ProDH2 is induced by Pro and repressed by sucrose. Three-week-old wildtype (Col-8) or ProDH1-knockout mutant (pdh1-1) seedlings from sterile culture were transferred for 6 h to liquid half-strength MS medium with the indicated supplements prior to RNA extraction and northern blot analysis. The same membrane was hybridised consecutively with specific probes for ProDH2, P5CS1 and ProDH1. During the detection of P5CS1, no remainders of the ProDH2 specific signal were observed. The histogram above the northern blot panel indicates the intensity of the ProDH2-specific signal normalised to the level of Col-8 in medium with 30 mM sucrose.