Galactose transporters VfSWEET19 and VfSWEET26 attenuate plant immunity but enhance drought and salt tolerance

Highlights 1 • This study identified 27 members of the SWEET gene family in faba bean and revealed that the VfSWEET members demonstrated spatio-temporal expression patterns under abiotic stress. • Functional studies revealed that VfSWEET19 and VfSWEET26 , which encode plasma membrane-localized galactose transporters, are involved in susceptibility to pathogen infection and INF1-triggered cell death. • Conversely, overexpression of VfSWEET19 and VfSWEET26 significantly enhanced drought and salt tolerance by modulating stomatal aperture and scavenging reactive oxygen species (ROS). Faba bean is a vital food and industrial crop, yet its production is increasingly threatened by various stresses. SWEETs, a class of plant-specific genes, play essential roles in plant stress responses. However, knowledge regarding Vicia faba SWEETs remains limited. In this study, 27 VfSWEETs were identified from the faba bean genome. A comprehensive analysis revealed that these genes are under strong purifying selection and primarily encode hydrophobic proteins localized to the plasma membrane, featuring the characteristic MtN3_slv domain. Promoters of VfSWEETs were found to contain numerous stress-responsive cis -elements, suggesting their involvement in stress responses and growth regulation in faba bean. Notably, VfSWEET19 and VfSWEET26 were upregulated under drought and salt stress; both encode plasma membrane-localized galactose transporters. These transporters attenuate plant immunity by inhibiting pattern-triggered immunity (PTI) and disrupting ROS homeostasis, thereby facilitating pathogen infection. Additionally, they enhance drought and salt tolerance by reducing stomatal aperture and improving water retention, which contributes to better water status, scavenging ROS, and alleviating leaf wilting under stress. In conclusion, this study highlights the dual role of galactose transporters VfSWEET19 and VfSWEET26 in attenuating plant immunity while enhancing drought and salt tolerance, offering valuable candidate genes for resistance breeding.