Plant growth and development are controlled by a delicate balance of hormonal cues. Growth-promoting hormones and growth-inhibiting counterparts often antagonize each other in their action, but the molecular mechanisms underlying these events remain largely unknown. Here, we report a cross-talk mechanism that enables a receptor-like kinase, FERONIA (FER), a positive regulator of auxin-promoted growth, to suppress the abscisic acid (ABA) response through activation of ABI2, a negative regulator of ABA signaling. The FER pathway consists of a FER kinase interacting with guanine exchange factors GEF1, GEF4, and GEF10 that, in turn, activate GTPase ROP11/ARAC10. Arabidopsis mutants disrupted in any step of the FER pathway, including fer, gef1gef4gef10, or rop11/arac10, all displayed an ABA-hypersensitive response, implicating the FER pathway in the suppression mechanism. In search of the target for the FER pathway, we found that the ROP11/ARAC10 protein physically interacted with the ABI2 phosphatase and enhanced its activity, thereby linking the FER pathway with the inhibition of ABA signaling.
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