Genetics of microspore embryogenesis and doubled haploid development in rapeseed (Brassica napus L.)

目前，利用该方法制备的小孢子胚胎发生和双单倍体系在实际育种中具有重要意义，尤其是在基础研究中。另一方面，对于小孢子在胚胎发生过程中发生的分子过程，以及控制胚胎发生潜力的基因，即小孢子形成胚胎的倾向，目前所知不多。小孢子的胚胎发生潜力是限制小孢子胚胎发生的主要因素，不同基因型的小孢子胚胎发生潜力差异很大。在一个DFG项目中，已经鉴定了许多品种间替代系（isl），它们的胚胎发生潜力比复发亲本高40倍。ISL是通过标记辅助选择在供体和复发亲本的反复回交中产生的，并且在复发亲本的遗传背景中只携带供体基因组的一个或几个片段。因此，isl仅在少数明确的基因组区域与复发亲本存在遗传差异。在建议的项目中，将更详细地分析4个选定的ISLs。这包括使用MACE分析对胚胎发生诱导过程中的转录谱进行比较分析，并鉴定可能负责增强胚胎发生潜力的候选基因。候选基因的转录谱将通过qRT-PCR分析进行验证。此外，从这4条线的进一步回交中，将开发出新的isl，它将只携带原始线供体段的单个（重叠的子）片段。新的ISL将允许对负责在原始系中观察到的增强胚胎发生潜力的遗传因素进行精细绘图。最后，MACE分析的转录本和新ISL的供体片段将被映射到油菜籽A和C基因组的基因组序列上，以便整合遗传和转录研究的结果。

Today microspore embryogenesis and the doubled haploid lines developed by this process are of great importance in practical breeding but especially in basic re-search. On the other hand, not much is currently known about the molecular pro-cesses that occur in microspores during the induction of embryogenesis or about the genes that govern the embryogenic potential, that is the tendency of the microspores to form embryos. The embryogenic potential of the microspores is the main factor limiting microspore embryogenesis and varies widely between genotypes. In a DFG project a number of intervarietal substitution lines (ISLs) have been identified, which show an up to 40x higher embryogenic potential than the recurrent parent. ISL are produced by marker assisted selection in a recurring backcrossing of a donor and recurrent parent and carry only one or a few segments of the donor genome in the genetic background of the recurrent parent. ISLs are, therefore, genetically different from the recurrent parent only in a few well defined genomic regions. In the proposed project 4 selected ISLs shall be analysed in more detail. This includes a comparative analysis of transcriptional profiles during the induction of embryogenesis using MACE analyses and the identification of candidate genes that may be responsible for the enhanced embryogenic potential of the lines. The transcription profiles of the candi-date genes will then be verified by qRT-PCR analysis. In addition, from further back-crosses of the 4 lines, new ISLs shall be developed, which will carry only single (overlapping sub-) segments of the donor segments of the original lines. The new ISL will allow a fine mapping of the genetic factors responsible for the enhanced embryo-genic potential observed in the original lines. Finally, the transcripts from the MACE analyses and the donor segments of the new ISL will be mapped on the genomic sequences of the A and C genomes of rapeseed to allow an integration of the results from the genetic and transcriptional studies.