title: Evolutionary conservation of TORC1 components, TOR, Raptor, and LST8, between rice and yeast.
abstract: Target of rapamycin (TOR) is a conserved eukaryotic serine/threonine kinase that functions as a central controller of cell growth. TOR protein is structurally defined by the presence several conserved domains such as the HEAT repeat, focal adhesion target (FAT), FKBP12/rapamycin binding (FRB), kinase, and FATC domains starting from the N-terminus. In most eukaryotes, TOR forms two distinct physical and functional complexes, which are termed as TOR complex 1 (TORC1) and TORC2. However, plants contain only TORC1 components, i.e., TOR, Raptor, and LST8. In this study, we analyzed the gene structure and functions of TORC components in rice to understand the properties of the TOR complex in plants. Comparison of the locations of introns in these genes among rice and other eukaryotes showed that they were well conserved among plants except for Chlamydomonas. Moreover, the intron positions in the coding sequence of human Raptor and LST8 were closer to those of plants than of fly or nematode. Complementation tests of rice TOR (OsTOR) components in yeast showed that although OsTOR did not complement yeast tor mutants, chimeric TOR, which consisted of the HEAT repeat and FAT domain from yeast and other regions from rice, rescued the tor mutants, indicating that the HEAT repeat and FAT domains are important for species-specific signaling. OsRaptor perfectly complemented a kog1 (yeast Raptor homolog) mutant, and OsLST8 partially complemented an lst8 mutant. Together, these data suggest the importance of the N-terminal region of the TOR, HEAT, and FAT domains for functional diversification of the TOR complex.
authors.affiliation: Department of Biology, Shizuoka University, 836 Ohya Suruga-ku, Shizuoka, 422-8529, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Maegawa
authors.affiliation: Department of Biology, Shizuoka University, 836 Ohya Suruga-ku, Shizuoka, 422-8529, Japan.
authors.forename: Rumi
authors.initials: R
authors.lastname: Takii
authors.affiliation: Department of Biology, Shizuoka University, 836 Ohya Suruga-ku, Shizuoka, 422-8529, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ushimaru
authors.affiliation: Department of Biology, Shizuoka University, 836 Ohya Suruga-ku, Shizuoka, 422-8529, Japan. sakozak@ipc.shizuoka.ac.jp.
authors.forename: Akiko
authors.initials: A
authors.lastname: Kozaki
mesh_terms: D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D005800:Genes, Fungal; D017343:Genes, Plant; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000235:genetics*; D012275:Oryza / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D046912:Multiprotein Complexes; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases
keywords: LST8; Raptor; Rice; Saccharomyces cerevisiae; TORC1; Target of rapamycin