中波紫外光联合盐胁迫调控发芽玉米叶黄素富集机理

Eating plant-based foods with rich lutein can protect human eyes from oxidation and high energy lighting damage. Yellow maize is an excellent source of lutein. The previous studies found that UV-B (280–315 nm）and salinity stress could induce lutein accumulation in maize sprouts. However, its mechanism is still unclear to date. The purpose of the proposed project is to fill this gap. It will deeply and systematically investigate influences of UV-B combined with salinity stress on lutein accumulation in cotyledon, plumule, radicle and plumular axis of maize sprouts; identify impacts of jasmonic acid (JA) synthesis inhibitor, Ca2+ channel inhibitor and zeaxanthin synthesis inhibitors on PSY, β-LCY/ε-LCY and β-OHase/ε-OHase activities, as well as protein-gene expression differences, and lutein enrichment in maize sprouts; analyze the effect relationship between endogenous JA level and PSY, the changes of calcium channel protein after Ca2+ flow blockage, and the dependence of ε-LCY/ε-OHase in the α-branch pathway of lutein biosynthesis; reveal bio-regulatory mechanisms of endogenous JA, Ca2+ signaling pathway and α-branch pathway of lutein biosynthesis for its direct accumulation in maize sprouts under UV-B irradiation combined with salinity stress at bio-molecular level; This study will not only create a novel scientific theory of sprout food, but also provide useful technological information for improving its healthy functions.

摄食富含叶黄素的食品可保护人眼免受氧化及高能光线伤害。黄玉米是叶黄素的良好来源，前期研究发现中波紫外光（UV-B）和盐胁迫可诱导发芽玉米叶黄素的积累，但其调控机理尚不明确。针对这一科学问题，本项目系统研究UV-B联合盐胁迫下发芽玉米子叶、胚芽、胚根和胚轴中叶黄素累积规律；探究茉莉酸(JA)合成抑制剂、Ca2+通道抑制剂与玉米黄质合成抑制剂对发芽玉米中PSY、β-LCY/ε-LCY、β-OHase/ε-OHase活性、基因与蛋白组表达的差异及叶黄素富集的影响；解析内源JA水平与PSY的效应关系、细胞Ca2+流受阻后钙通道蛋白的变化及α-分支途径中ε-LCY/ε-OHase的依赖作用，从分子水平上阐明UV-B联合盐胁迫下发芽玉米定向富集叶黄素JA和Ca2+的信号传导作用途径及α-分支途径对叶黄素合成积累的调控机制。该研究既可为开发谷芽类食品创建新的科学理论，又能为增强其保健功能提供技术支撑。

叶黄素是植物光合功能色素，也是人视网膜黄斑色素的主要成分，能够阻止眼晶状体氧化和预防视网膜黄斑变性、降低白内障风险。然而人体自身无法合成叶黄素，必须从膳食中摄取。玉米是全世界总产量最高的重要粮食作物，在我国各地均有栽培，黄色玉米粉中叶黄素含量占总类胡萝卜素的59%。近年来，发芽技术因其速度快、成本低、营养高、无污染等特点，逐渐成为国内外食品研究领域的新热点。本项目研究了发芽玉米不同部位中叶黄素累积规律；探究了外源CaCl2联合UV-B和NaCl定向富集发芽玉米叶黄素的作用机制；解析外源MeJA及其合成抑制剂对叶黄素富集的影响，通过生理生化、类胡萝卜素含量及合成酶基因表达量多角度阐明UV-B联合盐胁迫下发芽玉米定向富集叶黄素调控机制。研究结果表明，种胚、胚根和胚芽中主要类胡萝卜素物质以叶黄素为主，胚芽的总类胡萝卜素含量明显高于胚根和种胚；UV-B和NaCl处理对发芽玉米的生长存在抑制作用，而添加CaCl2可有效促进芽苗生长，同时发芽玉米中类胡萝卜素含量有进一步提高77%；MeJA处理可提高玉米籽粒芽长和发芽率，而其合成抑制剂SHAM可有效抑制发芽玉米体内MeJA合成，从而降低叶黄素含量；同时，外源物质处理下发芽玉米提取物呈现出较强的SOD和POD活性及DPPH和ABTS自由基清除能力，且有部分类胡萝卜素含量具有相关性；通过RT-qPCR测定发芽玉米中类胡萝卜素合成途径中的关键酶基因的表达水平，外源物质通过上调PSY基因表达量影响下游整个合成代谢通量，通过调控LCYB和LCYE基因调控着番茄红素代谢流向α-或β-胡萝卜素，而CYP97C的基因表达量与叶黄素的合成显著相关。本研究从分子水平上解析了中波紫外光联合盐胁迫发芽玉米叶黄素的作用机制，为发芽玉米富集叶黄素提供科学理论和技术支撑。