【目的】探究不同浓度脱落酸(ABA)对银杏(Ginkgo biloba)叶黄酮类化合物合成的影响,为揭示银杏叶黄酮积累内在机理和叶用林栽培提供理论依据。【方法】以1年生银杏实生苗为试材,在人工气候培养室采用叶面喷施的方法进行外源ABA处理,设置CK(0 μmol/L)、A1(50 μmol/L)、A2(100 μmol/L)、A3(150 μmol/L)和A4(200 μmol/L)5个浓度梯度,测定各处理银杏叶总黄酮及其组分含量和黄酮合成途径关键酶活性,并通过实时荧光定量PCR分析银杏黄酮合成关键酶基因的表达量变化。【结果】ABA处理对银杏叶总黄酮及其组分槲皮素、山柰酚和异鼠李素等的含量产生了显著影响,随着ABA浓度增加,银杏叶总黄酮及其组分含量均呈现先上升后下降的单峰趋势,A3处理总黄酮、槲皮素和异鼠李素含量最高,而A2处理山柰酚含量最高;ABA处理对银杏叶黄酮合成关键酶活性产生了显著影响,但不同酶的变化趋势存在一定差异,苯丙氨酸解氨酶(PAL)活性随ABA浓度增大而逐渐提高,肉桂酸4-羟化酶(C4H)活性与总黄酮含量同步升高和下降,A2、A3处理4-香豆酸CoA连接酶(4CL)活性显著高于对照,而A1、A4处理4CL活性则低于对照;实时荧光定量PCR结果表明,ABA处理可显著提升银杏黄酮合成途径GbPAL、GbC4H、Gb4CL、GbCHS和GbCHI等多个基因的表达水平。总体上,外源ABA能够提高银杏叶黄酮类化合物的合成,其中A3处理效果相对较好。【结论】适宜浓度ABA处理可以通过正向调控多个黄酮合成关键酶基因的表达,提高黄酮合成关键酶的活性,进而促进银杏叶黄酮类化合物的合成和积累。

【Objective】The effects of different concentrations of abscisic acid (ABA) on the synthesis of flavonoids in Ginkgo biloba leaves were examined to provide a theoretical basis upon which the internal mechanisms of flavonoid accumulation in G. biloba leaves and leaf forest cultivation could be revealed.【Method】Annual ginkgo seedlings were placed in an artificial climate culture room and treated with exogenous ABA via foliar spraying at five concentration gradients; 0 μmol/L (CK), 50 μmol/L(A1), 100 μmol/L(A2), 150 μmol/L(A3) and 200 μmol/L(A4). The total flavonoid contents, components of G. biloba leaves, and the activities of key enzymes in the flavonoid synthesis pathway were measured, and the expression changes of key enzyme genes involved in G. biloba flavonoid biosynthesis were analyzed using real-time fluorescence quantitative PCR. 【Result】 ABA treatment had a significant effect on both total flavonoid content and components such as quercetin, kaempferol and isorhamnetin. Increasing the ABA concentration led to an initial increase in the total flavonoid and component content, which was followed by a decrease. The highest total flavonoids, quercetin and isorhamnetin were observed under treatment A3, while the highest kaempferol was associated with A2. ABA treatment had a significant effect on the activities of key enzymes that are involved in flavonoid synthesis in G. biloba leaves (PAL, C4H and 4CL); however, differences were observed in the change trends of the different enzymes. PAL enzyme activity increased gradually as ABA concentrations increased; C4H activity increased and decreased alongside the total flavonoid content; 4CL activity was significantly higher under treatments A2 and A3 than the control; however, 4CL activity was lower under A1 and A4 than the control. The results of real-time fluorescence quantitative PCR showed that ABA treatment significantly improves the expression levels of GbPAL,GbC4H,Gb4CL,GbCHS and GbCHI. In general, exogenous ABA improves the flavonoid synthesis in G. biloba leaves, with the best effects observed under treatment A3.【Conclusion】The use of appropriate ABA concentrations can positively regulate the expression of multiple key enzyme genes that code for flavonoid synthesis, improve the activity of key enzymes involved in flavonoid synthesis, and thus promoting the synthesis and accumulation of flavonoids in G. biloba leaves.