MADS-Box Transcription Factors PpMADS2 and PpMADS4 Are Crucial Regulators in Climacteric Peach (Prunus persica L....

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.