The biosynthesis of EGCG, theanine and caffeine in response to temperature is mediated by hormone signal transduction factors in tea plant (Camellia sinensis L.)

Abstract

As the main flavor components of tea, the contents of epigallocatechin-3-gallate (EGCG), theanine and caffeine are regulated by ambient temperature. However, whether the biosynthesis of EGCG, theanine and caffeine in response to temperature is regulated by endogenous hormones and its mechanism is still unclear. In this study, tea cuttings cultivated in the phytotron which treated at different temperatures 15℃, 20℃, 25℃ and 30℃, respectively. The UPLC and ESI-HPLC-MS/MS were used to determine the contents of EGCG, theanine, caffeine and the contents of phytohormones in one leaf and a bud. The results showed that indoleacetic acid (IAA), gibberellin 1(GA1) and gibberellin 3 (GA3) were significantly correlated with the content of EGCG; Jasmonic acid (JA), jasmonate-isoleucine (JA-Ile) and methyl jasmonate (MeJA) were strongly correlated with theanine content; IAA, GA1 and gibberellin 4 (GA4) were significantly correlated with caffeine content at different temperatures. In order to explore the internal intricate relationships between the biosynthesis of these three main taste components, endogenous hormones, and structural genes in tea plants, we used multi-omics and multidimensional correlation analysis to speculate the regulatory mechanisms: IAA, GA1 and GA3 up-regulated the expressions of chalcone synthase (CsCHS) and trans-cinnamate 4-monooxygenase (CsC4H) mediated by the signal transduction factors auxin-responsive protein IAA (CsIAA) and DELLA protein (CsDELLA), respectively, which promoted the biosynthesis of EGCG; IAA, GA3 and GA1 up-regulated the expression of CsCHS and anthocyanidin synthase (CsANS) mediated by CsIAA and CsDELLA, respectively, via the transcription factor WRKY DNA-binding protein (CsWRKY), and promoted the biosynthesis of EGCG; JA, JA-Ile and MeJA jointly up-regulated the expression of carbonic anhydrase (CsCA) and down-regulated the expression of glutamate decarboxylase (CsgadB) mediated by the signal transduction factors jasmonate ZIM domain-containing protein (CsJAZ), and promoted the biosynthesis of theanine; JA, JA-Ile and MeJA also jointly inhibited the expression of CsgadB mediated by CsJAZ via the transcription factor CsWRKY and AP2 family protein (CsAP2), which promoted the biosynthesis of theanine; IAA inhibited the expression of adenylosuccinate synthase (CspurA) mediated by CsIAA via the transcription factor CsWRKY; GA1 and gibberellin 4 (GA4) inhibited the expression of CspurA mediated by CsDELLA through the transcription factor CsWRKY, which promoted the biosynthesis of caffeine. In conclusion, we revealed the underlying mechanism of the biosynthesis of the main taste components in tea plant in response to temperature was mediated by hormone signal transduction factors, which provided novel insights into improving the quality of tea.

Selenium-Mediated (−)-Epigallocatechin-3-Gallate Dynamics via Flavanone-3-Hydroxylase Regulation of Flavonoid Biosynthesis in Fu Tea (Camellia sinensis (L.) O. Kuntze)

“…Ethylamine and glutamate are used as substrates in the theanine biosynthesis catalyzed by theanine synthase . Theanine biosynthesis was positively regulated by citrate synthase and theanine synthetase and negatively regulated by glutamine synthetase . Selenium may decrease the conversion of glutamate to theanine by downregulating the expression of theanine synthetase or increasing the expression of glutamine synthetase, thus affecting the biosynthesis of theanine and decreasing the amino acid content, as compared to ordinary Fu tea (Figure ).…”

Recent Advances in the Specialized Metabolites Mediating Resistance to Insect Pests and Pathogens in Tea Plants (Camellia sinensis)

“…As the most well-known purine alkaloid, caffeine (1,3,7-trimethylxathine) accumulates at higher levels in the tea bud and young leaves, and its biosynthesis involves several critical methylation reactions catalyzed by N-methyl transferases and a 7-methylxanthine nucleosidase [ 83 ]. Caffeine is not only closely related to nitrogen metabolism, but it also plays an important role in the direct defense against insect herbivores and pathogens [ 84 , 85 , 86 , 87 ]. An E. obliqua attack activated the caffeine biosynthesis and increased its accumulation, while an E. onukii infestation did not change the levels of caffeine.…”

“…Theanine is mainly distributed in roots, followed by young leaves, stems, flowers, and old leaves, and it is synthesized from L-glutamic acid and ethylamine by the catalytic action of theanine synthase [ 17 ]. Theanine is closely related to nitrogen assimilation and metabolism [ 86 , 88 ]. In light of the important association between basic amino acids and theanine and nitrogen metabolism, the levels of theanine and eight basic amino acids (glutamate, serine, cysteine, tyrosine, methionine, phenylalanine, glycine, and lysine) were variably induced upon the attack of E. obliqua .…”

Application of Multi-Perspectives in Tea Breeding and the Main Directions

“…The interaction between hormones and metabolites within the tea plants also influenced quality, as the expression of CsJAZ6 in tea plants inhibited the JA pathway, which regulated most secondary metabolites, notably catechins, and the interaction between CsJAZ6 and catechin biosynthesis regulators negatively regulated catechin accumulation [ 178 ]. Apart from endogenous hormones, endogenous hormone signaling factors could also mediate the synthetic pathways of caffeine, EGCG and theanine to respond to temperature and improve the quality of tea leaves [ 179 ]. The diurnal temperature difference at 10 °C clearly affected primary and secondary metabolites, with the lowest levels of polyphenols and catechins and higher levels of amino acid and theanine synthase expression, but the actual application on a certain scale was still constrained by the environment and climate [ 180 ].…”

“…ECGT UGGT Shikimate pathway [204,205] tea leaves [179]. The diurnal temperature difference at 10 • C clearly affected primary and secondary metabolites, with the lowest levels of polyphenols and catechins and higher levels of amino acid and theanine synthase expression, but the actual application on a certain scale was still constrained by the environment and climate [180].…”