转录因子EgWRI1s在油棕脂肪酸组分差异形成中的调控机理研究

The oil content of oil palm fruit and its compositions are important agronomic traits. Mesocarp of oil palm fruit is rich in oleic acid and palmitic acid, but its endosperm contains large amounts of lauric acid. The formation mechanism of this difference is unclear. WRI1 is an AP2 type transcriptional factor and a key regulator for oil biosynthesis. The project uses oil palm mesocarp and endosperm as target for the study, and focuses on scientific question that EgWRI1s may play a role in regulating the differential fatty acid composition formation in oil palm mesocarp and endosperm. By using the yeast one-hybrid technology to screen upstream regulatory factors and the downstream target genes for EgWRI1s and the isolated regulatory factors and the promoter of the target genes will be verified by EMSA experiments. Preliminary analytical the factors that may govern the differential expression of EgWRI1s in mesocarp and endosperm; by functional verification of EgWRI1s and screening of target genes in fatty acid synthesis, and learning how these involve in fatty acids synthetic in mesocarp or endosperm which were under the control of EgWRI1-1 or EgWRI1-2; through the traits and target gene mutation investigation and correlation analysis, to verify the role of regulatory factors and target genes in the regulation of oil palm fatty acid synthesis. The study will establish the regulatory network of fatty acid syntheses for EgWRI1s in oil palm, and explores the effects and control mechanisms to resolve EgWRI1’s role regulating the differential fatty acid composition formation of oil palm mesocarp and endosperm, which will enrich the theory of metabolic adjustment of oil content and oil composition in oil palm.

油棕果的含油量及其组分是重要的农艺性状，其中果皮富含棕榈酸和油酸而果仁含大量月桂酸，但差异形成的机制还不清楚。WRI1是AP2类的转录因子，是油脂合成的重要调控因子。本项目以油棕中果皮和果仁为研究对象，围绕EgWRI1s在中果皮和果仁脂肪酸组分差异形成中的调控作用这一科学问题开展研究。通过酵母单杂交技术筛选EgWRI1s的上游调控因子和鉴定下游的靶基因，通过EMSA技术对调控因子和靶基因的启动子进行验证，初步解析EgWRI1s在中果皮和果仁差异表达的调控机制；了解靶基因如何在EgWRI1-1或EgWRI1-2的调控下参与了中果皮和果仁脂肪酸的合成；通过性状与目标基因变异的调查及关联分析，验证调控因子及靶基因在油棕脂肪酸合成调控中的作用。初步建立EgWRI1s的调控网格，解析EgWRI1s在油棕脂肪酸组分差异形成中的调控机理，丰富油棕含油量和油脂组分代谢调节及其性状形成和演变的理论。

油棕具“世界油王”美称，油棕果的含油量及其组分是其重要的农艺性状，其中果皮富含棕榈酸和油酸而果仁含大量月桂酸，但差异形成的机制还不清楚。针对以上问题，本项目开展了油棕AP2类转录因子 EgWRI1s 的上游调控因子的筛选及相关基因家族的全基因组方向，油棕 EgWRI1s 油脂合成相关靶基因的鉴定及其表达特征分析，开展了油棕含油量及组分差异与相关基因变异的相关性分析。相关研究表明EgWRI1-1和EgWRI1-2在时空表达上存在显著的差异,WRI1-1主要在油棕果授粉后81、95和111天的中果皮中的表达量最高，在果仁组织的所有发育阶段及125、142和152天的中果皮的表达极低；WRI1-2的情况正好相反，在在油棕果授粉后81、95和111天的果仁中的表达量最高，在中果皮的所有发育阶段基本不表达。初步筛选到EgWRI1s上游调控因子EgLEC1、EgLEC2、EgABI3、EgFUS3，下游靶基因EgEAR-1、EgEAR-2、EgFATB3、EgFabD等脂肪酸合成相关酶基因与WRI1-2呈现基因共表达，而EgFatB2、EgFatB1、EgHAD-2、EgACC/BCCP-1与WRI1-1呈现基因共表达。通过随机文库分别筛选EgWRI1-1、EgWRI1-2基因的潜在靶基因结合的元件14个和48个，鉴定了其对应的相关联的下游基因；通过64份资源的基因组重测序数据和脂肪酸含量的关联分析，在油棕染色体1（NC_025993.1）上获得4个SNP关联位点，在关联区域附近发现两个醛酮还原酶基因（AKR1）,开发了与脂肪酸合成相关基因的内含子多态性标记13个，其中包括一个WRI1-1-2的等位基因标记。本研究的结果将成为油料作物(特别是非种子器官)脂肪酸合成调控机理的重要补充，同时也将丰富油棕等木本油料作物含油量和油脂组分的代谢调节及性状形成与演变的理论，为油棕油脂组分的品质改良，油棕分子辅助育种的开展提供科学依据。