基于遗传基因组学解析干旱调控小麦茎秆果聚糖代谢转运的分子遗传机制

Fructan, as a major component of water soluble carbohydrates (WSC) transiently reserved in shoots of wheat, plays a critical role in involvement in WSC remobilization regulated by drought for effectively compensating grain-filling. But its genetic mechanism is not still clear. In present research, based on our previous research and using the strategy of genetic genomics, main shoots between two mapping parents will be utilized to transcriptome sequencing, mainly identifying differential genes greatly associated with key enzyme genes of fructan metabolism and high-abundant expression in drought stress. Using an ILs population from two parents backcross and its high-density genetic map, a whole genome scanning will perform to detect eQTLs for relative expression amounts of these differential genes and pQTLs for related traits to fructan metabolism and remobilization in shoots to compensate grain-filling. It will further dissect the characteristics of common and differential expressions and confirm QTLs hot-spot regions with carrying functional genes. The co-expression analysis of cis-eQTLs and trans-eQTLs will be performed to construct the regulation networks of functional gene expressions for shoot fructan metabolism and remobilization in response to drought stress, which will finally unravel the intrinsic relationship from traits to QTLs and genes, further elucidate the molecular genetic mechanism for drought-regulated fructan metabolism and remobilization in shoots. The results would be expected to build up the critical theory and technique basis for the molecular genetic improvement of drought tolerance in wheat.

果聚糖作为小麦茎秆中暂贮性可溶性碳水化合物（WSC）的主要存在形式，在参与干旱调控WSC代谢转运有效补偿籽粒灌浆中起重要作用，但其遗传机制仍不清楚。为此，本研究基于前期研究基础，借助遗传基因组学策略和手段，通过亲本间主茎转录组测序分析，鉴定干旱胁迫条件下高丰度表达且与果聚糖代谢关键酶基因高度关联的差异基因；利用两亲本构建的ILs群体及其高密度遗传图谱，对这些差异基因的表达量和茎秆果聚糖代谢转运相关性状分别进行eQTLs和pQTLs全基因组扫描定位，剖析目标QTLs在不同水分条件下的共性表达和差异表达，确定QTLs热点区域及其承载的功能基因；通过cis-eQTLs和trans-eQTLs共表达分析，构建果聚糖代谢转运功能基因表达调控网络，揭示“性状→QTLs→基因”的内在关系，阐明干旱调控茎秆果聚糖代谢转运的分子遗传机制，以期为小麦抗旱分子遗传改良等奠定理论基础和技术支撑。

本研究借助遗传基因组学策略和手段，通过小麦ILs群体亲本间主茎转录组测序分析，鉴定与果聚糖代谢相关差异基因，并对茎秆果聚糖代谢转运相关性状进行QTLs定位和共表达分析，确定QTLs热点区域，预测候选基因，构建基因表达调控网络，解析了干旱调控茎秆果聚糖代谢转运的分子遗传机制，以期为小麦抗旱分子遗传改良等奠定理论基础和技术支撑。研究结果如下：.（1）通过主茎转录组测序和表达分析发现，在干旱胁迫条件下，晋麦47和西峰20间检测到7417个差异基因，其中上调基因有3181个，下调基因有4236个。在糖代谢和碳代谢中，西峰20的上调基因主要参与了淀粉和蔗糖代谢，而晋麦47中的上调基因则主要参与了碳代谢。.（2）在两种水分条件下，共检测到168个控制小麦茎秆果聚糖代谢转运相关性状的pQTLs和133个控制小麦果聚糖代谢关键酶基因的eQTLs，这些位点主要受晋麦47的等位基因的调控，并且在不同水分环境条件下表达模式不同，但干旱胁迫在一定程度上限制了QTL表达。通过共表达分析，检测到30个cis-QTLs和103个trans-QTLs。.（3）整合目标性状pQTLs和eQTLs，成功构建了QTLs一致性图谱，鉴定到38个QTL热点区域。通过对5个重要热点区域基因鉴定，共得到923个候选基因，其中有28个候选基因参与调控糖代谢途径，这些基因在小麦不同发育阶段茎秆中普遍高表达。.（4）基于eQTL定位和侧翼标记信息，构建小麦茎秆果聚糖代谢转运功能基因表达调控网络。在该调控网络中，SPP基因可能是小麦茎秆果聚糖代谢的主调控因子。该基因有3个同源基因，分别位于5A、5B和5D染色体上。通过TaSPP-5A单倍型分析发现，TaSPP-5Aa表达量显著高于TaSPP-5Ab，且与茎秆蔗糖高含量和高千粒重高度相关，该优异单倍型在育种中被长期正向选择，在改善小麦产量性状方面起到重要作用。