Cohort profile: Worldwide Collaboration on OsteoArthritis prediCtion for the Hip (World COACH) - an international consortium of prospective cohort studies with individual participant data on hip osteoarthritis.

PURPOSE: Hip osteoarthritis (OA) is a major cause of pain and disability worldwide. Lack of effective therapies may reflect poor knowledge on its aetiology and risk factors, and result in the management of end-stage hip OA with costly joint replacement. The Worldwide Collaboration on OsteoArthritis prediCtion for the Hip (World COACH) consortium was established to pool and harmonise individual participant data from prospective cohort studies. The consortium aims to better understand determinants and risk factors for the development and progression of hip OA, to optimise and automate methods for (imaging) analysis, and to develop a personalised prediction model for hip OA. PARTICIPANTS: World COACH aimed to include participants of prospective cohort studies with ≥200 participants, that have hip imaging data available from at least 2 time points at least 4 years apart. All individual participant data, including clinical data, imaging (data), biochemical markers, questionnaires and genetic data, were collected and pooled into a single, individual-level database. FINDINGS TO DATE: World COACH currently consists of 9 cohorts, with 38 021 participants aged 18-80 years at baseline. Overall, 71% of the participants were women and mean baseline age was 65.3±8.6 years. Over 34 000 participants had baseline pelvic radiographs available, and over 22 000 had an additional pelvic radiograph after 8-12 years of follow-up. Even longer radiographic follow-up (15-25 years) is available for over 6000 of these participants. FUTURE PLANS: The World COACH consortium offers unique opportunities for studies on the relationship between determinants/risk factors and the development or progression of hip OA, by using harmonised data on clinical findings, imaging, biomarkers, genetics and lifestyle. This provides a unique opportunity to develop a personalised hip OA risk prediction model and to optimise methods for imaging analysis of the hip.

Cam morphology is strongly and consistently associated with development of radiographic hip osteoarthritis throughout 4 follow-up visits within 10 years.

OBJECTIVE: To determine the association between cam morphology and the development of radiographic hip osteoarthritis (RHOA) at four time points within 10-year follow-up. DESIGN: The nationwide prospective Cohort Hip and Cohort Knee study includes 1002 participants aged 45-65 years with 2-, 5-, 8-, and 10-year follow-ups. The associations of cam morphology (alpha angle >60°) and large cam morphology (alpha angle >78°) in hips free of osteoarthritis at baseline (Kellgren & Lawrence (KL) grade <2) with the development of both incident RHOA (KL grade≥2) and end-stage RHOA (KL grade≥3) were estimated using logistic regression with generalized estimating equation at each follow-up and using Cox regression over 10 years, adjusted for age, sex, and body mass index. RESULTS: Both cam morphology and large cam morphology were associated with the development of incident RHOA at all follow-ups with adjusted Odd Ratios (aORs) ranging from 2.7 (95% Confidence interval 1.8-4.1) to 2.9 (95% CI 2.0-4.4) for cam morphology and ranging from 2.5 (95% CI 1.5-4.3) to 4.2 (95% CI 2.2-8.3) for large cam morphology. For end-stage RHOA, cam morphology resulted in aORs ranging from 4.9 (95% CI 1.8-13.2) to 8.5 (95% CI 1.1-64.4), and aORs for large cam morphology ranged from 6.7 (95% CI 3.1-14.7) to 12.7 (95% CI 1.9-84.4). CONCLUSIONS: Cam morphology poses the hip at 2-13 times increased odds for developing RHOA within a 10-year follow-up. The association was particularly strong for large cam morphology and end-stage RHOA, while the strength of association was consistent over time.

Characterization of Key Odorants in Lingtou Dancong Oolong Tea and Their Differences Induced by Environmental Conditions from Different Altitudes.

Lingtou Dancong oolong tea is a famous Chinese oolong tea due to its special honey-like aroma. However, little is known about its specific aroma profile and key contributors. Furthermore, whether the aroma characteristics of Lingtou Dancong oolong tea are affected by the environmental conditions at different altitudes is unknown. In this study, the aromas in Lingtou Dancong oolong tea were extracted and analyzed by stir-bar sorptive extraction (SBSE) combined with gas chromatography-olfactometry (GC-O) and GC-mass spectrometry (GC-MS), and the aroma profiles of tea plants grown at different altitudes were compared. We detected 59 odor compounds in Lingtou Dancong oolong tea. Eight compounds with honey and floral odors were identified as key components on the basis of GC-O, GC-MS, odor activity value, and flavor dilution analyses. Differences in the contents of precursor geranyl diphosphate and transcript levels of structural genes were found to be responsible for the differential accumulation of linalool and hotrienol among plants grown at different altitudes. This is the first report on the aroma characteristics and key contributors of Lingtou Dancong oolong tea and their differences, as affected by altitude. These results provide details of the chemical basis of the aroma quality of Lingtou Dancong oolong tea.

Effects of temperature and light on quality-related metabolites in tea [Camellia sinensis (L.) Kuntze] leaves.

In China, the environmental conditions in mountainous regions are suitable for producing high-quality tea, but the underlying mechanism is unknown. Analyses of published data revealed tea leaves harvested at high altitudes are associated with high-quality tea, possibly because of the effects of light and temperature. This was confirmed by simulating the changes induced by temperature and light at different altitudes. Catechin biosynthesis was inhibited by high altitudes, whereas free amino acid contents increased, leading to a decrease in polyphenol to amino acids ratio. Under simulated high-altitude conditions, increases in the abundance of l-theanine and other amino acids were due to the increase in precursor contents and chloroplast protein hydrolysis, respectively. In addition, some aroma compound contents increased in fresh or wounded leaves because of up-regulated expression of key structural genes. Overall, tea taste and aroma were enhanced by simulated high-altitude conditions. This study provides the basis for enhancing low-quality tea raw materials.

Characterizing the cultivar-specific mechanisms underlying the accumulation of quality-related metabolites in specific Chinese tea (Camellia sinensis) germplasms to diversify tea products.

The diverse tea (Camellia sinensis) germplasms in China include those that specifically accumulate metabolites, such as anthocyanin, catechin, amino acid, caffeine, aroma compound, and chlorophyll. There is interest in the derived products because of special flavor quality or high efficacy activity. This review describes the characteristics of specific tea germplasms and associated regulatory mechanisms. High expression levels of the corresponding biosynthetic genes lead to the substantial accumulation of anthocyanins. The increased metabolic flux from anthocyanins to galloylated catechins is responsible for the occurrence of high-catechin germplasms. The precursor ethylamine determines the differential abundance of l-theanine between tea and other plants. The high amino acid contents in albino germplasms are the result of decreased l-theanine hydrolysis. In low-caffeine tea germplasms, caffeine synthase genes are minimally expressed or mutated. High-aroma germplasms are associated with an increase in the precursors or strong stress-induced responses. Enhanced chloroplast and chlorophyll synthesis is a hallmark of the high-chlorophyll germplasms. Overall, biosynthetic metabolism might have contributed to the occurrence of specific tea germplasms. Furthermore, elucidation the deeper molecular mechanisms in specific tea germplasms are significant and urgent. The information will enhance our understanding of the metabolic activities in tea plants, with implications for tea breeding.

Mechanism underlying the carotenoid accumulation in shaded tea leaves.

Carotenoids contribute to tea leaf coloration and are the precursors of important aromatic compounds. Shading can promote the accumulation of carotenoids in tea leaves, but the underlying mechanism remains unknown. In the study, we analyzed the content and composition of carotenoids, and transcript levels and functions of related genes in carotenoid biosynthesis using HPLC, qRT-PCR, and heterologous expression system. It was found that long-term shading (14 days, 90% shading) significantly increased the total carotenoid content in tea leaves, and increased the expression of non-mevalonate pathway (MEP) genes (CsDXS1 and CsDXS3) and key genes in carotenoid synthesis pathway (CsPSY, CsLCYB, and CsLCYE). Long-term exposure to darkness (14 days, 0 lx) decreased the transcription of most carotenoid biosynthetic genes and adversely affected carotenoid accumulation. Furthermore, CsDXS1, CsDXS3, CsPSY, CsLCYB, and CsLCYE were functionally identified and contributed to the enhanced accumulation of carotenoids in tea leaves in response to long-term shading.

Soil nutrient deficiency decreases the postharvest quality-related metabolite contents of tea (Camellia sinensis (L.) Kuntze) leaves.

The long-term cultivation of tea plants without fertilization can severely decrease yield, but it remains unclear whether this soil nutrient deficiency affects tea quality. In this study, tea plants (Camellia sinensis (L.) Kuntze) cultivated in unfertilized soil for 11 years were analyzed. The soil nutrient deficiency down-regulated protochlorophyllide oxidoreductase-encoding gene expression, which adversely affected chlorophyll biosynthesis, ultimately leading to leaf etiolation. Because of decreased synthesis and increased degradation in response to nutrient deficiency, l-theanine content decreased to 11.4% of the control level, which increased the phenol-ammonia ratio and decreased taste quality. Soil nutrient deficiency also decreased the abundance of many aroma compounds (e.g., green leaf volatile, linalool and its oxides, and methyl salicylate). Thus, nutrient deficiency adversely influences tea color, taste, and aroma. This study provides researchers and tea growers with important information regarding the effects of soil nutrient deficiency on tea quality and the rational fertilization of tea gardens.

Mechanism Underlying the Shading-Induced Chlorophyll Accumulation in Tea Leaves.

Besides aroma and taste, the color of dry tea leaves, tea infusion, and infused tea leaves is also an important index for tea quality. Shading can significantly increase the chlorophyll content of tea leaves, leading to enhanced tea leaf coloration. However, the underlying regulatory mechanism remains unclear. In this study, we revealed that the expressions of chlorophyll synthesis genes were significantly induced by shading, specially, the gene encoding protochlorophyllide oxidoreductase (CsPOR). Indoor control experiment showed that decreased light intensity could significantly induce the expression of CsPOR, and thus cause the increase of chlorophyll content. Subsequently, we explored the light signaling pathway transcription factors regulating chlorophyll synthesis, including CsPIFs and CsHY5. Through expression level and subcellular localization analysis, we found that CsPIF3-2, CsPIF7-1, and CsHY5 may be candidate transcriptional regulators. Transcriptional activation experiments proved that CsHY5 inhibits CsPORL-2 transcription. In summary, we concluded that shading might promote the expression of CsPORL-2 by inhibiting the expression of CsHY5, leading to high accumulation of chlorophyll in tea leaves. The results of this study provide insights into the mechanism regulating the improvements to tea plant quality caused by shading.

Effects of Long-Term Non-Pruning on Main Quality Constituents in 'Dancong' Tea (Camellia sinensis) Leaves Based on Proteomics and Metabolomics Analysis.

'Dancong' tea is a famous traditional Oolong tea. In order to keep the original taste of "ancient tea trees", most of the 'Dancong' tea plants are planted in a single plant pattern without pruning. The objective of this study was to explore the effects of long-term non-pruning on main quality constituents in 'Dancong' tea. The results showed that the contents of free amino acids, chlorophylls, and floral-honey aromatic substances in tea leaves of unpruned tea plants were higher than those in every year pruned tea plants, while the catechin content in leaves of pruned tea plants was higher than that in leaves of unpruned tea plants. Quantitative proteomics analysis showed that most enzymes involved in biosynthesis of catechins were downregulated in leaves of unpruned tea plants. Five proteins involved in chlorophyll metabolism and 12 proteins related to photosynthesis were upregulated, and the results suggested that higher chlorophyll content and more efficient photosynthetic energy conversion may be important for the higher accumulation of special quality components in leaves of unpruned tea plants. The findings of this study will advance our understanding of the mechanism of formation of different metabolites in leaves of unpruned and pruned tea plants.

Elucidation of the Regular Emission Mechanism of Volatile ß-Ocimene with Anti-insect Function from Tea Plants (Camellia sinensis) Exposed to Herbivore Attack.

Herbivore-induced plant volatiles (HIPVs) play an important role in insect resistance. As a common HIPV in tea plants (Camellia sinensis), ß-ocimene has shown anti-insect function in other plants. However, whether ß-ocimene in tea plants also provides insect resistance, and its mechanism of synthesis and emission are unknown. In this study, ß-ocimene was confirmed to interfere with tea geometrid growth via signaling. Light was identified as the key factor controlling regular emission of ß-ocimene induced by the wounding from tea geometrids. ß-Ocimene synthase (CsBOS1) was located in plastids and catalyzed ß-ocimene formation in overexpressed tobacco. CsBOS1 expression in tea leaves attacked by tea geometrids showed a day-low and night-high variation pattern, while CsABCG expression involved in volatile emission showed the opposite pattern. These two genes might regulate the regular ß-ocimene emission from tea plants induced by tea geometrid attack. This study advances the understanding on HIPV emission and signaling in tea plants.

Transformation of Salicylic Acid and Its Distribution in Tea Plants (Camellia sinensis) at the Tissue and Subcellular Levels.

Salicylic acid (SA) is a well-known immune-related hormone that has been well studied in model plants. However, less attention has been paid to the presence of SA and its derivatives in economic plants, such as tea plants (Camellia sinensis). This study showed that tea plants were rich in SA and responded differently to different pathogens. Feeding experiments in tea tissues further confirmed the transformation of SA into salicylic acid 2-O-ß-glucoside (SAG) and methyl salicylate. Nonaqueous fractionation techniques confirmed that SA and SAG were mostly distributed in the cytosol of tea leaves, consistent with distributions in other plant species. Furthermore, the stem epidermis contained more SA than the stem core both in C. sinensis cv. "Jinxuan" (small-leaf species) and "Yinghong No. 9" (large-leaf species). Compared with cv. "Yinghong No. 9", cv. "Jinxuan" contained more SAG in the stem epidermis, which might explain its lower incidence rate of wilt disease. This information will improve understanding of SA occurrence in tea plants and provide a basis for investigating the relationship between SA and disease resistance in tea plants.

Uncovering reasons for differential accumulation of linalool in tea cultivars with different leaf area.

It is generally proposed that tea cultivars with larger leaves contain more linalool, an important tea aroma contributor, than ones with smaller leaves. The objective of this study was to confirm the trait and explore the involved reason. Investigation on ten tea cultivars with different leaf areas demonstrated a significant positive correlation between linalool content and leaf area (R2 = 0.739, p = 0.010). Analysis of metabolite and gene expression level showed that the transform ability of linalool into linalool oxides was the key factor. Feeding experiments that supplied tea leaves of different leaf areas with [2H3]linalool under different light conditions revealed that the larger tea leaves receive more light and are less capable of transformation of linalool to linalool oxides, thus leading to linalool accumulation. This information will advance understanding of the variation of linalool content in tea varieties and will provide assistance in breeding and screening of high-linalool tea cultivars.

Enzymatic Reaction-Related Protein Degradation and Proteinaceous Amino Acid Metabolism during the Black Tea (Camellia sinensis) Manufacturing Process.

Amino acids contribute to the nutritional value and quality of black tea. Fermentation is the most important stage of the black tea manufacturing process. In this study, we investigated protein degradation and proteinaceous amino acid metabolism associated with enzymatic reactions during fermentation in the black tea manufacturing process. The results showed that the concentrations of both protein and free amino acids decreased during fermentation. We also confirmed that proteins were broken down into free amino acids by artificially synthesized dipeptide benzyloxycarbonyl glutamyl-tyrosine (Z-Glu-Tyr). Metabolites of the amino acid metabolic pathway increased significantly during fermentation. Furthermore, we confirmed that free amino acids were degraded to volatile compounds in a tracer experiment with the isotope precursor. These results provide information that will help black tea manufacturers improve the quality of black tea.

Correction: Insects (Thrips hawaiiensis (Morgan)) change the stereochemical configuration of 1-phenylethanol emitted from tea (Camellia sinensis) flowers.

[This corrects the article DOI: 10.1039/C7RA03219F.].

Formation of α-Farnesene in Tea (Camellia sinensis) Leaves Induced by Herbivore-Derived Wounding and Its Effect on Neighboring Tea Plants.

Herbivore-induced plant volatiles (HIPVs) play important ecological roles in defense against stresses. In contrast to model plants, reports on HIPV formation and function in crops are limited. Tea (Camellia sinensis) is an important crop in China. α-Farnesene is a common HIPV produced in tea plants in response to different herbivore attacks. In this study, a C. sinensis α-farnesene synthase (CsAFS) was isolated, cloned, sequenced, and functionally characterized. The CsAFS recombinant protein produced in Escherichia coli was able to transform farnesyl diphosphate (FPP) into α-farnesene and also convert geranyl diphosphate (GPP) to ß-ocimene in vitro. Furthermore, transient expression analysis in Nicotiana benthamiana plants indicated that CsAFS was located in the cytoplasm and could convert FPP to α-farnesene in plants. Wounding, to simulate herbivore damage, activated jasmonic acid (JA) formation, which significantly enhanced the CsAFS expression level and α-farnesene content. This suggested that herbivore-derived wounding induced α-farnesene formation in tea leaves. Furthermore, the emitted α-farnesene might act as a signal to activate antibacterial-related factors in neighboring undamaged tea leaves. This research advances our understanding of the formation and signaling roles of common HIPVs in crops such as tea plants.

Effect of Major Tea Insect Attack on Formation of Quality-Related Nonvolatile Specialized Metabolites in Tea ( Camellia sinensis) Leaves.

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.

Influence of Chloroplast Defects on Formation of Jasmonic Acid and Characteristic Aroma Compounds in Tea (Camellia sinensis) Leaves Exposed to Postharvest Stresses.

Characteristic aroma formation in tea (Camellia sinensis) leaves during the oolong tea manufacturing process might result from the defense responses of tea leaves against these various stresses, which involves upregulation of the upstream signal phytohormones related to leaf chloroplasts, such as jasmonic acid (JA). Whether chloroplast changes affect the formation of JA and characteristic aroma compounds in tea leaves exposed to stresses is unknown. In tea germplasms, albino-induced yellow tea leaves have defects in chloroplast ultrastructure and composition. Herein, we have compared the differential responses of phytohormone and characteristic aroma compound formation in normal green and albino-induced yellow tea leaves exposed to continuous wounding stress, which is the main stress in oolong tea manufacture. In contrast to single wounding stress (from picking, as a control), continuous wounding stress can upregulate the expression of CsMYC2, a key transcription factor of JA signaling, and activate the synthesis of JA and characteristic aroma compounds in both normal tea leaves (normal chloroplasts) and albino tea leaves (chloroplast defects). Chloroplast defects had no significant effect on the expression levels of CsMYC2 and JA synthesis-related genes in response to continuous wounding stress, but reduced the increase in JA content in response to continuous wounding stress. Furthermore, chloroplast defects reduced the increase in volatile fatty acid derivatives, including jasmine lactone and green leaf volatile contents, in response to continuous wounding stress. Overall, the formation of metabolites derived from fatty acids, such as JA, jasmine lactone, and green leaf volatiles in tea leaves, in response to continuous wounding stress, was affected by chloroplast defects. This information will improve understanding of the relationship of the stress responses of JA and aroma compound formation with chloroplast changes in tea.

Habitat management as a safe and effective approach for improving yield and quality of tea (Camellia sinensis) leaves.

Tea (Camellia sinensis) leaves are used to make the most widely consumed beverage globally after water. Therefore, the safety and quality of raw tea leaves are important indices for making tea and related products. Habitat management has been widely used as an environmentally friendly method to control pests in agroecosystems. To investigate the impact of habitat management on tea plantation ecosystems, a habitat management approach with intercropping was established. The function of habitat management on pest control was evaluated. Furthermore, metabolome and transcriptome analysis were applied to assay changes in quality-related metabolites. The habitat management approach was found to maintain arthropod biodiversity and develop natural arthropod enemies in the tea plantation. Therefore, the yield of the habitat management-treated tea plantation was increased. Metabolome analysis showed that epigallocatechin-3-gallate, the major catechin in tea leaves, has a significantly increased content in leaves of tea plants under habitat management compared with those in the control tea plantation. The content of L-theanine, the major amino acid in tea leaves, was not significantly changed in tea plants under habitat management. Furthermore, aroma compounds were more abundant in tea leaves from the habitat management-treated tea plantation than those from the chemical pesticide-treated tea plantation. Therefore, habitat management is reported for the first time as a safe and effective approach to improving the yield and quality of tea leaves.

Differential accumulation of specialized metabolite l-theanine in green and albino-induced yellow tea (Camellia sinensis) leaves.

l-Theanine is a specialized metabolite in tea (Camellia sinensis) leaves that contributes to tea function and quality. Yellow tea leaves (albino) generally have higher l-theanine contents than green tea leaves (normal), but the reason is unknown. The objective of this study was to investigate why l-theanine is accumulated in yellow tea leaves. We compared original normal leaves (green) and light-sensitive albino leaves (yellow) of cv. Yinghong No. 9. The l-theanine content was significantly higher in yellow leaves than in green leaves (p ≤ 0.01). After supplementation with [2H5]-l-theanine, yellow leaves catabolized less [2H5]-l-theanine than green leaves (p ≤ 0.05). Furthermore, most plants contained the enzyme catalyzing l-theanine conversion to ethylamine and l-glutamic acid. In conclusion, l-theanine accumulation in albino-induced yellow tea leaves was due to weak l-theanine catabolism. The differential accumulation mechanism differed from the l-theanine accumulation mechanism in tea and other plants.

Differential Accumulation of Aroma Compounds in Normal Green and Albino-Induced Yellow Tea (Camellia sinensis) Leaves.

Tea (Camellia sinensis) cultivars with green leaves are the most widely used for making tea. Recently, tea mutants with white or yellow young shoots have attracted increasing interest as raw materials for making "high-quality" tea products. Albino teas are generallycharacterized as having metabolites of relatively high amino acid content and lower catechin content. However, little is known about aroma compounds in albino tea leaves. Herein, we compared original normal leaves (green) and light-sensitive albino leaves (yellow) of cv. Yinghong No. 9. GC-MS was employed to analyze endogenous tea aroma compounds and related precursors. Quantitative real time PCR was used to measure expression levels of genes involved in biosyntheses of tea aromas.The total contents of most endogenous free tea aromas, including aroma fatty acid derivatives, aroma terpenes, and aroma phenylpropanoids/benzenoids, and their glycosidically bound aroma compounds, were lower in yellow leaves than in green leaves. The content of the key precursor geranyl diphosphate (GDP) and expression levels of key synthetic genes involved in the formation of linalool, a major aroma compound in cv. Yinghong No. 9, were investigated. Linalool content was lower in albino-induced yellow leaves, which was due to the lower GDP content compared with normal green leaves.