白茶萎凋过程中儿茶素合成关键酶基因表达分析

Expression of genes encoding key enzymes in biosynthesis pathways of catechins in the withering process of white tea

【目的】研究白茶萎凋过程中茶多酚、儿茶素组分含量变化与其合成途径中关键酶基因的动态表达,为优化白茶的萎凋工艺提供参考依据。【方法】以不同萎凋阶段的白茶为原料,分别采用福林酚(Folin-Ciocalten)比色法和高效液相色谱法(HPLC)测定茶多酚、儿茶素组分含量的变化,并以实时荧光定量PCR检测白茶萎凋过程中与儿茶素物质代谢合成相关基因(PAL、C4H、CHS、CHI、F3'5'H、F3'H、F3H、DFR、LAR、ANS、ANR和UGGT)的相对表达量。【结果】白茶萎凋过程中茶多酚含量呈逐渐降低趋势,儿茶素组分中表儿茶素(EC)、没食子儿茶素(GC)、表没食子儿茶素(EGC)、表儿茶素没食子酸酯(ECG)含量整体上呈先上升后下降的变化趋势,且均在萎凋历时32 h出现最大值。实时荧光定量PCR检测结果表明,儿茶素生物合成途径关键酶基因PAL、C4H、CHI、F3H、F3'H、F3'5'H、DFR、LAR、ANR和UGGT均在萎凋历时32 h呈上调表达,CHS基因则随萎凋历时的增加呈下调表达趋势,ANS基因表达在整个萎凋过程中呈先上升后下降的变化趋势,在萎凋历时16 h达最大值。白茶萎凋过程中儿茶素合成途径关键基因表达水平具有调控儿茶素生物合成的作用。【结论】在白茶萎凋过程中,儿茶素生物合成途径关键酶基因PAL、C4H、F3H、F3'H、DFR、LAR、ANR的表达与儿茶素组分单体EC、GC、EGC的积累规律基本一致,其最大值均出现在萎凋历时32 h,因此在制茶时可适当缩短萎凋时长,以提高白茶品质。

[Objective]The present experiment was conducted to investigate change of contents of tea polyphel and catechins components in withering process of white tea as well as dynamic expression of genes encoding key enzymes in their biosynthesis pathways, in order to provide theoretical basis for optimizing withering craft of white tea. [Method]Using white tea at different stages of withering as materials, the contents of tea polyphel and cateehins components in biosynthe- sis pathways of catechins were determined in leaves by Folin-phenol（Folin-Ciocalten） colorimetric method and HPLC. The expression quantities of key enzymes genes（PAL, CdH, CHS, CHI, FY5＇H, FYH, F3H, DFR,LAR,ANS,ANR and UGOT） in biosynthesis pathways of eateehins was determined by real-time quantitative ECR. [Result]The results showed that, tea polyphel content was decreased gradually. The contents of eateehins components including epieatechin （EC）, gallocat- eehin（GC）, epigalloeateehin（EGC） and epigalloeatechin gallate（ECG） first decreased and then increased, reaching max- imum at 32 h after withering. The results of real-time PCR showed that, the expression quantity of key genes AL, C4H, CHI, F3H, FYH,F3＇5＇H, DFR, LAR,ANR, UGGT in biosynthesis pathways of eateehins increased at 32 h after withering, the expression quantity of CHS gene decreased as duration of withering increased. The expression quantity of ANS gene first decreased and then increased, reaching maximum at 16 h after withering. Furthermore, the expression quantities of genes encoding key enzymes played an important role in regulating biosynthesis pathways of cateehins. [Conclusion]In withering process of white tea, the expression of key genes PAL, CdH, F3H, FYH, DFR, LAR, ANR in biosynthesis pathways of cateehins is consistent with the accumulation law of catechins components（EC, GC, EGC）, reaching maxi- mum at 32 h after withering. Therefore, in order to improve quality of white tea, the duration of withering should be short- ened in manufacture of tea.