A homozygous recA mutant of Synechocystis PCC6803: construction strategy and characteristics eliciting a novel RecA independent UVC resistance in dark

Minda, Renu; Ramchandani, Jyoti; Joshi, Vasudha; Bhattacharjee, S. K.

doi:10.1007/s00438-005-0054-z

Cited by 9 publications

(8 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All cyanobacteria possess a recA gene ( Acaryochoris marima MBIC11017 has 7 recA genes, Supplemental Table 1). The recA gene appeared to be indispensable to cell life in Synechococcus PCC7002 (Murphy et al, 1990), whereas it could be deleted from all chromosome copies in Synechocystis PCC6803 (Minda et al, 2005). The Synechocystis PCC6803 recA null mutant is bound to be of limited biotechnological interest because it is not only sensitive to UV-C, but also to standard fluence of white light required for cell growth.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Comparative Genomics of DNA Recombination and Repair in Cyanobacteria: Biotechnological Implications

2016

View full text Add to dashboard Cite

Cyanobacteria are fascinating photosynthetic prokaryotes that are regarded as the ancestors of the plant chloroplast; the purveyors of oxygen and biomass for the food chain; and promising cell factories for an environmentally friendly production of chemicals. In colonizing most waters and soils of our planet, cyanobacteria are inevitably challenged by environmental stresses that generate DNA damages. Furthermore, many strains engineered for biotechnological purposes can use DNA recombination to stop synthesizing the biotechnological product. Hence, it is important to study DNA recombination and repair in cyanobacteria for both basic and applied research. This review reports what is known in a few widely studied model cyanobacteria and what can be inferred by mining the sequenced genomes of morphologically and physiologically diverse strains. We show that cyanobacteria possess many E. coli-like DNA recombination and repair genes, and possibly other genes not yet identified. E. coli-homolog genes are unevenly distributed in cyanobacteria, in agreement with their wide genome diversity. Many genes are extremely well conserved in cyanobacteria (mutMS, radA, recA, recFO, recG, recN, ruvABC, ssb, and uvrABCD), even in small genomes, suggesting that they encode the core DNA repair process. In addition to these core genes, the marine Prochlorococcus and Synechococcus strains harbor recBCD (DNA recombination), umuCD (mutational DNA replication), as well as the key SOS genes lexA (regulation of the SOS system) and sulA (postponing of cell division until completion of DNA reparation). Hence, these strains could possess an E. coli-type SOS system. In contrast, several cyanobacteria endowed with larger genomes lack typical SOS genes. For examples, the two studied Gloeobacter strains lack alkB, lexA, and sulA; and Synechococcus PCC7942 has neither lexA nor recCD. Furthermore, the Synechocystis PCC6803 lexA product does not regulate DNA repair genes. Collectively, these findings indicate that not all cyanobacteria have an E. coli-type SOS system. Also interestingly, several cyanobacteria possess multiple copies of E. coli-like DNA repair genes, such as Acaryochloris marina MBIC11017 (2 alkB, 3 ogt, 7 recA, 3 recD, 2 ssb, 3 umuC, 4 umuD, and 8 xerC), Cyanothece ATCC51142 (2 lexA and 4 ruvC), and Nostoc PCC7120 (2 ssb and 3 xerC).

show abstract

Section: Resultsmentioning

confidence: 99%

“…So far, only the recA, ruvB , and lexA genes have been studied in vivo . The recA gene appeared to be indispensable in Synechococcus PCC7002 (Murphy et al, 1990), and dispensable in Synechocystis PCC6803 (Minda et al, 2005). The Synechocystis PCC6803 recA -null mutant was sensitive to UV-C and white light.…”

Section: Resultsmentioning

confidence: 99%

Comparative Genomics of DNA Recombination and Repair in Cyanobacteria: Biotechnological Implications

2016

View full text Add to dashboard Cite

show abstract

“…This was shown genetically, i.e. a knockout of the phrB gene conferred increased UV sensitivity to the organism, whereas a recA knockout mutant was still relatively resistant to UVC (Minda et al. , 2005).…”

Section: Discussionmentioning

confidence: 99%

UV hyper‐resistance in Prochlorococcus MED4 results from a single base pair deletion just upstream of an operon encoding nudix hydrolase and photolyase

Osburne

Holmbeck

Frias-Lopez

et al. 2010

Environmental Microbiology

View full text Add to dashboard Cite

Exposure to solar radiation can cause mortality in natural communities of pico-phytoplankton, both at the surface and to a depth of at least 30 m. DNA damage is a significant cause of death, mainly due to cyclobutane pyrimidine dimer formation, which can be lethal if not repaired. While developing a UV mutagenesis protocol for the marine cyanobacterium Prochlorococcus, we isolated a UV-hyper-resistant variant of high light-adapted strain MED4. The hyper-resistant strain was constitutively upregulated for expression of the mutT-phrB operon, encoding nudix hydrolase and photolyase, both of which are involved in repair of DNA damage that can be caused by UV light. Photolyase (PhrB) breaks pyrimidine dimers typically caused by UV exposure, using energy from visible light in the process known as photoreactivation. Nudix hydrolase (MutT) hydrolyses 8-oxo-dGTP, an aberrant form of GTP that results from oxidizing conditions, including UV radiation, thus impeding mispairing and mutagenesis by preventing incorporation of the aberrant form into DNA. These processes are error-free, in contrast to error-prone SOS dark repair systems that are widespread in bacteria. The UV-hyper-resistant strain contained only a single mutation: a 1 bp deletion in the intergenic region directly upstream of the mutT-phrB operon. Two subsequent enrichments for MED4 UV-hyper-resistant strains from MED4 wild-type cultures gave rise to strains containing this same 1 bp deletion, affirming its connection to the hyper-resistant phenotype. These results have implications for Prochlorococcus DNA repair mechanisms, genome stability and possibly lysogeny.

show abstract

“…Errors occurring during the nucleotide excision repair pathway (which is part of the error-prone SOS response) allow for all other mutations [6], [7], [8]. Pyrimidine dimers also lead to the formation of long single strand DNA, which activates RecA mediated homologous recombination [9], [10], [11].…”

Section: Introductionmentioning

confidence: 99%

The Optimal Mutagen Dosage to Induce Point-Mutations in Synechocystis sp. PCC6803 and Its Application to Promote Temperature Tolerance

et al. 2012

View full text Add to dashboard Cite

Random mutagenesis is a useful tool to genetically modify organisms for various purposes, such as adaptation to cultivation conditions, the induction of tolerances, or increased yield of valuable substances. This is especially attractive for systems where it is not obvious which genes require modifications. Random mutagenesis has been extensively used to modify crop plants, but even with the renewed interest in microalgae and cyanobacteria for biofuel applications, there is relatively limited current research available on the application of random mutagenesis for these organisms, especially for cyanobacteria. In the presented work we characterized the lethality and rate of non-lethal point mutations for ultraviolet radiation and methyl methanesulphonate on the model cyanobacteria Synechocystis sp. PCC6803. Based on these results an optimal dosage of 10–50 J/m2 for UV and either 0.1 or 1 v% for MMS was determined. A Synechocystis wildtype culture was then mutagenized and selected for increased temperature tolerance in vivo. During the second round of mutagenesis the viability of the culture was monitored on a cell by cell level from the treatment of the cells up to the growth at an increased temperature. After four distinct rounds of treatment (two with each mutagen) the temperature tolerance of the strain was effectively raised by about 2°C. Coupled with an appropriate in vivo screening, the described methods should be applicable to induce a variety of desirable characteristics in various strains. Coupling random mutagenesis with high-throughput screening methods would additionally allow to select for important characteristics for biofuel production, which do not yield a higher fitness and can not be selected for in vivo, such as fatty acid concentration. In a combined approach with full genome sequencing random mutagenesis could be used to determine suitable target-genes for more focused methods.

show abstract

A homozygous recA mutant of Synechocystis PCC6803: construction strategy and characteristics eliciting a novel RecA independent UVC resistance in dark

Cited by 9 publications

References 48 publications

Comparative Genomics of DNA Recombination and Repair in Cyanobacteria: Biotechnological Implications

Comparative Genomics of DNA Recombination and Repair in Cyanobacteria: Biotechnological Implications

UV hyper‐resistance in Prochlorococcus MED4 results from a single base pair deletion just upstream of an operon encoding nudix hydrolase and photolyase

The Optimal Mutagen Dosage to Induce Point-Mutations in Synechocystis sp. PCC6803 and Its Application to Promote Temperature Tolerance

Contact Info

Product

Resources

About