Abstract
Some cyanobacteria accumulate sucrose as the compatible solute during salt stress. In Synechococcus elongatus PCC 6301/PCC 7942 and Thermosynechococcus elongatus BP-1, sucrose-phosphate synthase (SPS) and sucrose 6-phosphatase (SPS) genes are fused together and may function as the single polypeptide.
Effect of various salts to induce sucrose synthesis during the liquid culture of S. elongatus PCC 7942 was examined. Sucrose accumulation was hardly observed in low-salt conditions, but after the addition of 0.2 M NaCl, the intracellular sucrose concentration attained to approximately 160 mM within 24 hours. NaNO3 showed comparable effects as NaCl, while KCl and KNO3 were less effective.
The SPS-SPP gene in S. elongatus PCC 7942 was disrupted by targeted mutagenesis, resulting in the complete loss of the ability to synthesize sucrose. The growth rates of the mutant in the presence of 0.3 M NaCl were substantially reduced, indicating the significant role of the sugar under salt stress.
