MHZ3: a key regulator of ethylene signaling in rice

The plant hormone ethylene regulates plant growth, development, and stress responses. Recent studies on early signaling events following ethylene perception in rice (Oryza sativa) have identified MAO HU ZI 3 (MHZ3) as a stabilizer of the ethylene receptors ETHYLENE RESPONSE SENSOR 2 (OsERS2) and ETHYLENE RECEPTOR 2 (OsETR2). MHZ3 ensures the interaction of these receptors with CONSTITUTIVE TRIPLE RESPONSE 2 (OsCTR2), thereby maintaining OsCTR2 activity. Ethylene treatment disrupts the interactions within the MHZ3/receptors/OsCTR2 protein complex, leading to decreased OsCTR2 phosphorylation and the initiation of downstream signaling. Recent studies have established MHZ3 as the primary regulator and switch for OsCTR2 phosphorylation. In this review, we explore the role of MHZ3 in regulating ethylene signaling and highlight its effects on plant growth, development, and stress responses at the plant holobiont level.