AcERF1B and AcERF073 Positively Regulate Indole-3-acetic Acid Degradation by Activating <i>AcGH3.1</i> Transcription during Postharvest Kiwifruit Ripening

Abstract

Ethylene can accelerate the postharvest ripening process of kiwifruit, while indole-3-acetic acid (IAA) delays it. However, the molecular mechanism by which ethylene regulates IAA degradation is unclear. Here, we found that ethephon promotes the degradation of free IAA in kiwifruit. Furthermore, ethylene can promote the expression of <i>AcGH3.1</i> and enhance its promoter activity. Two ethylene response factors (ERFs), AcERF1B and AcERF073, were obtained using an <i>AcGH3.1</i> promoter as bait for a yeast one-hybrid screening library. Both AcERF1B and AcERF073 bind to the <i>AcGH3.1</i> promoter to activate it. Also, AcERF1B/073 enhanced <i>AcGH3.1</i> expression, decreased the free IAA content, and increased the IAA-Asp content in kiwifruit. In addition, we found that the AcERF1B and AcERF073 proteins directly interact, and this interaction enhanced their binding to the <i>AcGH3.1</i> promoter. In summary, our results suggest that AcERF1B and AcERF073 positively regulate IAA degradation by activating <i>AcGH3.1</i> transcription, which accelerated postharvest kiwifruit ripening.