ABA和NO信号对UV-B胁迫下大豆芽菜中异黄酮合成的作用机制

Medium wave of ultraviolet (UV-B) radiation could induce isoflavone accumulation in soybean sprouts. Abscisic acid (ABA) and nitric oxide (NO) were involved in isoflavone accumulation. However, the mechanism is still not clear. The proposed study will systematically investigate ABA and NO signals as well as their interactions on isoflavone biosynthesis and accumulation in soybean sprouts under UV-B stress. Simultaneously, the downstream biomessengers such as cGMP, cADPR and IP3, induced by ABA and NO, and their roles in isoflavone accumulation will also be explored for better understanding the existence of PKG, a target molecule of cGMP, and its role in further induction of cADPR and IP3. Finally, the induction of Ca2+ by UV-B radiation and its involvement in isoflavone accumulation will scientifically reveal functions of the second biomessengers of cGMP, cADPR and IP3. The objectives of this study are to comprehensively investigate the role of network in interactive signaling pathways consisting of ABA and NO and their possible downstream messengers of cGMP, cADPR, IP3 and Ca2+ as well for UV-B-induced isoflavone biosnthesis and accumulation in soybean sprouts at a deep level of enzymatic and molecular mechanisms.

中波紫外光（Medium wave of ultraviolet, UV-B）胁迫可诱导大豆芽菜异黄酮的累积，脱落酸（Abscisic acid, ABA）和一氧化氮（Nitric oxide, NO）信号参与其合成，但其作用机制尚不明确。针对这一科学问题，本项目研究UV-B胁迫下ABA和NO促进大豆芽菜生物合成和累积异黄酮的介导与交互作用、及其对次级信号分子cGMP、cADPR和IP3的诱导作用和机理，探索cGMP作用的受体PKG对cADPR和IP3、以及UV-B对Ca2+的诱导作用和作为cGMP、cADPR及IP3的次级信号转导ABA和NO生物信号在异黄酮合成中的作用，揭示ABA、NO、cGMP、cADPR、IP3、PKG及Ca2+对异黄酮合成关键酶基因的调控效应及组成的网络交互信号通路，从分子水平上揭示UV-B对异黄酮富集的调控的生物信号转导机制。

研究了UV-B胁迫下脱落酸（Abscisic acid, ABA）和NO与其下游信号分子对大豆异黄酮积累的调节作用。UV-B胁迫激活9-顺环氧类胡萝卜素双加氧酶和一氧化氮合酶，促进了ABA和NO的合成。同时，UV-B胁迫下ABA和NO处理显著增加了异黄酮含量，分别为对照的1.4和5.8倍。NO淬灭剂—羧基-2-苯-4,4,5,5-四甲基咪唑-1-氧-3-氧化物（cPTIO）抑制了UV-B胁迫下大豆芽菜中NO的合成，且使异黄酮含量降低32%。可见，ABA和NO是UV-B胁迫下大豆芽菜中异黄酮积累的必要信号分子。同时二者存在互作关系。.研究了环鸟苷酸/蛋白激酶G途径（GC/cGMP）作为ABA和NO的下游信号介导UV-B胁迫诱导大豆异黄酮合成的作用。UV-B胁迫显著促进了大豆芽菜cGMP含量及其合成酶活性。UV-B胁迫下GC抑制剂6-苯胺-5,8-喹啉苯醌（LY83583）使cGMP含量和GC活性及其蛋白表达量下降，ABA、SNP和8-Br-cGMP可逆转此作用。LY83583使异黄酮合成量降低37%。ABA、SNP和8-Br-cGMP可逆转此作用。表明GC/cGMP通过依赖PKG的途径作为ABA和NO的第二信使调控异黄酮的积累。.研究了环腺苷二磷酸核糖（cADPR）作为cGMP/PKG的次级信号进一步传递ABA和NO信号来诱导UV-B胁迫下异黄酮合成的作用。UV-B胁迫显著诱导了大豆芽菜中cADPR和异黄酮的合成，而ABA、SNP和8-Br-cGMP可逆转此效果。cADPR抑制剂烟酰胺使UV-B胁迫下异黄酮含量降低41%，其合成酶活性及其表达量显著降低，ABA、SNP和8-Br-cGMP可逆转此作用。因此，cADPR作为cGMP/PKG的下游信号介导了异黄酮的形成。肌醇三磷酸（IP3）和Ca2+作为cGMP/PKG的次级信号进一步传递ABA和NO信号来诱导UV-B胁迫下大豆异黄酮合成。.综上，本项目揭示了UV-B胁迫下ABA/NO-cGMP/PKG- cADPR/ IP3/Ca2+作为胁迫信号通路促进大豆异黄酮累积的传递途径，为富含异黄酮的大豆芽菜生产及其产业化奠定了理论基础。