azolla and diatoms, in which it is perpetuated from generation to generation. Within each generation, multiple fresh infections occur as new symbiotic tissues and organs develop. The symbioses are stable over a wide range of environmental conditions, and sensing–signalling between partners ensures their synchronized growth and development. The cyanobiont population is kept constant in relation to the host biomass through controlled initiation and infection, nutrient supply and cell division. In most cases, the partners have remaine...

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Section: Microaerobiosismentioning

confidence: 89%

Tansley Review No. 116

2000

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“…In Anabaena variabilis ATCC 29413 there are three clusters of genes that control N # fixation, nif1, nif2 and vnf (Schrautemeier et al, 1995 ;Thiel et al, 1999). The first of these is the homologue of the nif cluster in Anabaena PCC 7120, and is similarly interrupted by an 11 kb excision element, but lacks the 55 kb element (see section III.4.(e)).…”

Section: Heterocyst Developmentmentioning

confidence: 99%

“…Inactivation of the xisF gene prevents N # fixation, but has no effect on heterocyst differentiation and pattern (Carrasco et al, 1994). Indeed, both the 11-kb (Oxelfelt et al, 1998 ;Bo$ hme, 1998) and the 55-kb (Haselkorn, 1992 ;Thiel et al, 1999) elements are absent from the genomes of a number of Anabaena and Nostoc strains.…”

Section: Heterocyst Developmentmentioning

confidence: 99%

Tansley Review No. 107. Heterocyst and akinete differentiation in cyanobacteria

1999

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“…Direction of transcription is indicated by arrows. Physical maps of the nif1 (C) and nif 2 gene (D) clusters of A. variabilis (adapted and modified from Thiel et al 1999 are shown for comparison.…”

Section: Resultsmentioning

confidence: 99%

“…It has been suggested that nif 2 genes are regulated primarily by environmental factors, in contrast to the developmentally regulated heterocyst nif1 genes (Thiel et al 1995), and that the nif 2 genes of A. variabilis , which are expressed in vegetative cells, are related to the nif genes of Plectonema boryanum (Thiel et al 1997). It has also been suggested that the nif 2 genes evolved with a regulatory system different from that of the nif 1 genes (Thiel et al 1999). The organization of the major nif gene cluster has been characterized in the filamentous heterocystous cyanobacteria Anabaena spp.…”

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confidence: 99%

ORGANIZATION OF THE nif GENES OF THE NONHETEROCYSTOUS CYANOBACTERIUM TRICHODESMIUM SP. IMS101

Dominic

Zani

Chen

et al. 2000

Journal of Phycology

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An approximately 16-kb fragment of the Trichodesmium sp. IMS101 (a nonheterocystous filamentous cyanobacterium) "conventional"nif gene cluster was cloned and sequenced. The gene organization of the Trichodesmium and Anabaena variabilis vegetative (nif 2) nitrogenase gene clusters spanning the region from nif B to nif W are similar except for the absence of two open reading frames (ORF3 and ORF1) in Trichodesmium. The Trichodesmium nif EN genes encode a fused Nif EN polypeptide that does not appear to be processed into individual Nif E and Nif N polypeptides. Fused nif EN genes were previously found in the A. variabilis nif 2 genes, but we have found that fused nif EN genes are widespread in the nonheterocystous cyanobacteria. Although the gene organization of the nonheterocystous filamentous Trichodesmium nif gene cluster is very similar to that of the A. variabilis vegetative nif 2 gene cluster, phylogenetic analysis of nif sequences do not support close relatedness of Trichodesmium and A. variabilis vegetative (nif 2) nitrogenase genes.

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Organization and Regulation of Two Clusters of nif Genes in the Cyanobacterium Anabaena Variabilis

Cited by 4 publications

References 16 publications

Tansley Review No. 116

Tansley Review No. 116

Tansley Review No. 107. Heterocyst and akinete differentiation in cyanobacteria

ORGANIZATION OF THE nif GENES OF THE NONHETEROCYSTOUS CYANOBACTERIUM TRICHODESMIUM SP. IMS101

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