芒果蔗糖代谢酶及关键基因协同表达模式分析

Many stress-resistance mango germplasms could not be accepted as commercial cultivars, due to the low level content of soluble sugars that result in tasteless fruits. Sucrose, the main component of soluble sugar, determines the quality of flavor. However, the metabolic regulation mechanism in mango is not clear. Previously, mango cultivar with high sugar content was hybridized with low sugar genotype, and their F1 progenies were obtained in our team. In the present project, the contents of soluble sugars, the activities of sucrose metabolism enzymes, and the expression level of genes related to sucrose metabolism enzymes will be detected continuously during fruit developing period for the male parent, the female parent and strains of F1 population. The values of soluble sugar contents will be transferred as sweetness values, which in turn will be compared between progenies and parents for accessing the sweetness heritance as a mid-parent, near female parent, near male parent or super-parents value trait. With the sweetness value as dependent variable, while the activity value of each enzyme and the expression level of each gene as independent variables, the Principal Component Analysis, the Correlation Analysis, and the Redundancy Analysis combined with Screen Stepwise Regression Analysis (RDA-SSRA) will be performed. The key enzymes and the key genes will be screened out via those analyses; meanwhile, the functional models will be generated for illustrating the relationships of independent variables and dependent variables. The above results will reveal the hereditary feature of mango sweetness trait; screen out the key enzymes and the key genes related to sugar metabolism, as well as their influence on sweetness. Therefore, to conduct this project could increase the knowledge of physiology and heredity on the regulation of sugar metabolism, which will benefit for genetic improvement of mango.

低糖味淡导致许多抗性优良的芒果品种失去商品价值。可溶性糖的主要成分蔗糖决定着芒果风味品质，但其代谢调控机制尚不清楚。本项目依托单位将高蔗糖型与自主选育的低蔗糖型芒果品种杂交获得了F1代群体。本项目拟对果实发育过程中父本、母本和F1代多个株系的果实可溶性糖组分含量、蔗糖代谢酶活性及其相关基因表达量进行跟踪测定。根据糖组分含量计算甜度值，并绘制亲代、子代甜度值分布图，判断该性状属于偏亲(父/母)、超亲还是中亲值遗传。以甜度值为因变量，各个酶活性和各个基因表达量均为自变量，进行主成分分析、相关性分析、冗余串联逐步回归分析，得到影响甜度值的蔗糖代谢关键酶和关键基因，并建立反映自变量对因变量作用方式的函数模型。研究结果将揭示芒果果实甜度性状遗传特征，锚定蔗糖积累关键酶、关键基因以及它们对甜度的作用方式，以丰富芒果蔗糖代谢调控的生理和遗传基础，为芒果高抗种质遗传改良提供依据，具有理论与实践双重意义。

低糖味淡导致许多抗性优良的芒果品种失去商品价值。可溶性糖决定着芒果风味品质，但其代谢调控机制尚不清楚。本研究以高甜度的台农1号和低甜度的热农1号为试材，探讨芒果糖积累的生理和分子机理。主要结论有：①对芒果果实发育阶段可溶性糖及其相关指标含量变化规律进行了分析，发现‘热农1号’的果糖和葡萄糖含量从花后50d开始缓慢上升并最终于花后130 d达到最大值；蔗糖含量在花后110-130d时蔗明显增加；淀粉含量在果实膨大期（花后65-80d）快速大量积累，显著提升至最大值。‘台农1号’果糖和总糖幼果到膨大期呈W形上升，随后小幅上升至采摘成熟；蔗糖在花后112天之后显著上升；葡萄糖在幼果期明显积累；淀粉含量随着果实的发育至采摘成熟先增加后降低。这些变化与两者的甜度差异相对应。②通过对芒果果实发育阶段糖代谢相关酶活性变化规律分析发现，‘热农1号’果实发育过程中，β-淀粉酶的活性始终远远高于α-淀粉酶活性；磷酸葡萄糖变位酶（PGM）在所测的众多酶中的活性水平最高，并在果实膨大期达到峰值；‘台农1号’果实发育过程异淀粉酶（Isoamylase）活性在果实采摘成熟期显著高于幼果期。③通过利用R语言进行数模构建，分别得到了热农1号和台农1号，以及二者综合数据的甜度值、果糖、葡萄糖、蔗糖对应的数学模型回归方程，实现了用数学语言表达各因素对芒果甜度及主要糖成分的影响程度。同时通过关系网络图的构建，实现了各因素对芒果甜度及主要糖成分影响程度的可视化。进一步阐明了芒果果实可溶性糖积累和转化的生理及分子基础，④通过代谢组和转录组联合分析探明了芒果糖代谢的六大通路，并筛选了一批候选关键基因。⑤对果糖激酶关键基因进行了全长克隆和基因结构、编码氨基酸序列的差异分析。以上研究结果探讨了高、低糖芒果甜度差异的生理和分子机理，为芒果优质栽培措施的改进或利用分子手段调节和改造芒果果实糖积累和转化提供理论和技术参考。