Search

Abstract: Despite considerable attention paid to Chaohu Lake in China, the dynamics of bacterioplankton community composition (BCC) on spatial and seasonal scales are poorly understood. In this study, water samples were collected from autumn 2006 to summer 2007 at five positions in Chaohu Lake with different trophic status. BCC of these samples was determined by both the PCR amplification of the 16S rDNA gene and the denaturing gradient gel electrophoresis (DGGE). The abundance and diversity of bacterioplankton communities at different sampling positions showed similar seasonal patterns. The BCCs in the samples varied substantially, and the pattern of changes indicated that the seasonal difference might have a significant impact on the BCC’s structure in the lake. Canonical correspondence analysis (CCA) on the DGGE patterns and physicochemical parameters indicated that the temperature and the levels of 5-d biochemical O2 demand (BOD5), NH3–N, CODMn, total nitrogen, total phosphorous, and dissolved oxygen significantly influenced the BCC, and four of the seven variables were related to the level of eutrophication. Our results indicate that eutrophic status and season are the most influential factors in determining BCC in Chaohu Lake. [Copyright &y& Elsevier]

Monoterpenes and sesquiterpenes are the most abundant volatiles in tea plants and have dual functions in aroma quality formation and defense responses in tea plants. Terpene synthases (TPS) are the key enzymes for the synthesis of terpenes in plants; however, the functions of most of them in tea plants are still unknown. In this study, six putative terpene biosynthesis gene clusters were identified from the tea plant genome. Then we cloned three new TPS-b subfamily genes, CsTPS08 , CsTPS10 and CsTPS58. In vitro enzyme assays showed that CsTPS08 and CsTPS58 are two multiple-product terpene synthases, with the former synthesizing linalool as the main product, and β-myrcene, α-phellandrene, α-terpinolene, D-limonene, cis-β-ocimene, trans-β-ocimene and (4E,6Z)-allo-ocimene as minor products are also detected, while the latter catalyzing the formation of α-pinene and D-limonene using GPP as the substrate. No product of CsTPS10 was detected in the prokaryotic expression system, but geraniol production was detected when transiently expressed in tobacco leaves. CsTPS08 and CsTPS10 are two functional members of a monoterpene synthase gene cluster, which were significantly induced during both Ectropis oblique feeding and fresh leaf spreading treatments, suggesting that they have dual functions involved in tea plant pest defense and tea aroma quality regulation. In addition, the differences in their expression levels in different tea plant cultivars provide a possibility for the subsequent screening of tea plant resources with a specific aroma flavor. Our results deepen the understanding of terpenoid synthesis in tea plants. • Six putative terpene gene clusters were identified from the tea plant genome. • CsTPS08 and CsTPS10 are two functional members on a monoterpene synthase gene cluster, and their main enzymatic products are the two most abundant monoterpenes in tea plant leaves, linalool and geraniol, respectively. • The expression levels of CsTPS08 and CsTPS10 were significantly induced during both Ectropis oblique feeding and fresh leaf spreading treatments, suggesting that they have dual functions involved in tea plant pest defense and tea aroma quality regulation. [ABSTRACT FROM AUTHOR]

Alternative splicing (AS) was an important post-transcriptional mechanism that involved in plant resistance to adversity stress. WRKY transcription factors function as transcriptional activators or repressors to modulate plant growth, development and stress response. However, the role of alternate splicing of WRKY in cold tolerance is poorly understood in tea plants. In this study, we found that the CsWRKY21 transcription factor, a member of the WRKY IId subfamily, was induced by low temperature. Subcellular localization and transcriptional activity assays showed that CsWRKY21 localized to the nucleus and had no transcriptional activation activity. Y1H and dual-luciferase reporter assays showed that CsWRKY21 suppressed expression of CsABA8H and CsUGT by binding with their promoters. Transient overexpression of CsABA8H and CsUGT reduced abscisic acid (ABA) content in tobacco leaves. Furthermore, we discovered that CsWRKY21 undergoes AS in the 5′UTR region. The AS transcript CsWRKY21-b was induced at low temperature, up to 6 folds compared to the control, while the full-length CsWRKY21-a transcript did not significantly change. Western blot analysis showed that the retention of introns in the 5′UTR region of CsWRKY21-b led to higher CsWRKY21 protein content. These results revealed that alternative splicing of CsWRKY21 involved in cold tolerance of tea plant by regulating the protein expression level and then regulating the content of ABA, and provide insights into molecular mechanisms of low temperature defense mediated by AS in tea plant. • CsWRKY21 participates in the cold resistance of tea plants by regulating the expression of CsABA8H and CsUDP to regulate ABA content. • The alternative splicing transcript CsWRKY21-b was induced 6 folds compared to the control at low temperature rather than its full-length transcript. • 5′ UTR region retained by introns affect level of protein translation. [ABSTRACT FROM AUTHOR]

• Volatile and non-volatile metabolites were characterized and analyzed. • Different data fusion and feature extraction methods were investigated. • Common dimension was used to analyze block weights and visualize data. • Mid-level data fusion in the RBF-SVM model achieved 93.33% test set accuracy. • HS-SPME-GC–MS and NMR achieved synergy to obtain higher classification accuracy. The narrow geographical traceability of green tea is both important and challenging. This study aimed to establish multi-technology metabolomic and chemometric approaches to finely discriminate the geographic origins of green teas. Taiping Houkui green tea samples were analyzed by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry and 1H NMR of polar (D 2 O) and non-polar (CDCl 3). Common dimension, low-level and mid-level data fusion approaches were tested to verify if the combination of several analytical sources can improve the classification ability of samples from different origins. In assessments of tea from six origins, the single instrument data test set results in 40.00% to 80.00% accuracy. Data fusion improved single-instrument performance classification with mid-level data fusion to obtain 93.33% accuracy in the test set. These results provide comprehensive metabolomic insights into the origin of TPHK fingerprinting and open up new metabolomic approaches for quality control in the tea industry. [ABSTRACT FROM AUTHOR]

Abstract Tea plant is an important economic crop and is vulnerable to drought. A good understanding of tea drought tolerance mechanisms is required for breeding robust drought tolerant tea varieties. Previous studies showed mesophyll cells' ability to maintain K+ is associated with its stress tolerance. Here, in this study, 12 tea varieties were used to investigate the role of mesophyll K+ retention ability towards tea drought stress tolerance. A strong and negative correlation (R2 = 0.8239, P < 0.001) was found between PEG (mimic drought stress)-induced K+ efflux from tea mesophyll cells and overall drought tolerance in 12 tea varieties. In agreement with this, a significantly higher retained leaf K+ content was found in drought tolerant than the sensitive tea varieties. Furthermore, exogenous applied K+ (5 mM) significantly alleviated drought-induced symptom in tea plants, further supporting our finding that mesophyll K+ retention is an important component for drought tolerance mechanisms in tea plants. Moreover, pharmacological experiments showed that the contribution of K+ outward rectifying channels and non-selective cation channels in controlling PEG-induced K+ efflux from mesophylls cells are varied between drought tolerant and sensitive tea varieties. Highlights • Mesophyll K+ retention is an important component for drought tolerance mechanisms in tea plants. • Non-selective cation channels (NSCC) play a major role in controlling K+ efflux from tea leaf mesophyll cells under drought. • The contribution of the K+ selective channels and NSCC channels is varied in tea varieties contrasting in drought tolerancee. [ABSTRACT FROM AUTHOR]

Terpenoid volatiles are major contributors to the floral odors and are responsible for the sensory quality of teas. However, little is known about the global regulation of various networks to achieve high terpenoids production in tea leaves. Here, metabolomics and transcriptome profiles were obtained from the tea leaves harvested in five different months. Our results showed that most sesquiterpene contents were lowest when sampled in April, increased markedly in June, and declined in August, September and October. An opposite accumulation pattern was observed in the majority of monoterpenes, and similar accumulation patterns were shared among a subset of sesquiterpenes and monoterpenes. We further found expression patterns of many genes in MVA pathway strongly correlated with the accumulation of some monoterpenes; as well, expression profiles of MEP pathway genes were closely associated with a few sesquiterpenes. A crosstalk regulatory network was constructed using co-expression analysis, and 13 transcription factors genes, with possible crucial roles in the regulation of terpene metabolism, were uncovered in the network. Additionally, CsOCS2 , one key gene involved in terpenoid biosynthesis was functionally characterized in vitro . These results suggest that there might be crosstalk and competition for substrates between the down-stream monoterpenes and sesquiterpenes biosynthesis, which endow tea with its unique aroma, during different growth months. [ABSTRACT FROM AUTHOR]

Abstract: Tea (Camellia sinensis) is a commercially important crop that contains valuable secondary metabolites. To understand the molecular regulation of secondary metabolism in tea, we selected and analyzed two cell lines of tea callus (Yunjing63Y and Yunjing63X) that showed different morphological characteristics and catechin contents. Yunjing63Y callus was yellow and tight, while yunjing63X callus was white and loose. HPLC analyses showed that Yunjing63Y contained 3.71 times higher levels of catechins than Yunjing63X. Using cDNA amplified fragment-length polymorphism (cDNA-AFLP) we identified 68 genes that were differentially expressed between the two lines. Of the 68 differentially expressed ESTs, 40 showed higher expressions in Yunjing63Y and 28 showed higher expressions in Yunjing63X. BLASTX comparisons classified these ESTs into seven functional groups; phenylpropanoid metabolism (2.9%), UDPG-dependent glucosyl transferase (8.8%), transcription factors (11.8%), transporters (13.2%), signal transduction (19.1%), other metabolism (26.5%), and unknown (17.7%). We used qRT-PCR to validate the expression of genes and ESTs, and found that genes associated with flavan-3-ols biosynthesis and metabolism were expressed at higher levels in Yunjing63Y than in Yunjing63X. In addition, the expression of ESTs associated with flavonoid biosynthesis, regulation and transport were higher in Yunjing63Y than in Yunjing63X. The full-length cDNA of a EST coding for a putative MYB transcription factor was amplified using rapid amplification of cDNA ends (RACE). The resulting 1270bp long cDNA, named CsMYB1, contained a 933-bp ORF encoding a 310-amino acid protein with a predicted molecular weight of 105.27kDa and a predicted isoelectric point of 4.85 and showed highest homology to plant MYBs likely involved in stress signaling. [Copyright &y& Elsevier]

Abstract: Tea (Camellia sinensis (L.) O. Kuntze) is a commercially important crop that is valued for its secondary metabolites. Light is an important environmental parameter that regulates plant growth and development and influences the phenylpropanoid metabolism in plants. To investigate the molecular mechanism by which light regulates phenylpropanoid metabolism, we established light-induced suppression subtractive hybridization (SSH) cDNA libraries of tea calli. A total of 265 clones from the library were selected, sequenced, and analyzed in this study. Nine diverse ESTs involved in phenylpropanoid biosynthesis were detected in the library. A new CsDFR gene (CsDFR2), higher increment of the expression activated by light than the previously reported CsDFR gene (CsDFR1), was cloned. The key phenylpropanoid compounds and representative genes expression analysis implied that light could be effective for activation of the biosynthesis of phenylpropanoids. Compared to the darkness control, levels of lignins, catechins, and PAs were increased 3.46, 3.00, and 1.21-fold, in light-induced calli, respectively. And lignin biosynthesis genes, involved in CCoAOMT, HCT and CCR, were identified in the light-induced SSH library. Therefore it was assumed that lignins might be the main phenylpropanoid metabolites activated by light in tea calli. In addition, our researches found that catechins, as the main secondary metabolites, significantly decreased in the tea calli compared to those in tea mature leaves, While PAs (polymer of catechins) in calli did not decrease compared to mature leaves. The data suggest that polymerization reaction might be the main pathway of flavonoid metabolism in tea callus. The SSH library established in this study represents a valuable resource for better understanding the mechanisms of light-induced secondary metabolism in tea plants. [Copyright &y& Elsevier]

[Display omitted] • VTs and FADVs were the main aroma compounds accumulated in green tea during spreading. • The degree of aroma accumulation promoted by moderate spreading was genotype dependent. • The aroma accumulation induced by spreading mainly derived from de novo synthesis rather than glycoside hydrolysis. • Two co-expression networks highly related to accumulation of aroma compounds were identified. Spreading is an indispensable process in the aroma formation of premium green tea. In this study, volatile metabolomics and transcriptomics were performed for three tea plant cultivars to investigate the mechanism of changes occurring in volatile compounds during green tea spreading. The content of primary aroma compounds significantly increased after spreading, the Wickremasinghe-Yamanishi ratio decreased and the Owuor's flavor index increased with the extension of spreading time, and the degree of aroma production was genotype-dependent. Volatile terpenes and fatty acid-derived volatiles were the principal aroma volatiles that accumulated during the spreading of green tea, and the trends of their changes were consistent with the expression pattern of related synthesis pathway genes, indicating that they were primarily derived from de novo synthesis rather than glycoside hydrolysis. Two co-expression networks that were highly correlated with variations in the volatile component contents during the spreading process were identified via WGCNA. Our results provide insights into spreading that can be considered to improve the quality of green tea. [ABSTRACT FROM AUTHOR]

• Metabolites are identified that affect tea quality during five months. • Flavonoids are major differential metabolites and show specific temporal accumulation patterns. • Flavonoid-related genes expressed specifically that influenced the accumulation of flavonoids. • Structural genes involved in flavonoid biosynthesis are regulated by specific transcription factors. Flavonoids are the major class of characteristic secondary compounds in Camellia sinensis that affect quality of tea. However, the temporal variation and the underlying regulatory mechanism of flavonoid biosynthesis during different growth months require a further investigation. Here, we combined analyses of the metabolomics and transcriptomics to tea leaves freshly collected during five different months for a comprehensive understanding of flavonoid metabolism regulation in tea plants. Through loading plot analysis, significant changes in the contents of metabolites during growing months were discovered, and further co-expression and association analysis indicated that one flavone glycoside (naringenin-7-O-glucoside) and two flavonol glycosides (quercetin-3-O-galactoside and kaemferol-3-O-(6″-O-p-courmaroyl)-glucoside) were evaluated as growth markers, which may explain the high bitterness and astringency of August teas; additionally, the high levels of two flavan-3-ols (gallocatechin and catechin gallate) may contribute to the flavor formation of April tea. Meanwhile, multiple flavonoid-related structural genes, MYB and bHLH transcription factors exhibit specific expression patterns to modulate the biosynthesis of these key flavonoids. A co-expression regulatory sub-network was constructed based on profiles of differentially expressed genes; one CsbHLH and six transcription factors (three CsbHLHs and three CsMYBs) exhibited negative and positive roles in the regulation of flavonoid biosynthetic genes, respectively. Taken together, our results provide new insights into the regulation of principle flavonoids for unique flavor of tea regulated by many flavonoid-related structural genes and transcription factors during different growth months. [ABSTRACT FROM AUTHOR]