Abstract
Expression of the mammalian DNA demethylase enzyme TET3 in plants can be used to induce hypomethylation of DNA. In tomato lines that express a TET3 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 TET3 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 TET3 lines, but for CEN1.1, 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, CEN1.1 is expressed in roots, petals, and shoot apices but not in mature leaves. In contrast, in TET3 transformants, the CEN1.1 gene became hypomethylated and activated in leaves. Ectopic expression of CEN1.1 in tomato caused similar phenotypes to those seen in TET3 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 CEN1.1 in Arabidopsis thaliana also caused floral repression. Our data suggest that the phenotypes observed in TET3 lines are a consequence of ectopic activation of CEN1.1, which promotes vegetative growth, and that CEN1.1 expression is sensitive to DNA methylation changes.
Highlights
Statement: This study demonstrates the value of the mammalian demethylase TET3 as a tool to induce genes that are sensitive to DNA hypomethylation, while providing new information on the process of shoot architecture determination in tomato.Organization of shoot architecture in flowering plants is extremely important for the normal development of the plant, both under usual environmental conditions and when the plant is under stress
Upward growth of the shoot is again continued from the most proximal axillary bud of the previous sympodial unit in an indeterminate fashion (Lifschitz et al, 2006). The establishment of this pattern relies on the balance between the expression levels of genes in the tomato PEBP gene family, called the CETS (CENTRORADIALIS/TERMINAL FLOWER 1/SELF PRUNING) gene family after its founding members (Shalit et al, 2009)
Among the plants that we had selected on the basis that they contained the 35S::CEN1.1 construct, we identified three plants that no longer expressed the transgene
Summary
Significance Statement: This study demonstrates the value of the mammalian demethylase TET3 as a tool to induce genes that are sensitive to DNA hypomethylation, while providing new information on the process of shoot architecture determination in tomato. Upward growth of the shoot is again continued from the most proximal axillary bud of the previous sympodial unit in an indeterminate fashion (Lifschitz et al, 2006) The establishment of this pattern relies on the balance between the expression levels of genes in the tomato PEBP gene family (phosphatidylethanolamine-binding protein), called the CETS (CENTRORADIALIS/TERMINAL FLOWER 1/SELF PRUNING) gene family after its founding members (Shalit et al, 2009). Overexpression of the SFT gene causes early flowering, the opposite phenotype to overexpressing SP, which results in delayed termination of the primary shoot and increased numbers of leaves per sympodial unit (Lifschitz et al, 2006; McGarry & Ayre, 2012; Pnueli et al, 1998). Ectopic expression of CEN1.1 in Arabidopsis thaliana results in an increase in the number of rosette leaves and a delay in flowering
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