A sugar-binding protein helps a tomato pathogen multiply in leaves

What the study found

Deng and Kim used base editing to make mutants in six candidate sucrose-utilization genes in Pseudomonas syringae pv. tomato DC3000. The bacterium is associated with bacterial speck disease. The authors report that loss of ThuE, a substrate-binding protein in the space between the bacterium’s membranes, impaired growth both in laboratory conditions and in plants. In tomato leaves, populations of the ThuE mutant were approximately two orders of magnitude lower.

Other gene disruptions had different effects. Loss of the sucrose hydrolase ScrB or both levansucrases had no detectable effect. A growth defect in a mutant lacking the outer-membrane porin ScrY was overcome by increasing external sucrose.

Why it matters

Sucrose is abundant in the leaf apoplast, the space outside plant cells. The authors conclude that sucrose import through a single, non-redundant inner-membrane ABC transporter is required for multiplication in leaves. They suggest this pathway could be a potential target for controlling bacterial speck disease.

Limits and unknowns

This is a bioRxiv preprint, and the available source is its abstract. The abstract does not provide experimental conditions, sample sizes, statistical uncertainty or details of how sucrose uptake was measured. It also does not establish whether targeting the pathway would control disease in practice.