Heterocyst-Specific Excision of the Anabaena sp. Strain PCC 7120 hupL Element requires xisC
2005 (English)In: Journal of Bacteriology, Vol. 187, no 17, 6031-6038 p.Article in journal (Refereed) Published
In nitrogen-limiting conditions, approximately 10% of the vegetative cells in filaments of the cyanobacterium Anabaena (Nostoc) sp. strain PCC7120 differentiate into nitrogen-fixing heterocysts. During the late stages of heterocyst differentiation, three DNA-elements, each embedded within an open reading frame, are programmed to excise from chromosome by site-specific recombination. The DNA elements are named after the genes that they interrupt: nifD, fdxN, and hupL. The nifD and fdxN elements each contain a gene, xisA or xisF, respectively, that encodes the site-specific recombinase required for programmed excision of the element. Here, we show that the xisC gene (alr0677), which is present at one end of the 9,435-bp hupL element, is required for excision of the hupL element. A strain in which the xisC gene was inactivated showed no detactable excision of the hupL element. hupL encodes the large subunit of uptake of hydrogenase. The xisC mutant forms heterocysts and grows diazotrophically, but unlike the wild type, it evolved hydrogen gas under nitrogen-fixing conditions. Overexpression of xisC from a plasmid in the wild-type background caused a low level of hupL rearrangement even in nitrogen-replete conditions. Expression of xisC in Escherichia coli was sufficient to produce rearrangement of an artificial substrate plasmid bearing the hupL elemenat recombination sites. Sequence analysis indicated that XisC is a divergent member of the phage integrase family of recombinases. Site-directed mutagenesis of xisC showed that the XisC recombinase has functional silmilarity to the phage integrase family.
Place, publisher, year, edition, pages
2005. Vol. 187, no 17, 6031-6038 p.
IdentifiersURN: urn:nbn:se:uu:diva-76347DOI: doi:10.1128/JB.187.17.6031-6038.2005OAI: oai:DiVA.org:uu-76347DiVA: diva2:104259