杂种偏分离是指杂交后代群体在某个位点的基因型分离比偏离了预期的孟德尔分离比例的一种现象,是来自不同杂交亲本基因之间的不兼容性所致。功能缺失型和功能获得型的基因间互作都可以导致杂种偏分离,其中前者的机理比较简单,即缺陷型的基因组合导致原有功能丧失而造成细胞死亡。功能获得型杂种偏分离系统是由多基因控制的遗传系统,包含两个基本成分：杀手(killer)因子和护卫(protector)因子,此外还有增强子(enhancer)、抑制基因(repressor)等修饰因子。功能获得型杂种偏分离有通用的遗传模型：具有传递优势的单倍型含有高活性的killer+和protector+;传递劣势的单倍型含有低活性的killer-和protector-;中性的单倍型(广亲和型)则含有killer-和protector+。该系统通过killer和protector间的紧密连锁、修饰因子的积累等途径得以在自然选择中保存下来。尽管不同功能获得型杂种偏分离系统的遗传机理有较高的相似性,但分子机制则大相径庭。文章综述了杂种偏分离的遗传和分子机理以及其与杂种不育的关系,以期为后续杂种偏分离研究提供参考。
Segregation distortion (SD) is defined as abnormal segregation ratio of hybrid offsprings at some genetic loci deviating from the Mendelian ratio. SD results from the incompatibility among genes from different parents, which could be due to loss-of-function or gain-of-function gene interactions. The mechanism for loss-of-function SD is relatively simple: defective gene combination leads to loss of the original function and eventual cell death. The gain-of-function hybrid SD system is a multi-gene genetic system, comprising two basic components: the killer and the protector. Additional modifiers, such as enhancers and repressors, are also involved. There is a general genetic model for gain-of-function hybrid SD: haplotypes with transmission advantage possess high-activity killer+ and protector+; those with transmission disadvantage possess low-activity killer- and protector-; neutral haplotypes (wide compatibility types) possess killer- and protector+. Depending upon close linkage between the killer and the protector and the accumulation of modifiers, the SD system survived through natural selection. Although the genetic mechanisms are highly similar, different gain-of-function hybrid SD systems have distinctive molecular mechanisms. In this review, we summarize the genetic and molecular mechanisms of hybrid SD, and the relationship between hybrid SD and hybrid sterility.
[1] Lyttle TW. Segregation distorters. Annu Rev Genet , 1991, 25: 511-557.
[2] Charlesworth B. Driving genes and chromosomes. Nature , 1988, 332(6163): 394-395.
[3] 宋宪亮, 孙学振, 张天真. 偏分离及对植物遗传作图的影响. 农业生物技术学报, 2006, 14(2): 286-292.
[4] Vogl C, Xu SZ. Multipoint mapping of viability and segregation distorting loci using molecular markers. Genetics , 2000, 155(3): 1439-1447.
[5] Kusano A, Staber C, Chan HYE, Ganetzky B. Closing the (Ran)GAP on segregation distortion in Drosophila . BioEssays , 2003, 25(2): 108-115.
[6] Bauer H, Willertbirgit J, Koschorz B. The t complex-encoded GTPase-activating protein Tagap1 acts as a transmission ratio distorter in mice. Nat Genet , 2005, 37(9): 969-973.
[7] Yang JY, Zhao XB, Cheng K, Du HY, Ouyang YD, Chen JJ, Qiu SQ, Huang JY, Jiang YH, Jiang LW, Ding JH, Wang J, Xu CG, Li XH, Zhang QF. A killer-protector system regulates both hybrid sterility and segregation distortion in rice. Science , 2012, 337(6100): 1336-1340.
[8] Burt A, Trivers R. Genes in conflict: the biology of selfish genetic elements. London: Belknap Press, 2006.
[9] Whitkus R. Genetics of adaptive radiation in Hawaiian and Cook Islands species of Tetramolopium (Asteraceae). Ⅱ. Genetic linkage map and its implications for interspecific breeding barriers. Genetics , 1998, 150(3): 1209-1216.
[10] Lin SY, Ikehashi H, Yanagihara S, Kawashima A. Segregation distortion via male gametes in hybrids between Indica and Japonica or wide-compatibility varieties of rice ( Oryza sativa L.). Theor Appl Genet , 1992, 84(7-8): 812-818.
[11] Xu X, Li L, Dong X, Jin W, Melchinger AE, Chen S. Gametophytic and zygotic selection leads to segregation distortion through in vivo induction of a maternal haploid in maize. J Exp Bot., 2013, 64(4): 1083-1096.
[12] Kianian SF, Quiros CF. Generation of a Brassica oleracea composite RFLP map: linkage arrangements among various populations and evolutionary implications. Theor Appl Genet , 1992, 84(5-6): 544-554.
[13] Lyon MF. Transmission ratio distortion in mice. Annu Rev Genet , 2003, 37: 393-408.
[14] Harushima Y, Kurata N, Yano M, Naganmura Y, Sasaki T, Minobe Y, Nakagahra M. Detection of segregation distortions in an indica-japonica rice cross using a high-resolution molecular map. Theor Appl Genet , 1996, 92(2): 145- 150.
[15] Yamagata Y, Yamamoto E, Aya K, Win K, Doi K, Sobrizal, Ito T, Kanamori H, Wu J, Matsumoto T, Matsuoka M, Ashikari M, Yoshimura A. Mitochondrial gene in the nuclear genome induces reproductive barrier in rice. Proc Natl Acad Sci USA , 2010, 107(4): 1494-1499.
[16] Mizuta Y, Harushima Y, Kurata N. Rice pollen hybrid incompatibility caused by reciprocal gene loss of duplicated genes. Proc Natl Acad Sci USA , 2010, 107(47): 20417- 20422.
[17] Flachs P, Mihola O, Šimeček P, Gregorová S, Schimenti JC, Matsui Y, Baudat F, de Massy B, Piálek J, Forejt J, Trachtulec Z. Interallelic and intergenic incompatibilities of the Prdm9 (Hst1 ) gene in mouse hybrid sterility. PLoS Genetics , 2012, 8(11): e1003044.
[18] Long YM, Zhao LF, Niu BX, Su J, Wu H, Chen YL, Zhang QY, Guo JX, Zhuang CX, Mei MT, Xia JX, Wang L, Wu HB, Liu YG. Hybrid male sterility in rice controlled by interaction between divergent alleles of two adjacent genes. Proc Natl Acad Sci USA , 2008, 105(48): 18871-18876.
[19] Pimpinelli S, Dimitri P. Cytogenetic analysis of segregation distortion in Drosophila melanogaster : the cytological organization of the responder ( Rsp ) locus. Genetics , 1989, 121(4): 765-772.
[20] Presgraves DC. Does genetic conflict drive rapid molecular evolution of nuclear transport genes in Drosophila ? BioEssays , 2007, 29(4): 386-391.
[21] Merrill C, Bayraktaroglu L, Kusano A, Ganatzky B. Truncated RanGAP encoded by the Segregation distorter locus of Drosophila . Science , 1999, 283(5408): 1742-1745.
[22] Kusano A, Staber C, Ganetzky B. Nuclear mislocalization of enzymatically active R
