title: Impact of segmental chromosomal duplications on leaf size in the grandifolia-D mutants of Arabidopsis thaliana.
abstract: The number of cells in an organ is a major factor that specifies its size. However, the genetic basis of cell number determination is not well understood. To obtain insight into this genetic basis, three grandifolia-D (gra-D) mutants of Arabidopsis thaliana were characterized that developed huge leaves with two to three times more cells than the wild-type. Genetic and microarray analyses showed that a large segmental duplication had occurred in all the gra-D mutants, consisting of the lower part of chromosome 4. In the duplications, genes were found that encode AINTEGUMENTA (ANT), a factor that extends the duration of cell proliferation, and CYCD3;1, a G(1)/S cyclin. The expression levels of both genes increased and the duration of cell proliferation in the leaf primordia was extended in the gra-D mutants. Data obtained by RNAi-mediated knockdown of ANT expression suggested that ANT contributed to the huge-leaf phenotype, but that it was not the sole factor. Introduction of an extra genomic copy of CYCD3;1 into the wild-type partially mimicked the gra-D phenotype. Furthermore, combined elevated expression of ANT and CYCD3;1 enhanced cell proliferation in a cumulative fashion. These results indicate that the duration of cell proliferation in leaves is determined in part by the interaction of ANT and CYCD3;1, and also demonstrate the potential usefulness of duplication mutants in the elucidation of genetic relationships that are difficult to uncover by standard single-gene mutations or gain-of-function analysis. We also discuss the potential effect of chromosomal duplication on evolution of organ size.
authors.affiliation: Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan. ghori@rikkyo.ac.jp
authors.forename: Gorou
authors.initials: G
authors.lastname: Horiguchi
authors.forename: Nathalie
authors.initials: N
authors.lastname: Gonzalez
authors.forename: Gerrit T S
authors.initials: GT
authors.lastname: Beemster
authors.forename: Dirk
authors.initials: D
authors.lastname: Inzé
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tsukaya
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D018628:Gene Dosage; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011003:Ploidies; D018749:RNA, Plant / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C099055:AINTEGUMENTA protein, Arabidopsis; D029681:Arabidopsis Proteins; C511744:CYCD3;1 protein, Arabidopsis; D016213:Cyclins; D018398:Homeodomain Proteins; D018749:RNA, Plant; D014157:Transcription Factors