The SlHY5‐SlbZIP17/SlMYC2‐ <i>SlβCA3</i> Module Regulates Tomato Defence Against <i>Pst</i> DC3000 Under Low Light Stress

Low light stress can aggravate the occurrence of plant bacterial diseases. However, how the basic leucine zipper (bZIP) family regulates the synergistic regulatory network induced by low light stress and pathogen infection at the transcriptional level is still unclear. In this study, we identified SlbZIP17, which has a dual response to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) and low light conditions. It revealed that SlbZIP17 reduces tomato (Solanum lycopersicum) disease symptoms by activating the positive regulator gene SlβCA3 of Pst DC3000 and increasing the ability of plants to scavenge reactive oxygen species (ROS). Further studies revealed that SlbZIP17 forms a heterodimer with SlMYC2 to synergistically amplify the transcriptional activation effect on SlβCA3. Moreover, under low light stress, SlHY5 was inhibited, which directly reduced SlbZIP17 and SlβCA3 expression. This process led to a decrease in the interaction of SlbZIP17 and SlMYC2, which reduced the ability of the transcription complex to activate SlβCA3 and thereby increasing the severity of disease symptoms induced by Pst DC3000. These findings offer insights into the mechanism underlying the low light stress-pathogen interaction and provide new targets for improving resistance in tomato varieties for facility cultivation agriculture.