Shirasawa Kenta, Hand Melanie L, Henderson Steven T, Okada Takashi, Johnson Susan D, Taylor Jennifer M, Spriggs Andrew, Siddons Hayley, Hirakawa Hideki, Isobe Sachiko, Tabata Satoshi, Koltunow Anna M G
Kazusa DNA Research Institute, 2-6-7 Kazusa-Kamatari, Kisarazu, Chiba 292-0818, Japan and Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture Flagship, Waite Campus, Hartley Grove, Urrbrae, South Australia 5064, Australia.
Kazusa DNA Research Institute, 2-6-7 Kazusa-Kamatari, Kisarazu, Chiba 292-0818, Japan and Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture Flagship, Waite Campus, Hartley Grove, Urrbrae, South Australia 5064, Australia
Ann Bot. 2015 Mar;115(4):567-80. doi: 10.1093/aob/mcu249. Epub 2014 Dec 22.
Apomixis in plants generates clonal progeny with a maternal genotype through asexual seed formation. Hieracium subgenus Pilosella (Asteraceae) contains polyploid, highly heterozygous apomictic and sexual species. Within apomictic Hieracium, dominant genetic loci independently regulate the qualitative developmental components of apomixis. In H. praealtum, LOSS OF APOMEIOSIS (LOA) enables formation of embryo sacs without meiosis and LOSS OF PARTHENOGENESIS (LOP) enables fertilization-independent seed formation. A locus required for fertilization-independent endosperm formation (AutE) has been identified in H. piloselloides. Additional quantitative loci appear to influence the penetrance of the qualitative loci, although the controlling genes remain unknown. This study aimed to develop the first genetic linkage maps for sexual and apomictic Hieracium species using simple sequence repeat (SSR) markers derived from expressed transcripts within the developing ovaries.
RNA from microdissected Hieracium ovule cell types and ovaries was sequenced and SSRs were identified. Two different F1 mapping populations were created to overcome difficulties associated with genome complexity and asexual reproduction. SSR markers were analysed within each mapping population to generate draft linkage maps for apomictic and sexual Hieracium species.
A collection of 14 684 Hieracium expressed SSR markers were developed and linkage maps were constructed for Hieracium species using a subset of the SSR markers. Both the LOA and LOP loci were successfully assigned to linkage groups; however, AutE could not be mapped using the current populations. Comparisons with lettuce (Lactuca sativa) revealed partial macrosynteny between the two Asteraceae species.
A collection of SSR markers and draft linkage maps were developed for two apomictic and one sexual Hieracium species. These maps will support cloning of controlling genes at LOA and LOP loci in Hieracium and should also assist with identification of quantitative loci that affect the expressivity of apomixis. Future work will focus on mapping AutE using alternative populations.
植物无融合生殖通过无性种子形成产生具有母本基因型的克隆后代。粉苞苣属（菊科）包含多倍体、高度杂合的无融合生殖和有性生殖物种。在无融合生殖的山柳菊属植物中，显性遗传位点独立调控无融合生殖的定性发育成分。在高茎山柳菊中，无减数分裂（LOA）使胚囊在不进行减数分裂的情况下形成，孤雌生殖缺失（LOP）使种子在不依赖受精的情况下形成。在毛叶山柳菊中已鉴定出不依赖受精的胚乳形成所需的位点（AutE）。尽管控制基因尚不清楚，但其他数量性状位点似乎会影响定性位点的外显率。本研究旨在利用从发育中的子房内表达转录本衍生的简单序列重复（SSR）标记，为有性和无融合生殖的山柳菊属物种构建首张遗传连锁图谱。
对显微切割的山柳菊胚珠细胞类型和子房的RNA进行测序，并鉴定SSR。创建了两个不同的F1作图群体，以克服与基因组复杂性和无性繁殖相关的困难。在每个作图群体中分析SSR标记，以生成无融合生殖和有性山柳菊属物种的初步连锁图谱。
开发了一组14684个山柳菊属表达SSR标记，并使用SSR标记的一个子集为山柳菊属物种构建了连锁图谱。LOA和LOP位点均成功定位到连锁群；然而，使用当前群体无法对AutE进行定位。与生菜（莴苣）的比较揭示了这两个菊科物种之间的部分宏观共线性。
为两个无融合生殖和一个有性山柳菊属物种开发了一组SSR标记和初步连锁图谱。这些图谱将有助于克隆山柳菊属中LOA和LOP位点的控制基因，也应有助于鉴定影响无融合生殖表达的数量性状位点。未来的工作将集中于使用替代群体对AutE进行定位。
