TET 3‐ mediated demethylation in tomato activates expression of a CETS gene that stimulates vegetative growth

Expression of the mammalian DNA demethylase enzyme TET 3 in plants can be used to induce hypomethylation of DNA . In tomato lines that express a TET 3 transgene, we observed distinct phenotypes including an increase in the length and number of leaves of primary shoots. As these changes resemble phenotypes observed in plants with strong expression of SELF PRUNING ( SP ), a member of the PEBP / CETS family, we investigated in TET 3 lines the expression levels of members of the PEBP / CETS gene family, which affect shoot architecture and growth of sympodial units in tomato. We did not detect any changes in SP expression in TET 3 lines, but for CEN 1.1 , a putative family member that has not been functionally characterized, we identified changes in gene expression that corresponded to hypomethylation in the upstream region. In tomato wild type, CEN 1.1 is expressed in roots, petals, and shoot apices but not in mature leaves. In contrast, in TET 3 transformants, the CEN 1.1 gene became hypomethylated and activated in leaves. Ectopic expression of CEN 1.1 in tomato caused similar phenotypes to those seen in TET 3 transformants. Vegetative growth was increased, resulting both in a delay in inflorescence development and in an instability of the inflorescences, which frequently reverted to a vegetative state. Ectopic expression of CEN 1.1 in Arabidopsis thaliana also caused floral repression. Our data suggest that the phenotypes observed in TET 3 lines are a consequence of ectopic activation of CEN 1.1, which promotes vegetative growth, and that CEN 1.1 expression is sensitive to DNA methylation changes.