title: Dissection of two major components of the post-zygotic hybridization barrier in rice endosperm.
abstract: A post-zygotic hybridization barrier is often observed in the endosperm of seeds produced by interspecific or interploidy crosses. In Arabidopsis thaliana, for example, hybrid endosperm from both types of cross shows altered timing of cellularization and an altered rate of nuclear divisions. Therefore, it has been proposed that interspecific and interploidy crosses share common molecular mechanisms for establishment of an effective species barrier. However, these two types of hybridization barrier may be initiated by different intrinsic cues: the interspecific cross barrier arises after hybridization of genomes with differences in DNA sequences, while the interploidy cross barrier arises after hybridization of genomes with the same DNA sequences but differences in ploidy levels. In this study, we performed interploidy crosses to identify components of the post-hybridization barrier in the endosperm of rice. We performed an intra-cultivar cross of autotetraploid (4n) × diploid (2n) rice, and found precocious cellularization and a decreased rate of nuclear division in the syncytial endosperm. By contrast, seeds from the reciprocal cross showed delayed cellularization and an increased rate of nuclear division. This differential effect on nuclear division rates contrasts with the outcome of rice interspecific crosses, which were previously shown to have altered timing of cellularization without any change in nuclear division rates. Thus, we propose that the post-zygotic hybridization barrier in rice endosperm has two separable components, namely control of the timing of cellularization and control of the nuclear division rates in the syncytial stage of endosperm development.
authors.affiliation: Graduate School of Biological Science, Nara Institute of Science and Technology, Nara, 630-0192, Japan; Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, 920-1192, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sekine
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Furuumi
authors.forename: Akemi
authors.initials: A
authors.lastname: Ono
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yamada
authors.forename: Nori
authors.initials: N
authors.lastname: Kurata
authors.forename: Tetsu
authors.initials: T
authors.lastname: Kinoshita
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D048750:Cell Nucleus Division; D003433:Crosses, Genetic; D056625:Endosperm / Q000235:genetics*; D006824:Hybridization, Genetic; D012275:Oryza / Q000235:genetics* / Q000502:physiology; D011003:Ploidies; D012639:Seeds / Q000502:physiology
keywords: Oryza sativa; cell cycle; endosperm; genomic imprinting; hybridization barrier; interploidy cross