Abstract

In climacteric fruits, ripening is triggered by a shift from auto-inhibitory to auto-catalytic ethylene production, but the activation of system II autocatalytic burst remains unclear. Here, we identified two MADS-box transcription factors, PpMADS2 and PpMADS4, as key positive regulators in peach ( Prunus persica L. Batsch) ripening. Their expression increased during maturation and was induced by ethylene. Overexpression in pre-ripening fruit accelerated ethylene production, colour change, sugar accumulation and softening, while silencing delayed these processes. PpMADS2 interacts with PpMADS4 to form a functional complex which potentiates their activity, and they act by directly binding to and activating the promoters of ethylene biosynthetic genes PpACS1 and PpACO1 , thereby promoting peach ethylene biosynthesis. Conversely, synthesis of ethylene in turn promotes the expression of PpMADS2/4 for positive feedback, amplifying ethylene production, contributing to the system II autocatalytic burst, ultimately leading to the maturation of peach fruit. This study provides a new insight into the MADS-box-ethylene regulatory network controlling climacteric fruit ripening.