H2O2-activated transcription factor MdERF4 negatively regulates ethylene biosynthetic during fruit ripening by suppressing MdACS1 transcription

Ethylene is essential for the ripening of climacteric fruit. The accumulation of reactive oxygen species (ROS) in apples can accelerate fruit ripening. Although ethylene signaling has been extensively studied, the transcriptional regulation of ethylene biosynthesis combined with ROS signaling remains limited. Hydrogen peroxide (H2O2) is one of the most abundant ROS involved in fruit development, ripening and senescence. Therefore, we treated apple fruit with different concentrations of H2O2 and found that low concentrations of H2O2 stimulated the activities of antioxidant enzymes, improved the scavenging ability of ROS, and reduced ethylene production·H2O2, as a signaling molecule, activated the expression of MdERF4, which can directly bind to proMdACS1 and suppress its expression, thereby inhibiting ethylene synthesis. Moreover, H2O2 indirectly attenuated the expression of MdACS1 and reduced ethylene production, thereby prolonging the storage period of the fruit by indirectly promoting the inhibitory effect of the ethylene inhibitor MdERF4 on proMdERF3. Our findings provide insights into the transcriptional regulation of ethylene biosynthesis during fruit ripening.