A single homeobox gene triggers phase transition, embryogenesis and asexual reproduction
A single homeobox gene triggers phase transition, embryogenesis and asexual reproduction
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DOI：
10.1038/nplants.2015.209
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发表时间：
2016-02-01
期刊：
影响因子：
18
通讯作者：
Reski, Ralf
中科院分区：
文献类型：
--
作者：
Horst, Nelly A.;Katz, Aviva;Reski, Ralf
植物在单倍体配子体和二倍体孢子体阶段之间交替。减数分裂和受精分别启动了这两种不同的个体发育(1)。在营养孢子体组织上触发异位胚胎发育的基因被很好地描述(2，3)；然而，从配子体组织中控制胚胎发育的遗传控制仍然是难以捉摸的。在这里，我们在苔藓Physcomitrella patens中证明了异位过表达同源盒基因BELL1可以诱导胚胎形成，并随后在没有受精的情况下从特定的配子体细胞繁殖二倍体孢子体。与此相一致的是，BELL1功能缺失突变体具有野生型表型，只是它们的卵细胞更大，不能形成胚胎。我们的研究结果表明，BELL1是一种主控调控因子，参与了P.patens配子体到孢子体的转化过程，并为多细胞二倍体孢子体胚胎的进化提供了机械性的见解。这一发展创新促进了约5亿年前植物对土地的殖民(4)，从而塑造了我们目前的生态系统。
Plants characteristically alternate between haploid gametophytic and diploid sporophytic stages. Meiosis and fertilization respectively initiate these two different ontogenies(1). Genes triggering ectopic embryo development on vegetative sporophytic tissues are well described(2,3); however, a genetic control of embryo development from gametophytic tissues remains elusive. Here, in the moss Physcomitrella patens we show that ectopic overexpression of the homeobox gene BELL1 induces embryo formation and subsequently reproductive diploid sporophytes from specific gametophytic cells without fertilization. In line with this, BELL1 loss-of-function mutants have a wild-type phenotype, except that their egg cells are bigger and unable to form embryos. Our results identify BELL1 as a master regulator for the gametophyte-to-sporophyte transition in P. patens and provide mechanistic insights into the evolution of embryos that can generate multicellular diploid sporophytes. This developmental innovation facilitated the colonization of land by plants about 500 million years ago(4) and thus shaped our current ecosystems.