SlASR3 mediates crosstalk between auxin and jasmonic acid signaling to regulate trichome formation in tomato

Trichomes play a pivotal role in plant resistance to biotic and abiotic stresses. Both auxin and jasmonic acid (JA) could induce tomato type II, V, and VI trichome formation. However, the existence of crosstalk between auxin and JA in trichome formation is not yet fully elucidated. In this study, we identified a Trihelix/MYB-like gene, SlASR3, is inhibited by both auxin and JA and is expressed in type II and VI trichomes in tomatoes. Knock-down or knockout of SlASR3 increased the densities of type II and VI trichomes, whereas overexpression of SlASR3 reduced the densities of type II and VI trichomes. SlASR3 was involved in the indole acetic acid (IAA)- and JA-induced formation of these trichome types. SlARF4 negatively regulated the transcription of SlASR3, and its effect on IAA-induced trichome formation depended on SlASR3. Likewise, SlMYC1 negatively regulated the transcription of SlASR3, and the regulation of SlMYC1 on JA-induced trichome formation was also SlASR3-dependent. Knock-down or knockout of SlASR3 increased the resistance to two-spotted spider mites in tomatoes. The research findings demonstrate that SlASR3 acts as a mediator in the crosstalk between JA and auxin signaling to regulate trichome formation and provide a new candidate gene for enhancing resistance to two-spotted spider mites.