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

目前，小孢子胚胎发生及其获得的加倍单倍体品系在实际育种中具有重要意义，尤其在基础研究中具有重要意义。另一方面，关于小孢子在胚胎发生诱导过程中发生的分子过程或控制胚胎发生潜力的基因，即小孢子形成胚胎的趋势，目前还知之甚少。小孢子的胚胎发生能力是限制小孢子胚胎发生的主要因素，并且在不同的基因型之间差异很大。在DFG项目中，已经确定了许多品种间替代系(ISL)，它们显示出比轮回亲本高40倍的胚胎发生潜力。ISL是在供体和轮回亲本的重复回交中通过标记辅助选择产生的，在轮回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，ISLS与轮回亲本只有在少数几个明确定义的基因组区域上存在遗传差异。在拟议的项目中，应更详细地分析选定的4个国际执行计划。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，以及识别可能导致这些品系胚胎发生潜力增强的候选基因。然后将通过qRT-PCR分析来验证坎迪-Date基因的转录图谱。此外，通过4个品系的进一步回交，应开发新的ISL，它将仅携带原始品系供体片段的单个(重叠的亚)片段。新的ISL将允许对导致在原始品系中观察到的胚胎基因潜力增强的遗传因素进行精细定位。最后，来自MACE分析的转录本和新ISL的供体片段将被映射到油菜A和C基因组的基因组序列上，以便将遗传和转录研究的结果整合在一起。

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.