Tomato SlYTH1 encoding a putative RNA mA reader affects plant growth and fruit shape.

N-methyladenosine (mA), the most abundant and common modification on eukaryotic mRNA, plays crucial roles in multiple biological processes through controlling endogenous gene activity in organisms. The mA reader specifically recognizes the mA mark to mediate the regulation of mA on mRNA, and determines the fate of its target mRNA. In plants, the currently confirmed mA readers are YTH (YT521B homology) domain-containing proteins. We previously reported that tomato contains 9 YTH genes, of which SlYTH1 has the strongest expression. The present study reports the functional characterization of SlYTH1 in tomato. SlYTH1 mutants generated via CRISPR/Cas9 technology exhibited pleiotropic phenotypes, including low seed germination rate, shortened seedling root, retarded plant growth and development during vegetative development, and elongated and longitudinally flattened fruit with reduced the locule number. SlYTH1 knockout reduced GA content and downregulated the expression of related genes in gibberellin biosynthesis pathway. Moreover, exogenous GA application could partially restore the phenotypic defects caused by SlYTH1 mutations. SlYTH1 knockout could alleviate the inhibition of seedling root elongation by exogenous GA application at relatively low concentration. These facts indicated SlYTH1 is involved in regulating gibberellin biosynthesis and plays important roles in multiple physiological processes in tomato.