YTH Domain Proteins Play an Essential Role in Rice Growth and Stress Response

As the most prevalent epi-transcriptional modification, m⁶A modifications play essential roles in regulating RNA fate. The molecular functions of YTH521-B homology (YTH) domain proteins, the most known READER proteins of m⁶A modifications, have been well-studied in animals. Although plants contain more YTH domain proteins than other eukaryotes, little is known about their biological importance. In dicot species Arabidopsis thaliana, the YTHDFA clade members ECT2/3/4 and CPSF30-L are well-studied and important for cell proliferation, plant organogenesis, and nitrate transport. More emphasis is needed on the biological functions of plant YTH proteins, especially monocot YTHs. Here we presented a detailed phylogenetic relationship of eukaryotic YTH proteins and clustered plant YTHDFC clade into three subclades. To determine the importance of monocot YTH proteins, YTH knockout mutants and RNAi-induced knockdown plants were constructed and used for phenotyping, transcriptomic analysis, and stress treatments. Knocking out or knocking down OsYTHs led to the downregulation of multicellular organismal regulation genes and resulted in growth defects. In addition, loss-of-function ythdfa mutants led to better salinity tolerance whereas ythdfc mutants were more sensitive to abiotic stress. Overall, our study establishes the functional relevance of rice YTH genes in plant growth regulation and stress response.