A LIM-domain protein from sunflower is localized to the cytoplasm and/or nucleus in a wide variety of tissues and is associated with the phragmoplastin dividing cells

LIM proteins are important eucaryotic developmental regulators characterize d by the presence of one or several double zinc finger motifs, the LIM doma ins, which are protein-interacting domains. Using the cDNA of the previousl y described pollen LIM protein PLIM1 from sunflower as a hybridization prob e we have isolated the coding sequence for a related protein from cDNA libr aries from various sunflower organs. This protein, WLIM1, is 188 amino acid s long and, like the pollen protein PLIM1, contains two LIM domains, separa ted by a 48 residue spacer region. The two sunflower proteins are structura lly related to the animal LIM proteins CRP and MLP. A WLIM1 gene transcript was detected by RT-PCR in all vegetative and reproductive plant organs tes ted. Polyclonal antibodies raised against the bacterially expressed and aff inity-purified protein recognize a polypeptide of ca. 50 kDa in these organ s. Immunocytochemical studies detect the protein in many cell types in each of these organs where it is localized either to the cytoplasm, the nucleus , or both. The protein is often associated with plastids and smaller cellul ar structures or organelles. In late anaphase and early telophase of dividi ng cells from ovaries, stems and roots it accumulates in the phragmoplast, and may therefore also play a role in cytokinesis.