Figure 1.

Effect of heat stress on the levels of free SUMO and SUMO conjugates in Arabidopsis. (A) Profile of SUMO conjugates in seedlings before and after heat stress. Seven-day-old seedlings were grown at 24°C, exposed to 37°C for 30 min, and then returned to 24°C for 30 min before harvest. Crude protein extracts were subjected to SDS-PAGE and immunoblot analysis with anti-SUMO1 antibodies. Levels of the proteasome subunit PBA1 were used to confirm equal loading. HS, heat-stressed seedlings. RT, seedlings not exposed to heat stress. (B) Quantification of high molecular mass SUMO conjugates and free SUMO. Levels of each fraction were quantified by densitometric scanning of the immunoblot membranes probed with anti-SUMO1 antibodies. Error bars represent the standard deviation of three independent heat-stress experiments.