Identification of proteins that interact with a TcMago-TcY14 heterodimer complex in Taiwania crytomerioides.

The Mago-Y14 heterodimer, which is highly conserved among eukaryotes, is the core component of the exon-exon junction complex (EJC) and regulates oogenesis, embryogenesis and germ-line sex determination in Drosophila and the nematode Caenorhabditis elegans. To further survey these proteins in plants and to identify plant developmental processes with which the Mago-Y14 heterodimer is associated, we used the TcMago-TcY14 heterodimer as the bait protein in a yeast two-hybrid screen and searched for its binding partners in a cDNA library from a 3-year-old Taiwania (Taiwania cryptomerioides Hayata) seedling. We found three clones, an unknown protein (Tc61), a pectin methylesterase-like protein (Tc62) and a TPR (tetratricopeptide repeat)-like protein (Tc72). The Tc61 protein interacted strongly with the TcMago-TcY14 heterodimer, and its transcript was expressed in stems and leaves of 3-year-old Taiwania seedlings and in microsporangiate and ovulate cones. The pectin methylesterase-like protein was expressed abundantly in the roots of 3-year-old Taiwania seedlings and in pollinated ovulate cones, indicating that binding with the TcMago-TcY14 heterodimer may be involved in root development and growth of pollen tubes during pollination. The Tc72 protein encoded a complete TPR-like protein that is highly conserved among plants, with 10 alpha-helices and three conserved TPR motifs containing five consensus residues necessary for stable inter-helix packing. A tissue expression assay and light/dark treatments showed that the Tc72 gene was expressed abundantly in the leaves of seedlings and was sensitive to light and dark, as are the Tcmago and TcY14 genes, implying that the TcMago-TcY14 heterodimer interaction with Tc72 may be related to chloroplast protein transport.