elicitor RipX Induces Defense Reaction by Suppressing the Mitochondrial Gene in Host Plant.

RipX of is translocated into host cells by a type III secretion system and acts as a harpin-like protein to induce a hypersensitive response in tobacco plants. The molecular events in association with RipX-induced signaling transduction have not been fully elucidated. This work reports that transient expression of RipX induced a yellowing phenotype in , coupled with activation of the defense reaction. Using yeast two-hybrid and split-luciferase complementation assays, mitochondrial ATP synthase F1 subunit α (ATPA) was identified as an interaction partner of RipX from . Although a certain proportion was found in mitochondria, the YFP-ATPA fusion was able to localize to the cell membrane, cytoplasm, and nucleus. RFP-RipX fusion was found from the cell membrane and cytoplasm. Moreover, ATPA interacted with RipX at both the cell membrane and cytoplasm in vivo. Silencing of the gene had no effect on the appearance of yellowing phenotype induced by RipX. However, the silenced plants improved the resistance to Moreover, qRT-PCR and promoter GUS fusion experiments revealed that the transcript levels of were evidently reduced in response to expression of RipX. These data demonstrated that RipX exerts a suppressive effect on the transcription of gene, to induce defense reaction in .