Cloning of salinity stress-induced genes from the salt-tolerant nitrogen-fixing cyanobacterium Anabaena torulosa.

A subtractive hybridization procedure was used to clone genes of the cyanobacterium Anabaena torulosa expressed in response to salt stress. The method uses total RNA from salt-treated cells, labeled in vitro, as the probe. Hybridization to restriction digests of total DNA was used for interspecies comparison; the procedure was also successful for isolation of cosmids by colony hybridization, semiquantitative dot blots, and cosmid characterization by Southern blotting. Analysis of eleven independent cosmids containing genes whose transcription is abundantly induced by salt suggests that a substantial portion of the A. torulosa genome, probably in excess of 100 kilobases, responds to salt.