Trehalose is a natural sugar that is important for plant development and abiotic stress tolerance. It is an important metabolic signal that regulates gene expression and is associated with diverse processes in plants. However, it remained unclear as to whether trehalose metabolism regulates responses to pathogens in Arabidopsis thaliana. 

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to analyze the function of a class II TPS (trehalose 6-phospate synthase) and the role of trehalose metabolism in plant defense responses. 

They demonstrated that TREHALOSE PHOSPHATE SYNTHASE 5 (TPS5)‐dependent trehalose metabolism regulates Arabidopsis thaliana defenses against pathogens (necrotrophic Botrytis cinerea and biotrophic Pseudomonas syringae).  

Following a pre-treatment with trehalose prior to infection by B. cinerea, the researchers observed a decrease in disease symptoms, including the number of lesions. It indicated that trehalose can interfere with fungal infection and, thereby, restrict fungal growth. The insertion of T-DNA fragments into TPS5 resulted in decreased resistance to B. cinerea. 

They also observed a transient increase in trehalose levels in wild-type plants, but not in tps5 mutant plants. These results suggest that TPS5 is required for A. thaliana defenses against B. cinerea. 

Pathogen infection increased trehalose levels and up- regulated TPS5 expression. The application of exogenous trehalose significantly improved plant defenses against B. cinerea, but increased the susceptibility of plants to P. syringae. 

Furthermore, TPS5-dependent trehalose metabolism can positively regulate A. thaliana resistance to B. cinerea, whereas it negatively regulates defense responses to P. syringae. 

The study entitled "Trehalose phosphate synthase 5‐dependent trehalose metabolism modulates basal defense responses in Arabidopsis thaliana" has been published in Journal of Integrative Plant Biology.