FIG. 4.

Effect of K⁺ limitation on Anabaena sp. strain L-31 kdp2 expression. (A) Anabaena sp. strain L-31 cells grown in BG-11/K5 were inoculated into BG-11 with different concentrations of external K⁺ and grown for 16 h. Total RNA (4 μg) was spotted onto nylon membrane and hybridized to the kdpA2 probe. (B) Anabaena sp. strain L-31 cells grown in BG-11/K5 were inoculated into BG-11/K0 medium, and the total RNA isolated at the indicated time points. At the end of 24 h, KCl (5 mM) was added to the medium (shown by an arrow), and the total RNA was isolated 0.5 and 1.0 h after K⁺ repletion. All of the RNA samples (4 μg each) were hybridized to the kdpA2 probe (upper panel) or the kdpA1 probe (lower panel).