Comparative Transcriptomic Analysis Reveals Regulatory Mechanisms of Theanine Synthesis in Tea (Camellia sinensis) and Oil Tea (Camellia oleifera) Plants

Abstract

Tea provides a rich taste and has healthy properties due to its variety of bioactive compounds, such as theanine, catechins, and caffeine. Theanine is the most abundant free amino acid (40%−70%) in tea leaves. Key genes related to theanine biosynthesis have been studied, but relatively little is known about the regulatory mechanisms of theanine accumulation in tea leaves. Herein, we analyzed theanine content in tea (Camellia sinensis) and oil tea (Camellia oleifera) and found it to be higher in the roots than in other tissues in both species. The theanine content was significantly higher in tea than oil tea. To explore the regulatory mechanisms of theanine accumulation, we identified genes involved in theanine biosynthesis by RNA-Seq analysis and compared theanine-related modules. Moreover, we cloned theanine synthase (TS) promoters from tea and oil tea plants and found that a difference in TS expression and cis-acting elements may explain the difference in theanine accumulation between the two species. These data provide an important resource for regulatory mechanisms of theanine accumulation in tea plants.

Characterization of l-Theanine Hydrolase in Vitro and Subcellular Distribution of Its Specific Product Ethylamine in Tea (Camellia sinensis)

“…35 Until now, most of the studies on the theme of L-theanine metabolism in tea plants have been focused mainly on the genes involved in L-theanine synthesis and the possible transcription factors governing their transcription. 36,37 Few studies have investigated the role of L-theanine catabolism in Ltheanine accumulation and its regulatory mechanism in the developing tea plant or in response to biotic and abiotic stress.…”

“…In addition to tea varieties, many other factors such as growing conditions, location, and harvest time could affect the l -theanine content accumulation in tea leaves. − Matsuura and Kakuda in 1990 found that illumination and temperature strongly affected l -theanine accumulation in tea callus . Until now, most of the studies on the theme of l -theanine metabolism in tea plants have been focused mainly on the genes involved in l -theanine synthesis and the possible transcription factors governing their transcription. , Few studies have investigated the role of l -theanine catabolism in l -theanine accumulation and its regulatory mechanism in the developing tea plant or in response to biotic and abiotic stress. It has been reported that PDX2 in Arabidopsis could be regulated by high light, chilling, drought, and ozone .…”

Gene Coexpression Network Reveals Insights into the Origin and Evolution of a Theanine-Associated Regulatory Module in Non-Camellia and Camellia Species

“…The first way is based on the motif prediction of 2000 bp promoter sequence upstream of TS1 to find the possible gene families . The second way is to choose TFs with a rational correlation threshold in the gene coexpression network. , The promoter analysis based on known TFs-motif evidence is limited because of the completeness of the TFs–motif relationship collected in the related databases, such as PlantCARE and JASPAR . For example, there is no report on the binding motif of AtLBD38 , although it can inhibit the expression of AtGS1.4 in A.…”

“…61 The second way is to choose TFs with a rational correlation threshold in the gene coexpression network. 41,61 The promoter analysis based on known TFsmotif evidence is limited because of the completeness of the TFs−motif relationship collected in the related databases, such as PlantCARE 62 and JASPAR. 63 For example, there is no report on the binding motif of AtLBD38, although it can inhibit the expression of AtGS1.4 in A. thaliana.…”

Glutamine Synthetases Play a Vital Role in High Accumulation of Theanine in Tender Shoots of Albino Tea Germplasm “Huabai 1”

“…The mechanism of accumulation of theanine in tender shoots of albino tea plants has not been well elucidated. Although theanine is synthesized in most tissues, it is significantly higher in young buds and roots of tea. , Agronomic practices also contribute to the synthesis of theanine. Shading increases theanine contents and decreases epicatechin and epigallocatechin contents, thus producing high-quality green tea …”