532 / 2019-03-13 09:59:24

A Ralstonia solanacearum effector hijacks plant metabolism to support bacterial nutrition

Ralstonia, GABA, plant metabolism, bacterial wilt

全体主题 > Plant Microbe Interactions & Microbiomes

Ralstonia solanacearum, a widely distributed, destructive, Gram-negative, soil-borne phytopathogen, able to cause disease in more than 250 plant species, including economically important crops, such as tomato, potato, banana, ginger, pepper and tobacco, posing a huge threat to global food security. Here we report a Ralstonia secreted protein Rip19, which is required for full Ralstonia virulence and shows activity to promote GABA biosynthesis in planta. We found that Rip19 associates with Calmodulin, an essential regulator for the activation of glutamate decarboxylase (GAD), the key enzyme in GABA biosynthesis. GABA, on one hand, can be used as a nutrient by Ralstonia, and, on the other, it is stress-signaling molecule for plants in response to both biotic and abiotic stress. In vitro and in vivo biochemical assays suggest that Rip19 associates with GAD and promotes the CaM binding to GAD. The GABA-deficient Arabidopsis gad1/2 mutant surprisingly shows enhanced resistance to Ralstonia infection but not to Pseudomonas syringae infection. Taken together, our work shows that Rip19 is a novel uncharacterized effector that hijacks plant GABA signaling to support bacterial nutrition and potentially suppress plant immunity. These findings give clues for developing novel strategies to generate Ralstonia-resistant crops.