Diverse interactions of five core type III effectors from Ralstonia solanacearum with plants.

Ralstonia solanacearum is a widespread plant bacterial pathogen that can launch a range of type III effectors (T3Es) to cause disease. In this study, we isolate a pathogenic R. solanacearum strain named P380 from tomato rhizosphere. Five out of 12 core T3Es of strain P380 are introduced into Pseudomonas syringae DC3000D36E, separately, to determine their functions in interacting with plants. DC3000D36E that harbors each effector suppresses FliC-triggered Pti5 and ACRE31 expression, ROS burst, and callose deposition. RipAE, RipU, and RipW elicit cell death as well as up-regulate the MAPK cascades in Nicotiana benthamiana. The derivatives RipC1 and RipW but not RipAE fail to suppress ROS burst. Moreover, RipAE and RipW retain the cell death elicitation ability. RipAE and RipW are associate with salicylic acid and jasmonic acid pathways, respectively. RipAE and RipAQ significantly promote propagation of DC3000D36E in plants. The five core T3Es localize in diverse subcellular organelles of nucleus, plasma membrane (PM), endoplasmic reticulum (ER), and Golgi network. The suppressor of G2 allele of Skp1 (SGT1) is required for RipAE but not RipU-triggered cell death in N. benthamiana. These results indicate the core T3Es in R. solanacearum plays diverse roles in plant-pathogen interactions.