GAI1 underlines the antagonism between gibberellin and jasmonic acid in modulating disease resistance

Cassava bacterial blight (CBB) is a devastating disease affecting cassava production worldwide. Although phytohormones are important in regulating defense responses, their roles and the possible crosstalk in cassava remain elusive. Here, we illustrate the antagonistic effects of gibberellin (GA) and jasmonic acid (JA) in modulating disease resistance to CBB. Notably, we found that GIBBERELLIN INSENSITIVE1 (GAI1), a critical repressor of GA signaling, physically interacted with JASMONATE ZIM DOMAIN2.2 (JAZ2.2). JAZ2.2 negatively regulates cassava disease resistance by interfering with JA signaling through its direct interaction with MYELOCYTOMATOSIS2.2 (MYC2.2), thereby inhibiting the transcription of several resistant genes, including MeSERK1, MeLYK3, MeZAR1, MeADR2, MePR1, MePR4.1, MePR5. Interestingly, the interaction between GAI1 and JAZ2.2 releases the MYC2.2 and then activates the transcription of downstream resistant genes, resulting the antagonistic effects of GA and JA. In summary, this study clarifies the antagonism between GA and JA in modulating cassava disease resistance, which is underlined by the interaction between GAI1 and JAZ2.2. The GAI1-JAZ2.2-MYC2.2 gene network not only extends the our understanding of the phytohormone signaling pathway, but also provides new clues for the genetic improvement of cassava disease resistance.