Validation of an internal control gene to apply reverse transcription quantitative PCR to study heat, cold and ethanol stresses in Lactobacillus plantarum

The dissection of the stress tolerance in lactic acid bacteria (LAB) may improve our knowledge on the adaptive physiology of LAB and may facilitate the selection of species suitable for industrial application. In this work we report the validation of the ldhD gene as internal control for reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis in a model LAB such as Lactobacillus plantarum. The expression of the ldhD gene was analysed in lag phase, early, mid and late exponential phase and early and late stationary phase. Moreover, different stress conditions were analysed: heat shock (40°C), cold shock (10°C) and ethanolic shock (10% v/v). The quantification of transcript levels of a small heat shock gene (hsp 18.55) after heat, cold and ethanol shock allowed us to validate this method. RT-qPCR appeared as a powerful tool to study L. plantarum response in stress conditions and the internal control used in this study may be extended to other species of LAB.