The role of potassium as an ionic signal in the regulation of cyanobacterium Nostoc muscorum response to salinity and osmotic stress

Abstract

Spontaneously occurring thallium-resistant (Tl⁺-R) mutant of diazotrophic, heterocystous cyanobacterium Nostoc muscorum is described in which Tl⁺-R phenotype is the cause of defective salinity-inducible K⁺ uptake activity and proline uptake activity. The results indicate that mutant strain is more sensitive to salinity and osmotic stresses than its parent. The mutational inactivation of salinity-inducible proline uptake was found associated with increased sensitivity of the cyanobacterial photosynthetic O₂ evolution and nitrogenase activity under salinity and osmotic stresses. It is suggested that in the cyanobacterium Nostoc muscorum K⁺ functions as a primary osmolyte which is associated with salinity-inducible proline uptake leading to the acquisition of salt tolerance in the cyanobacterium. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)