To evaluate the role of HrcA and CtsR in ethanol tolerance, ctsR and hrcA gene deletion mutants were constructed. The growth rate of the L. plantarum ΔctsR::cat strain was impaired in de Man-Rogosa-Sharpe (MRS) medium containing 8% ethanol, whereas growth of the L. plantarum ΔhrcA::cat and ΔctsR ΔhrcA::cat mutants was indistinguishable from that of wild-type cells. Overall, these results suggest that the induction of CtsR class III stress responses provides cross-protection against heat stress.