Department of Biochemistry, University of Otago, 710 Cumberland St, Dunedin, 9016, New Zealand.
Department of Botany, University of Otago, 464 Great King St, Dunedin, 9016, New Zealand.
BMC Plant Biol. 2018 Sep 24;18(1):206. doi: 10.1186/s12870-018-1423-1.
Asexual seed formation (apomixis) has been observed in diverse plant families but is rare in crop plants. The generation of apomictic crops would revolutionize agriculture, as clonal seed production provides a low cost and efficient way to produce hybrid seed. Hieracium (Asteraceae) is a model system for studying the molecular components of gametophytic apomixis (asexual seed reproduction).
In this study, a reference transcriptome was produced from apomictic Hieracium undergoing the key apomictic events of apomeiosis, parthenogenesis and autonomous endosperm development. In addition, transcriptome sequences from pre-pollination and post-pollination stages were generated from a loss of parthenogenesis (lop) mutant accession that exhibits loss of parthenogenesis and autonomous endosperm development. The transcriptome is composed of 147,632 contigs, 50% of which were annotated with orthologous genes and their probable function. The transcriptome was used to identify transcripts differentially expressed during apomictic and pollination dependent (lop) seed development. Gene Ontology enrichment analysis of differentially expressed transcripts showed that an important difference between apomictic and pollination dependent seed development was the expression of genes relating to epigenetic gene regulation. Genes that mark key developmental stages, i.e. aposporous embryo sac development and seed development, were also identified through their enhanced expression at those stages.
The production of a comprehensive floral reference transcriptome for Hieracium provides a valuable resource for research into the molecular basis of apomixis and the identification of the genes underlying the LOP locus.
有性种子形成（无融合生殖）在不同的植物科中都有观察到，但在作物中很少见。无融合生殖作物的产生将彻底改变农业，因为克隆种子生产提供了一种低成本、高效的方式来生产杂交种子。菊（菊科）是研究配子体无融合生殖（无性种子繁殖）分子组成的模式系统。
在这项研究中，从经历无融合生殖关键事件的无融合生殖杂种菊中产生了一个参考转录组，这些事件包括无减数分裂、孤雌生殖和自主胚乳发育。此外，还从表现出无融合生殖和自主胚乳发育丧失的部分无融合生殖（lop）突变体中产生了授粉前和授粉后阶段的转录组序列。转录组由 147632 个连续序列组成，其中 50%被注释为同源基因及其可能的功能。该转录组用于鉴定无融合生殖和授粉依赖（lop）种子发育过程中差异表达的转录本。差异表达转录本的基因本体论富集分析表明，无融合生殖和授粉依赖种子发育之间的一个重要区别是与表观遗传基因调控相关的基因表达。通过在这些阶段增强表达，还鉴定了标记关键发育阶段的基因，即无孢子胚囊发育和种子发育。
为菊属植物生成全面的花部参考转录组为研究无融合生殖的分子基础和鉴定 lop 基因座的基因提供了有价值的资源。
