The m6A Reader MhYTP2 Regulates MdERF54 mRNA Stability and Contributes to Hypoxia Tolerance in Apple (Malus domestica).

Hypoxia is one of the main challenges in apple (Malus domestica) cultivation. However, breeding hypoxia-tolerant cultivars demands a thorough understanding of the responses of apple trees to low oxygen supply. Studies have indicated that N6-methyladenosine (m6A) reader regulates plant stress response by binding to their corresponding mRNA targets with m6A modification. The present study investigated the function and mechanism of apple m6A reader MhYTP2 under hypoxia stress. Here, we found that the overexpression of MhYTP2 improved hypoxia resistance in apple. Previous RNA immunoprecipitation sequencing (RIP-seq) results identified the mRNA of Ethylene Response Factor 54 (ERF54) as a direct target of MhYTP2; electronic mobility shift assays (EMSA) further verified this finding. Further transcription inhibition assays demonstrated that MhYTP2 increased MdERF54 mRNA stability. Under hypoxia stress, MdERF54 increased the activities of pyruvate decarboxylase (PDC), lactate dehydrogenase (LDH), and alcohol dehydrogenase (ADH) the key enzymes in anaerobic respiration pathway, activated the ethylene signalling pathway, increased the chlorophyll content of plant leaves and photosynthetic rates, enhanced the adaptability of roots, reduced the damage to biofilm and antioxidant system, and enhanced the antioxidant capacity. Thus, our results elucidated the molecular mechanisms by which the MhYTP2-MdERF54 module influences the response of the apple to hypoxia stress.