Publications by authors named "Randi M Aamodt"

6 Publications

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Somatic maintenance resources in the honeybee worker fat body are distributed to withstand the most life-threatening challenges at each life stage.

PLoS One 2013 5;8(8):e69870. Epub 2013 Aug 5.

Department of Aquaculture and Animal Sciences, Norwegian University of Life Sciences, Aas, Norway.

In a global transcriptome analysis of three natural and three manipulated honeybee worker phenotypes at different ages, we have investigated the distribution of investment in somatic maintenance of the fat body. Gene expression is modulated so that the bees are able to resist the most life-threatening challenges at the actual life stage. Different modes of maintenance and repair are regulated, apparently to meet the environmental challenges most detrimental to survival and reproductive potential for the hive. We observed a broad down-regulation of genomic and cellular maintenance in the short-lived foragers and nurse bees compared to the long-lived winter bees. Our results show that survival and reproduction of the entire hive is given priority over the individual bees, hence supporting the idea of the honeybee society as a superorganism. Our results also fit the disposable soma theory of aging.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0069870PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3734224PMC
March 2014

The ada operon of Mycobacterium tuberculosis encodes two DNA methyltransferases for inducible repair of DNA alkylation damage.

DNA Repair (Amst) 2011 Jun 12;10(6):595-602. Epub 2011 May 12.

Department of Microbiology, Oslo University Hospital, Rikshospitalet, PO Box 4950 Nydalen, NO-0424 Oslo, Norway.

The ada operon of Mycobacterium tuberculosis, which encodes a composite protein of AdaA and AlkA and a separate AdaB/Ogt protein, was characterized. M. tuberculosis treated with N-methyl-N'-nitro-N-nitrosoguanidine induced transcription of the adaA-alkA and adaB genes, suggesting that M. tuberculosis mount an inducible response to methylating agents. Survival assays of the methyltransferase defective Escherichia coli mutant KT233 (ada ogt), showed that expression of the adaB gene rescued the alkylation sensitivity. Further, adaB but not adaA-alkA complemented the hypermutator phenotype of KT233. Purified AdaA-AlkA and AdaB possessed methyltransferase activity. These data suggested that AdaB counteract the cytotoxic and mutagenic effect of O(6)-methylguanine, while AdaA-AlkA most likely transfers methyl groups from innocuous methylphosphotriesters. AdaA-AlkA did not possess alkylbase DNA glycosylase activity nor rescue the alkylation sensitivity of the E. coli mutant BK2118 (tag alkA). We propose that AdaA-AlkA is a positive regulator of the adaptive response in M. tuberculosis. It thus appears that the ada operon of M. tuberculosis suppresses the mutagenic effect of alkylation but not the cytotoxic effect of lesions such as 3-methylpurines. Collectively, these data indicate that M. tuberculosis hypermutator strains with defective adaptive response genes might sustain robustness to cytotoxic alkylation DNA damage and confer a selective advantage contributing to host adaptation.
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http://dx.doi.org/10.1016/j.dnarep.2011.03.007DOI Listing
June 2011

Age-and caste-dependent decrease in expression of genes maintaining DNA and RNA quality and mitochondrial integrity in the honeybee wing muscle.

Authors:
Randi M Aamodt

Exp Gerontol 2009 Sep 27;44(9):586-93. Epub 2009 Jun 27.

Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Aas, Norway.

I report here an investigation of the age- and caste-specific expression patterns of nine honeybee orthologs of genes involved in repair of oxidative and methylation damage of DNA, and possibly RNA, in wing muscle tissue of the honeybee Apis mellifera. mRNA expression levels were measured in a comparative study of queens and ageing workers. Two of these genes, both potentially involved in repair and prevention of oxidative damage, showed higher expression in queens than workers and a distinct downregulation during the ageing trajectory in workers. These were an ortholog of mammalian NTH1 and a gene encoding a fusion protein which seems to be unique for the honeybee, consisting of one domain homologous to mammalian MTH1/Nudix/bacterial mutT and another domain homologous to the mitochondrial ribosomal protein gene S23. Orthologs of aag, apn1, msh6, ogg1, smug1 and two orthologs of human ABH/E. coli alkB, had stable expression levels during the ageing trajectory except high apn1 levels in overwintering workers. To estimate eventual age-dependent mitochondrial maintenance, batches of mitochondrial DNA from young and old workers and young queens were re-sequenced using Solexa/Illumina high-throughput sequencing. The results indicate at least a 50% reduction of intact mitochondrial fragments in foragers compared to young workers, winter bees and queens.
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http://dx.doi.org/10.1016/j.exger.2009.06.004DOI Listing
September 2009

The caste- and age-specific expression signature of honeybee heat shock genes shows an alternative splicing-dependent regulation of Hsp90.

Authors:
Randi M Aamodt

Mech Ageing Dev 2008 Nov 6;129(11):632-7. Epub 2008 Aug 6.

Department of Animal and Aquacultural Sciences and Centre for Integrative Genetics, Norwegian University of Life Sciences, N-1432 Aas, Norway.

I report the investigation of the age- and caste-specific expression patterns of eight genes involved in protein maintenance and repair in wing muscle tissue of the honeybee Apis mellifera. mRNA levels of seven heat shock genes and the protein repair gene pcmt (encoding L-isoaspartyl-O-methyltransferase) were measured in a comparative study of queens and ageing workers. Two hsp90 orthologs, transcribed from the same locus, showed different age- and caste-dependent expression patterns suggesting an alternative splicing-dependent regulatory mechanism. One transcript showed decreasing expression levels with worker age and four times higher levels in queens than workers on average, while the other variant had much higher and even expression levels. An hsp22-like gene was sevenfold upregulated in workers from the newly emerged-stage and showed an age-dependent decreasing slope for the subsequent stages. Honeybee ageing seems therefore not to be accompanied by increase in the heat shock response at the level of gene expression. The method used provides very sensitive measurements of a limited number of genes, and this study is one of the first of the regulation of expression of protein protection and repair genes during aging, performed in an un-manipulated model organisms living in a natural environment.
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http://dx.doi.org/10.1016/j.mad.2008.07.002DOI Listing
November 2008

Long-term maintenance of in vitro cultured honeybee (Apis mellifera) embryonic cells.

BMC Dev Biol 2006 Mar 17;6:17. Epub 2006 Mar 17.

Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, 1432 Aas, Norway.

Background: In vitro cultivation of cells allows novel investigation of in vivo- mechanisms and is a helpful tool in developmental biology, biochemistry and functional genomics. Numerous cell lines of insect species, e.g., silkworm and mosquito, have been reported. However, this is not the case for successful long-term cultivation of cells in honeybees.

Results: Methods for cultivation of honeybee embryonic cells are discussed here. Pre-gastrula stage embryos were used to initiate cultures, and cells were reared on 96-wells microplates with Grace insect medium, supplemented with Fetal Bovine Serum. Cells proliferated in clusters, and maintained viable and mitotic for more than three months.

Conclusion: We report here, for the first time, long-term cultivation of honeybee cells. Results represent a highly useful in vitro-system for studying a model organism of increasing importance in areas such as aging, sociality and neurobiology.
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http://dx.doi.org/10.1186/1471-213X-6-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1434730PMC
March 2006

The Bacillus subtilis counterpart of the mammalian 3-methyladenine DNA glycosylase has hypoxanthine and 1,N6-ethenoadenine as preferred substrates.

J Biol Chem 2004 Apr 16;279(14):13601-6. Epub 2004 Jan 16.

Department of Molecular Biology, Institute of Medical Microbiology, University of Oslo, National Hospital, N-0027 Oslo, Norway.

The AAG family of 3-methyladenine DNA glycosylases was initially thought to be limited to mammalian cells, but genome sequencing efforts have revealed the presence of homologous proteins in certain prokaryotic species as well. Here, we report the first molecular characterization of a functional prokaryotic AAG homologue, i.e. YxlJ, termed bAag, from Bacillus subtilis. The B. subtilis aag gene was expressed in Escherichia coli, and the protein was purified to homogeneity. As expected, B. subtilis Aag was found to be a DNA glycosylase, which releases 3-alkylated purines and hypoxanthine, as well as the cyclic etheno adduct 1,N(6)-ethenoadenine from DNA. However, kinetic analysis showed that bAag removed hypoxanthine much faster than human AAG with a 10-fold higher value for k(cat), whereas the rate of excision of 1, N(6)-ethenoadenine was found to be similar. In contrast, it was found that bAag removes 3-methyladenine and 3-methylguanine approximately 10-20 times more slowly than human AAG, and there was hardly any detectable excision of 7-methylguanine. It thus appears that bAag has a minor role in the repair of DNA alkylation damage and an important role in preventing the mutagenic effects of deaminated purines and cyclic etheno adducts in Bacillus subtilis.
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http://dx.doi.org/10.1074/jbc.M314277200DOI Listing
April 2004
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