Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, National Center for Tea Improvement, Tea Research Institute, Chinese Academy of Agricultural Sciences (TRICAAS), Hangzhou, China.
School of Natural and Environmental Sciences, Newcastle University, Newcastle, NE1 7RU, UK.
Plant J. 2019 Mar;97(5):825-840. doi: 10.1111/tpj.14161. Epub 2018 Dec 18.
Cultivars of purple tea (Camellia sinensis) that accumulate anthocyanins in place of catechins are currently attracting global interest in their use as functional health beverages. RNA-seq of normal (LJ43) and purple Zijuan (ZJ) cultivars identified the transcription factor CsMYB75 and phi (F) class glutathione transferase CsGSTF1 as being associated with anthocyanin hyperaccumulation. Both genes mapped as a quantitative trait locus (QTL) to the purple bud leaf color (BLC) trait in F populations, with CsMYB75 promoting the expression of CsGSTF1 in transgenic tobacco (Nicotiana tabacum). Although CsMYB75 elevates the biosynthesis of both catechins and anthocyanins, only anthocyanins accumulate in purple tea, indicating selective downstream regulation. As glutathione transferases in other plants are known to act as transporters (ligandins) of flavonoids, directing them for vacuolar deposition, the role of CsGSTF1 in selective anthocyanin accumulation was investigated. In tea, anthocyanins accumulate in multiple vesicles, with the expression of CsGSTF1 correlated with BLC, but not with catechin content, in diverse germplasm. Complementation of the Arabidopsis tt19-8 mutant, which is unable to express the orthologous ligandin AtGSTF12, restored anthocyanin accumulation, but did not rescue the transparent testa phenotype, confirming that CsGSTF1 did not function in catechin accumulation. Consistent with a ligandin function, transient expression of CsGSTF1 in Nicotiana occurred in the nucleus, cytoplasm and membrane. Furthermore, RNA-Seq of the complemented mutants exposed to 2% sucrose as a stress treatment showed unexpected roles for anthocyanin accumulation in affecting the expression of genes involved in redox responses, phosphate homeostasis and the biogenesis of photosynthetic components, as compared with non-complemented plants.
目前，在将富含花青素的紫茶（Camellia sinensis）品种用作功能性健康饮料方面，全球都对其产生了浓厚的兴趣。对正常（LJ43）和紫娟（ZJ）品种进行的 RNA-seq 研究鉴定出转录因子 CsMYB75 和 phi（F）类谷胱甘肽转移酶 CsGSTF1 与花青素的过度积累有关。这两个基因都作为数量性状位点（QTL）映射到 F 群体中的紫芽叶色（BLC）性状上，CsMYB75 促进了转烟草（Nicotiana tabacum）中 CsGSTF1 的表达。尽管 CsMYB75 提高了儿茶素和花青素的生物合成，但只有花青素在紫茶中积累，表明有选择性的下游调控。由于其他植物中的谷胱甘肽转移酶被认为是类黄酮的转运体（配体），将它们导向液泡沉积，因此研究了 CsGSTF1 在选择性花青素积累中的作用。在茶中，花青素积累在多个小泡中，CsGSTF1 的表达与 BLC 相关，但与儿茶素含量无关，在不同的种质中均如此。拟南芥 tt19-8 突变体（不能表达同源配体 AtGSTF12）的互补恢复了花青素的积累，但未能挽救透明种皮表型，证实 CsGSTF1 不参与儿茶素的积累。与配体功能一致，CsGSTF1 在烟草中的瞬时表达发生在核、细胞质和膜中。此外，用 2%蔗糖作为胁迫处理对互补突变体进行的 RNA-Seq 显示，与未互补的植物相比，花青素积累对涉及氧化还原反应、磷酸盐稳态和光合成分生物发生的基因表达的影响出乎意料。
