TACO LEAF, a putative transcriptional regulator in Arabidopsis, is a target of the protein kinase CK2

During the growth of multicellular organisms, spatial and temporal patterns of gene expression are strictly regulated to ensure that developmental programs are invoked at the appropriate stage. In this work, we describe a putative transcriptional regulator in Arabidopsis, TACO LEAF (TCO), whose overexpression results in the ectopic activation of reproductive genes during vegetative growth. Isolated as an activation-tagged allele, tco-1D displays gene misexpression patterns and phenotypic abnormalities, such as curled leaves and early flowering, that resemble chromatin regulatory mutants. A role for TCO in this mode of transcriptional regulation is further supported by the subnuclear accumulation patterns of TCO protein and the genetic interactions between tco-1D and mutants of chromatin modifiers. The endogenous expression pattern of TCO and the gene misregulation displayed by tco loss-of-function mutants suggest that this factor is involved in seed development. We also demonstrate that specific serine residues of TCO protein are targeted by the ubiquitous kinase CK2. Collectively, these results identify TCO as a novel regulator of gene expression whose activity is likely influenced by phosphorylation, as is the case with many chromatin regulators