Abstract
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.
Highlights
IntroductionTremendous attention has been focused on tea plant due to its pleasant flavor and bioactive substances
The pronounced changes in the proteomic profile between tender purple leaf (TPL) and mature green leaf (MGL) tissues were included: 1) the lower activity of proteins associated with CO2 assimilation, energy metabolism and photo flux efficiency and higher content of anthocyanins in TPL samples may protect tender leaves against photo-damage; 2) the higher abundance of CHS, CHI and FLS likely contributes to the synthesis of anthocyanins, catechins and flavonols in TPL tissues; 3) higher abundance of stress response proteins, such as GST and PHGPx, could enhance the tolerance of TPL tissues to adverse condition; 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
The results revealed that the higher abundance of two key proteins including CHS and CHI were responsible for the higher content of anthocyanins in TPL tissues compared with MGL ones
Summary
Tremendous attention has been focused on tea plant due to its pleasant flavor and bioactive substances. Tea leaves are a valuable source of secondary metabolic products, including flavonoids, alkaloids, polysaccharides and theanine [2]. Among these secondary metabolites, flavonoids (which comprise polyphenols, flavones, flavanonols and anthocyanins) are considered to contribute numerous pharmacological beneficial effects on human health [3,4]. The health benefits of tea are thought to account for tea’s protective role against cardiovascular disease [3], atherosclerosis [4], oxidant activity [5], and cancer [6]
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