Expression of the βhpmeh gene in transgenic events of the potato variety Desiree increases resistance to bacterial wilt caused by Ralstonia solanacearum

Abstract

Bacterial wilt, caused by the Ralstonia solanacearum species complex (RSSC), severely affects many important crops and significantly limits potato production worldwide. RSSC bacteria can regulate the expression of their virulence factors, including extracellular polysaccharides and endoglucanases, through quorum sensing, which enables bacteria to sense their population density through signaling molecules and collectively switch on virulence factors when a threshold density is reached. 3-hydroxy palmitic acid methyl ester is the main quorum-sensing molecule in RSSC that can be hydrolyzed by {beta}-hydroxypalmytate methyl ester hydrolase ({beta}HPMEH). In this study, we evaluated the ability of {beta}hpmeh transgenic potato (Desiree) plants to reduce bacterial wilt symptoms after artificial inoculation with two virulent RSSC strains under controlled conditions and related this to the expression of the {beta}hpmeh gene. For each transgenic event, we analyzed the phenotypic response (wilt incidence, latent infection, and area under the disease progress curve). Real-time quantitative PCR was performed to determine the relative expression levels of {beta}hpmeh in transgenic events. Several transgenic events were identified with reduced susceptibility to bacterial wilt compared to Desiree and a resistance level similar to or higher than that of potato variety Cruza 148, the most resistant variety available, which was positively correlated with {beta}hpmeh expression.