Zhou Qiongqiong, Chen Zhidan, Lee Jinwook, Li Xinghui, Sun Weijiang
Anxi College of Tea Science, Fujian Agriculture and Forestry University, Fuzhou, China.
College of Horticulture, Henan Agricultural University, Zhengzhou, China.
PLoS One. 2017 May 16;12(5):e0177816. doi: 10.1371/journal.pone.0177816. eCollection 2017.
Tea products made from purple leaves are highly preferred by consumers due to the health benefits. This study developed a proteome reference map related to color changes during leaf growth in tea (Camellia sinensis) plant with purple young shoots using two-dimensional electrophoresis (2-DE). Forty-six differentially expressed proteins were detected in the gel and successfully identified by using MALDI-TOF/TOF-MS. The pronounced changes in the proteomic profile between tender purple leaves (TPL) and mature green leaves (MGL) included: 1) the lower activity of proteins associated with CO2 assimilation, energy metabolism and photo flux efficiency and higher content of anthocyanins in TPL than those in MGL may protect tender leaves against photo-damage; 2) the higher abundance of chalcone synthase (CHS), chalcone isomerase (CHI) and flavonol synthase (FLS) likely contributes to the synthesis of anthocyanins, catechins and flavonols in TPL tissues; 3) higher abundance of stress response proteins, such as glutathione S-transferases (GST) and phospholipid hydroperoxide glutathione peroxidase (PHGPx), could enhance the tolerance of TPL tissues to adverse condition in; and 4) the increased abundance of proteins related to protein synthesis, nucleic acids and cell wall proteins should be beneficial for the proliferation and expansion of leaf cell in TPL tissues. qPCR analysis showed that the expression of differentially abundant proteins was regulated at the transcriptional level. Therefore, the results indicated that higher abundance of CHI and CHS may account for the production of the purple-shoot phenotype in Wuyiqizhong 18 and thereby, enhancing the anthocyanin biosynthesis. The higher abundance of glutamine synthetase (GS) proteins related to the theanine biosynthesis may improve the flavor of tea products from TPL materials. Thus, this work should help to understand the molecular mechanisms underlying the changes in leaf color alteration.
由于对健康有益，由紫色叶片制成的茶产品深受消费者喜爱。本研究利用二维电泳（2-DE）技术，构建了一个与茶树（Camellia sinensis）紫色嫩梢叶片生长过程中颜色变化相关的蛋白质组参考图谱。在凝胶中检测到46种差异表达蛋白，并通过基质辅助激光解吸电离飞行时间串联质谱（MALDI-TOF/TOF-MS）成功鉴定。嫩紫色叶片（TPL）和成熟绿色叶片（MGL）之间蛋白质组图谱的显著变化包括：1）与二氧化碳同化、能量代谢和光通量效率相关的蛋白质活性较低，且TPL中花青素含量高于MGL，这可能保护嫩叶免受光损伤；2）查尔酮合酶（CHS）、查尔酮异构酶（CHI）和黄酮醇合酶（FLS）的丰度较高，可能有助于TPL组织中花青素、儿茶素和黄酮醇的合成；3）应激反应蛋白，如谷胱甘肽S-转移酶（GST）和磷脂氢过氧化物谷胱甘肽过氧化物酶（PHGPx）的丰度较高，可增强TPL组织对逆境的耐受性；4）与蛋白质合成、核酸和细胞壁蛋白相关的蛋白质丰度增加，应有利于TPL组织中叶细胞的增殖和扩展。定量聚合酶链反应（qPCR）分析表明，差异丰富蛋白的表达在转录水平上受到调控。因此，结果表明，CHI和CHS的较高丰度可能是造成武夷奇种18紫色芽梢表型的原因，从而增强了花青素的生物合成。与茶氨酸生物合成相关的谷氨酰胺合成酶（GS）蛋白的较高丰度可能改善TPL材料制成的茶产品的风味。因此，这项工作应有助于理解叶片颜色变化背后的分子机制。
