The YdaO/YuaA leader (now called the cyclic di-AMP riboswitch) is a conserved RNA structure found upstream of the ydaO and yuaA genes in Bacillus subtilis and related genes in other bacteria.
The regulatory element controlling the expression of ydaO and yuaA genes, now referred to as the cyclic di-AMP riboswitch, is a stable RNA structure found preceding these genes in Bacillus subtilis and similar genes in other bacterial species.