The ABI3-ERF1 module mediates ABA-auxin crosstalk to regulate lateral root emergence

Summary

Lateral root (LR) development is regulated by hormones and environmental signals. Abscisic acid (ABA) is involved in LR development, but it is not well understood how ABA signaling interacts with auxin to regulate LR formation. Here, we report that Arabidopsis ERF1 is responsive to ABA during LR development and mediates the crosstalk between ABA and auxin signaling to regulate LR emergence. ABA attenuates ERF1-mediated excessive auxin accumulation with altered distribution known to inhibit LR emergence. ABI3 acts as a negative factor in LR emergence and transcriptionally activates ERF1 by binding to the RY motif in its promoter, and reciprocally, ERF1 activates ABI3, which forms a positive regulatory loop that enables rapid signal amplification. Notably, ABI3 physically interacts with ERF1, consequently reducing the cis element-binding activities of both ERF1 and ABI3 and thus attenuating ERF1-regulated transcription of PIN1, AUX1, and ARF7 involved in the modulation of LR emergence and ABI3-regulated ABI5 in ABA signaling, which may provide a molecular rheostat to avoid overamplification of auxin and ABA signaling. Taken together, our findings unveil the pivotal ABI3-ERF1 module that mediates the crosstalk between ABA and auxin signaling in LR emergence.