title: Constitutive expression of two apple (Malus x domestica Borkh.) homolog genes of LIKE HETEROCHROMATIN PROTEIN1 affects flowering time and whole-plant growth in transgenic Arabidopsis.
abstract: Fruit trees, such as apple (Malus x domestica Borkh.), are woody perennial plants with a long juvenile phase. The biological analysis for the regulation of flowering time provides insights into the reduction of juvenile phase and the acceleration of breeding in fruit trees. In Arabidopsis, LIKE HETEROCHROMATIN PROTEIN1 (LHP1) is involved in epigenetic silencing of the target genes such as flowering genes. We isolated and characterized twin apple LHP1 homolog genes, MdLHP1a and MdLHP1b. These genes may have been generated as a result of ancient genome duplication. Although the putative MdLHP1 proteins showed lower similarity to any other known plant LHP1 homologs, a chromo domain, a chromo shadow domain, and the nuclear localization signal motifs were highly conserved among them. RT-PCR analysis showed that MdLHP1a and MdLHP1b were expressed constantly in developing shoot apices of apple trees throughout the growing season. Constitutive expression of MdLHP1a or MdLHP1b could compensate for the pleiotropic phenotype of lhp1/tfl2 mutant, suggesting that apple LHP1 homolog genes are involved in the regulation of flowering time and whole-plant growth. Based on these results, LHP1 homolog genes might have rapidly evolved among plant species, but the protein functions were conserved, at least between Arabidopsis and apple.
authors.affiliation: Apple Breeding and Physiology Research Team, National Institute of Fruit Tree Science, 92-24 Shimo-kuriyagawa, Morioka, Iwate 020-0123, Japan.
authors.forename: Naozumi
authors.initials: N
authors.lastname: Mimida
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Kidou
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kotoda
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D001483:Base Sequence; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D035264:Flowers / Q000235:genetics / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D027845:Malus / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D017931:DNA Primers; D018076:DNA, Complementary; D018744:DNA, Plant; D010940:Plant Proteins; C443901:like heterochromatin protein 1