Inactivation of tomato WAT1 leads to reduced susceptibility to Clavibacter michiganensis through downregulation of bacterial virulence factors

Abstract

Tomato bacterial canker caused by Clavibacter michiganensis (Cm) is considered to be one of the most destructive bacterial diseases of tomato. To date, no resistance to the pathogen has been identified. While several molecular studies have identified (Cm) bacterial factors involved in disease development, the plant genes and mechanisms associated with susceptibility of tomato to the bacterium remain largely unknown. Here, we show for the first time that tomato gene SlWAT1 is a susceptibility gene to Cm. We inactivated the gene SlWAT1 through RNAi and CRISPR/Cas9 to study changes in tomato susceptibility to Cm. Furthermore, we analysed the role of the gene in the molecular interaction with the pathogen. Our findings demonstrate that SlWAT1 functions as an S gene to genetically diverse Cm strains. Inactivation of SlWAT1 reduced free auxin contents and ethylene synthesis in tomato stems and suppressed the expression of specific bacterial virulence factors. However, CRISPR/Cas9 slwat1 mutants exhibited severe growth defects. The observed reduced susceptibility is possibly a result of downregulation of bacterial virulence factors and reduced auxin contents in transgenic plants. This shows that inactivation of an S gene may affect the expression of bacterial virulence factors.

Genetic and transcriptomic dissection of host defense to Goss's bacterial wilt and leaf blight of maize

“…All GA, JA, and ET were likely to be elevated upon Cn due to increased expression of multiple genes involved in their biosynthesis, including genes encoding ent-copalyl diphosphate synthase, ent-ekaurene oxidase (KO), and GA 2-oxidase for GA biosynthesis ( Sakamoto et al 2004 ); genes encoding allene oxide synthase and genes encoding lipoxygenases for JA biosynthesis ( Wasternack and Hause 2013 ); and genes encoding the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase and the ACC synthase family genes for ET biosynthesis ( Wang et al 2002 ). Consistently, a recent study also indicated the plant host manipulated the levels of auxin and ET to combat the clavibacter infection ( Koseoglou et al 2023 ). Fewer genes involved in brassinosteroid, cytokinin, and SA were induced by Cn ( Supplementary Fig.…”

“…Recently, Walls Are Thin1 ( WAT1 ) in tomato was shown to be a susceptibility gene to Cm. Inactivation of WAT1 enhanced tomato resistance to diverse Cm strains, likely through reducing auxin and ethylene (ET) content in plants, as well as suppressing the production of virulence factors in bacteria ( Koseoglou et al 2023 ).…”