MdDSK2a-Like-MdMTA Module Functions in Apple Cold Response via Regulating ROS Detoxification and Cell Wall Deposition

N⁶-methyladenosine (m⁶A) is the most abundant internal RNA modification in eukaryotic cells. Although the importance of its roles in mRNA metabolism, plant development, and stress responses has been well documented, regulation of its machinery is largely unknown in plants. Here, it is reported that MdMTA positively regulates cold tolerance. Combining MeRIP-seq and RNA-seq, it is found that MdMTA regulates the m⁶A and expression levels of cold-responsive genes under cold stress, including those involved in reactive oxygen species (ROS) detoxification and cell wall deposition. Further analysis reveals that MdMTA promotes ROS scavenging and the deposition of cellulose and hemicellulose by regulating the mRNA stability of the relevant genes under cold conditions. MdDSK2a-like, a ubiquitin receptor protein, mediates MdMTA degradation by the 26S ubiquitin-dependent proteasome and autophagy pathways. MdDSK2a-like negatively regulates cold tolerance by reducing the m⁶A levels of MdMTA target genes. Consistently, MdDSK2a-like inhibits ROS scavenging and the deposition of cellulose and hemicellulose under cold conditions. Genetic dissection shows that MdDSK2a-like acts upstream of MdMTA in cold response. The results not only reveal the degradation of MdMTA, but also illustrate the molecular mechanism of the MdDSK2a-like-MdMTA module in m⁶A modification and cold response.