MAPKKK5-induced cell death is independent of Ser-289 phosphorylation. Different MAPKKK5 variants were transiently expressed in N. benthamiana. The infiltrated leaves were photographed (left) and then stained with Trypan Blue (right) for observation of dead cells at 3 dpi. Similar cell death was induced in the leaves expressing MAPKKK5-YFP-HA, MAPKKK5S289A-YFP-HA, or MAPKKK5S289D-YFP-HA, but not in the leaves expressingMAPKKK5K375M-YFP-HA. 1, MAPKKK5-YFP-HA; 2, MAPKKK5K375M-YFP-HA; 3, MAPKKK5S289A-YFP-HA; 4, MAPKKK5S289D-YFP-HA.