Plant material

As previously described, mutant and wild-type seeds were sterilized and sown on Murashige and Skoog plates [26], supplemented with the appropriate antibiotic under a light period of 16 h (71 μmol m⁻² s⁻¹) at 21°C. Arabidopsis mutant (vad1-1) and other transgenic lines used in this study (35S::RFP::VAD1, 35S::RFP::ΔGRAM, 35S::RFP::ΔVASt) are in the WS-4 or vad1-1 background and were grown respectively in presence of kanamycin 50 μg mL⁻¹ for the vad1-1 mutant or hygromycin 25 μg mL⁻¹ for the transgenic lines.

7 to 10 days after sowing, seedlings were transplanted to Jiffy pots and grown in a growth chamber under a light period of 9 h (192 μmol m⁻² s⁻¹) at 21°C and 40% to 70% relative humidity and4- to 5-week old plants were used for most experiments. Under these growth conditions, lesions appear on the vad1-1 mutant 21 days after transplanting.