Tea (Camellia sinensis) is the most widely consumed beverage aside from water. The flavor of tea is conferred by certain metabolites, especially l-theanine, in C. sinensis. To determine why more l-theanine accumulates in C. sinensis than in other plants, we compare l-theanine contents between C. sinensis and other plant species (Camellia nitidissima, Camellia japonica, Zea mays, Arabidopsis thaliana, and Solanum lycopersicum) and use a stable isotope labeling approach to elucidate its biosynthetic route. We quantify relevant intermediates and metabolites by mass spectrometry. l-Glutamic acid, a precursor of l-theanine, is present in most plants, while ethylamine, another precursor of l-theanine, specifically accumulates in Camellia species, especially C. sinensis. Most plants contain the enzyme/gene catalyzing the conversion of ethylamine and l-glutamic acid to l-theanine. After supplementation with [H]ethylamine, all the plants produce [H]l-theanine, which suggests that ethylamine availability is the reason for the difference in l-theanine accumulation between C. sinensis and other plants.

A variety of conditions lead to anemia, which affects one-quarter of the world's population. Previous genome-wide association studies revealed a number of genetic polymorphisms significantly associated with plasma iron status. To evaluate the association of genetic variants in genes involved in iron delivery and hepcidin regulation pathways with the risk of iron-deficiency anemia (IDA), the following single nucleotide polymorphisms were genotyped in 2139 unrelated elderly Chinese women: rs3811647 (TF), rs7385804 (TFR2), rs235756 (BMP2), and rs855791(V736A) and rs4820268 (TMPRSS6, encoding matriptase-2). We identified common variants in TMPRSS6 as being genetic risk factors for both iron deficiency (OR(rs855791) = 1.55, P = 4.96 × 10(-8)) and IDA (OR(rs855791) = 1.78, P = 8.43 × 10(-9)). TMPRSS6 polymorphisms were also associated with lower serum iron (SI) and hemoglobin levels, consistent with their associations to increased iron deficiency and anemia risk. Variants rs3811647 in TF and rs7385804 in TFR2 were associated with reduced SI, serum transferrin and transferrin saturation levels; however, these variants were not associated with iron deficiency or anemia risk. Our findings suggest that TF, TFR2 and TMPRSS6 polymorphisms are significantly associated with decreased iron status, but only variants in TMPRSS6 are genetic risk factors for iron deficiency and IDA.

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L-Theanine is a specialized metabolite in the tea (Camellia sinensis) plant which can constitute over 50% of the total amino acids. This makes an important contribution to tea functionality and quality, but the subcellular location and mechanism of biosynthesis of L-theanine are unclear. Here, we identified five distinct genes potentially capable of synthesizing L-theanine in tea. Using a nonaqueous fractionation method, we determined the subcellular distribution of L-theanine in tea shoots and roots and used transient expression in Nicotiana or Arabidopsis to investigate in vivo functions of L-theanine synthetase and also to determine the subcellular localization of fluorescent-tagged proteins by confocal laser scanning microscopy. In tea root tissue, the cytosol was the main site of L-theanine biosynthesis, and cytosol-located CsTSI was the key L-theanine synthase. In tea shoot tissue, L-theanine biosynthesis occurred mainly in the cytosol and chloroplasts and CsGS1.1 and CsGS2 were most likely the key L-theanine synthases. In addition, L-theanine content and distribution were affected by light in leaf tissue. These results enhance our knowledge of biochemistry and molecular biology of the biosynthesis of functional tea compounds.

Jasmine lactone has a potent odor that contributes to the fruity, sweet floral aroma of tea ( Camellia sinensis). Our previous study demonstrated that jasmine lactone was mostly accumulated at the turnover stage of the oolong tea manufacturing process. This study investigates the previously unknown mechanism of formation of jasmine lactone in tea leaves exposed to multiple stresses occurring during the growth and manufacturing processes. Both continuous mechanical damage and the dual stress of low temperature and mechanical damage enhanced jasmine lactone accumulation in tea leaves. In addition, only one pathway, via hydroperoxy fatty acids from unsaturated fatty acid, including linoleic acid and α-linolenic acid, under the action of lipoxygenases (LOXs), especially CsLOX1, was significantly affected by these stresses. This is the first evidence of the mechanism of jasmine lactone formation in tea leaves and is a characteristic example of plant volatile formation in response to dual stress.

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Insect attack is known to induce a high accumulation of volatile metabolites in tea (Camellia sinensis). However, little information is available concerning the effect of insect attack on tea quality-related nonvolatile specialized metabolites. This study aimed to investigate the formation of characteristic nonvolatile specialized metabolites in tea leaves in response to attack by major tea insects, namely, tea green leafhoppers and tea geometrids, and determine the possible involvement of phytohormones in metabolite formation resulting from insect attack. Both tea green leafhopper and tea geometrid attacks increased the jasmonic acid and salicylic acid contents. The abscisic acid content was only increased under tea green leafhopper attack, perhaps due to special continuous piercing−sucking wounding. Tea green leafhopper attack induced the formation of theaflavins from catechins under the action of polyphenol oxidase, while tea geometrid attack increased the L-theanine content. Exogenous phytohormone treatments can affect the caffeine and catechin contents. These results will help to determine the influence of major tea pest insects on important tea quality-related metabolites and enhance understanding of the relationship of phytohormones and quality-related nonvolatile metabolite formation in tea exposed to tea pest insect attacks.