Protein preparation and western blot analysis
The Arabidopsis proteins were extracted by using Plant Protein Extraction Kit (Solarbio, Beijing, China). 15 µg protein was loaded to 7.5%, 1.5 mM SDS-gels. To measure ICE1 protein, the Anti-ICE1 (1:1000, Agrisera) was used as primary antibody. Anti-Actin (1:1000, Abmart) was used as loading control for ICE1. For all western blots, HRP-anti-rabbit & mouse was used as secondary antibody (1:10000; Abmart). Imaging was carried out using a cooled CCD camera system (Polychromatic fluorescence / chemiluminescence gel imaging system, UVITEC) and Western blots were quantified with Q9 Aliance software.