Isolation of a novel SUMO protein from tomato that suppresses EIX‐induced cell death

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Abstract
Summary: Challenging tomato or tobacco varieties with ethylene‐inducing xylanase (EIX) from the fungus Trichoderma viride causes rapid induction of plant defence responses leading to programmed cell death. Using the yeast two‐hybrid system, we isolated a novel protein, tomato small ubiquitin‐related modifier protein (T‐SUMO), which specifically interacts with EIX. T‐SUMO, a cytoplasmic protein, is a member of the ubiquitin‐like protein family. It shows homology to human protein sentrin/SUMO1, which suppresses tumour necrosis factor‐induced cell death. Transgenic plants that express T‐SUMO in the sense orientation suppress EIX induction of ethylene biosynthesis and cell death, while in the antisense orientation they enhance EIX‐induced ethylene biosynthesis. These results indicate that T‐SUMO is involved in mediating the signal generated by EIX that leads to induction of plant defence responses.