The EF-Tu epitope elf26 of Ralstonia solanacearum can promote resistance to bacterial wilt disease in Nicotiana species

Elongation factor Tu (EF-Tu) from bacterial plant pathogens acts as a pathogen-associated molecular pattern (PAMP), which elicits the first line of defence of innate immunity. Ralstonia solanacearum is the causal agent of bacterial wilt in many Solanaceous plants, including Nicotiana tabacum and N. benthamiana. Here, we report that R. solanacearum EF-Tu can promote the resistance of Nicotiana plants to wilt disease. A synthetic elf26 epitope of R. solanacearum EF-Tu induced a clear accumulation of callose and hydrogen peroxide in Arabidopsis thaliana. It was very striking that elf26 induced the expression of PTI marker genes as well as a low dose of callose and hydrogen peroxide accumulation in N. tabacum as EF-Tu triggering innate immunity was previously considered to be Brassicaceae specific. Although innate immunity was not found in N. benthamiana, the defence-related PR1a gene was induced. Thus, elf26 treatments enhanced the resistance of N. tabacum and N. benthamiana plants to R. solanacearum. Together, our findings demonstrated that the R. solanacearum elf26 epitope functions as a PAMP and can promote resistance to bacterial wilt disease in Nicotiana spp.