DNA HELIX DESTABILIZATION BY PROLINE AND BETAINE - POSSIBLE ROLE IN THE SALINITY TOLERANCE PROCESS

Evidence is provided for the ability of proline, a salinity induced os moprotectant, to destabilize the double helix and lower the T-m of DNA in a concentration dependent manner, At the reported salinity-adaptiv e bio-accumulation of 1 M and above, proline could considerably decrea se the T-m and partially counteract the effect of sodium chloride and spermidine on DNA stability. On the contrary, several other amino acid s tested did not show any such destabilizing effect on DNA helix. Enha nced susceptibility to S1 nuclease and insensitivity to DNase I in pre sence of increasing proline concentrations have further suggested a cl ear destabilization of the double helix, Such an effect is somewhat re miniscent of the interaction between betaine, another salinity induced osmolyte, and DNA resulting in decreased T-m values. These interactio ns may be significant in view of the abundance of such osmolytes in ce lls under salinity stress-adapted conditions, with many a bacterial mu tant accumulating them exhibiting improved tolerance to salinity. (C) 1997 Federation of European Biochemical Societies.