How Ethylene Reddens Apples

Ethylene is essential for the ripening of climacteric fruits, and a rapid burst of ethylene production and a rise in respiration occur at the transition to ripening.  In ripening apple (Malus domestica) fruits, the accumulation of anthocyanins that is responsible for reddening is correlated with ethylene release but how precisely are the two processes related? An et al. (10.1104/pp.18.00068) report that ethylene markedly induces the expression of MdMYB1, a positive regulator of anthocyanin biosynthesis, in apple fruits. In addition, they found that Ethylene Insensitive 3-like protein (MdEIL1), a transcription factor that binds directly to the promoter of MdMYB1 and transcriptionally activates its expression, plays a role in controlling anthocyanin biosynthesis and fruit coloration. Furthermore, MdMYB1 interacted with the promoter of ETHYLENE RESPONSE FACTOR3 (MdERF3), a key regulator of ethylene biosynthesis, thereby providing a positive feedback for ethylene biosynthesis regulation. These the ethylene signal interacts with the MdMYB transcription factor to regulate ethylene biosynthesis and fruit coloration in apple.