title: Characterization of genomic sequence showing strong association with polyembryony among diverse Citrus species and cultivars, and its synteny with Vitis and Populus.
abstract: Polyembryony, in which multiple somatic nucellar cell-derived embryos develop in addition to the zygotic embryo in a seed, is common in the genus Citrus. Previous genetic studies indicated polyembryony is mainly determined by a single locus, but the underlying molecular mechanism is still unclear. As a step towards identification and characterization of the gene or genes responsible for nucellar embryogenesis in Citrus, haplotype-specific physical maps around the polyembryony locus were constructed. By sequencing three BAC clones aligned on the polyembryony haplotype, a single contiguous draft sequence consisting of 380 kb containing 70 predicted open reading frames (ORFs) was reconstructed. Single nucleotide polymorphism genotypes detected in the sequenced genomic region showed strong association with embryo type in Citrus, indicating a common polyembryony locus is shared among widely diverse Citrus cultivars and species. The arrangement of the predicted ORFs in the characterized genomic region showed high collinearity to the genomic sequence of chromosome 4 of Vitis vinifera and linkage group VI of Populus trichocarpa, suggesting that the syntenic relationship among these species is conserved even though V. vinifera and P. trichocarpa are non-apomictic species. This is the first study to characterize in detail the genomic structure of an apomixis locus determining adventitious embryony.
authors.affiliation: Department of Citrus Research, National Institute of Fruit Tree Science, Shizuoka 424-0292, Japan.
authors.forename: Michiharu
authors.initials: M
authors.lastname: Nakano
authors.forename: Takehiko
authors.initials: T
authors.lastname: Shimada
authors.forename: Tomoko
authors.initials: T
authors.lastname: Endo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujii
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Nesumi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kita
authors.forename: Masumi
authors.initials: M
authors.lastname: Ebina
authors.forename: Tokurou
authors.initials: T
authors.lastname: Shimizu
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Omura
mesh_terms: D060832:Apomixis / Q000235:genetics*; D001483:Base Sequence; D022202:Chromosomes, Artificial, Bacterial; D002957:Citrus / Q000196:embryology / Q000235:genetics*; D018744:DNA, Plant / Q000032:analysis; D018745:Genome, Plant; D023281:Genomics; D006239:Haplotypes; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D020641:Polymorphism, Single Nucleotide; D032107:Populus / Q000235:genetics*; D012639:Seeds / Q000196:embryology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D026801:Synteny; D027843:Vitis / Q000235:genetics*
chemical_list: D018744:DNA, Plant