Melatonin-mediated regulation of anthocyanin biosynthesis and antioxidant defense confer tolerance to arsenic stress in Camellia sinensis L.

Arsenic is a toxic metalloid for both animals and plants. The signaling molecule melatonin can enhance abiotic stress tolerance, but the effects of As and melatonin on tea plants and the mechanisms of resilience remain unclear. Here we report that excess As causes severe oxidative stress in tea leaves as revealed by significantly reduced maximal photochemical efficiency of photosystem-II, and increased reactive oxygen species accumulation and lipid peroxidation. However, exogenous melatonin application alleviated the As phytotoxicity and increased the anthocyanin content upto 69.4 % by selectively upregulating the expression of its biosynthetic genes such as CsCHS and CsANS. Comparison of As tolerance between two tea genotypes differing in basal levels of anthocyanin revealed that a tea cultivar with increased anthocyanin content, Zijuan (ZJ), showed enhanced tolerance to As stress compared with Longjing 43 (LJ43) that contained relatively low levels of anthocyanin. Interestingly, exogenous anthocyanin also enhanced As tolerance in LJ43, but exogenous melatonin did not improve As tolerance in ZJ genotype. Analysis of As content in tea leaves revealed that melatonin significantly reduced As content in LJ43 but not in ZJ, suggesting that melatonin-enhanced tolerance to As stress is largely dependent on the basal levels of anthocyanin in tea plants.

Exogenous melatonin improves tea quality under moderate high temperatures by increasing epigallocatechin-3-gallate and theanine biosynthesis in Camellia sinensis L.

Global warming has multifarious effects on crop growth and productivity. Nonetheless, the effects of moderate-high temperatures and melatonin on tea yield and quality remain unclear. In this study, we found that melatonin, a universal growth stimulatory molecule, not only promotes photosynthesis and biomass accumulation in tea plants (Camellia sinensis L.) but also improves tea quality under sub high temperature (SHT). SHT increased the dry biomass and photosynthesis by 40.8% and 28.1%, respectively, and exogenous melatonin caused a further improvement. Moreover, SHT increased the total polyphenol concentrations and decreased the free amino acid concentrations, leading to a significant increase (68.2%) in polyphenol to free amino acid ratio. However, melatonin decreased the polyphenol to free amino acid ratio by delicately improving the concentrations of polyphenols and amino acids. Consistent with the total polyphenol, melatonin increased the concentrations of (-)-catechin, (-)-gallocatechin (GC), and (-)-epigallocatechin-3-gallate (EGCG) in tea leaves. The qRT-PCR analysis revealed that melatonin increased the transcript levels of catechins biosynthesis genes, such as CsCHS, CsCH1, CsF3H, CsDFR, CsANS, CsLAR, and CsANR under SHT. Meanwhile, the theanine concentration was decreased by SHT, which was attributed to the attenuated expression of CsGS, CsGOGAT, CsGDH, and CsTS1. Nonetheless, melatonin significantly increased those transcripts and the content of theanine under SHT. Melatonin also increased the caffeine content by inducing the expression of CsTIDH, CssAMS, and CsTCS1. These results suggest that melatonin could positively alter tea growth and quality by modulating the photosynthesis and biosynthesis of polyphenols, amino acids, and caffeine in tea leaves under SHT.

Mitochondrial COI and 16sRNA evidence for a single species hypothesis of E. vitis, J. formosana and E. onukii in East Asia.

Tea green leafhopper is one of the most damaging tea pests in main tea production regions of East Asia. For lack of recognized morphological characters, the dominant species of tea green leafhoppers in Mainland China, Taiwan and Japan have always been named as Empoasca vitis Göthe, Jacobiasca formosana Paoli and Empoasca onukii MATSUDA, respectively. Furthermore, nothing is known about the genetic relationships among them. In this study, we collected six populations from Mainland China, four populations from Japan and one population from Taiwan, and examined the genetic distances in the COI and 16sRNA regions of mtDNA among them. The results showed that the genetic distances based on single gene or the combined sequences among eleven leafhopper populations were 0.3-1.2%, which were all less than the species boundary of 2%. Moreover, there were at least two haplotypes shared by two distinct populations from different regions. The phylogenetic analysis based on single gene or combined sets also supported that tea green leafhoppers from Mainland China, Taiwan and Japan were closely related to each other, and there were at least two specimens from different regions clustered ahead of those from the same region. Therefore, we propose that the view of recognizing the dominant species of tea green leafhoppers in three adjacent tea production regions of East Asia as different species is unreliable or questionable and suggest that they are a single species.

Detecting deep divergence in seventeen populations of tea geometrid (Ectropis obliqua Prout) in China by COI mtDNA and cross-breeding.

The tea geometrid (Ectropis obliqua Prout, Lepidoptera: Geometridae) is a dominant chewing insect endemic in most tea-growing areas in China. Recently some E. obliqua populations have been found to be resistant to the nucleopolyhedrovirus (EoNPV), a host-specific virus that has so far been found only in E. obliqua. Although the resistant populations are morphologically indistinguishable from susceptible populations, we conducted a nationwide collection and examined the genetic divergence in the COI region of the mtDNA in E. obliqua. Phylogenetic analyses of mtDNA in 17 populations revealed two divergent clades with genetic distance greater than 3.7% between clades and less than 0.7% within clades. Therefore, we suggest that E. obliqua falls into two distinct groups. Further inheritance analyses using reciprocal single-pair mating showed an abnormal F1 generation with an unbalanced sex ratio and the inability to produce fertile eggs (or any eggs) through F1 self-crossing. These data revealed a potential cryptic species complex with deep divergence and reproductive isolation within E. obliqua. Uneven distribution of the groups suggests a possible geographic effect on the divergence. Future investigations will be conducted to examine whether EoNPV selection or other factors prompted the evolution of resistance.

Cloning of a new glutathione peroxidase gene from tea plant (Camellia sinensis) and expression analysis under biotic and abiotic stresses.

BACKGROUND: Tea plant, Camellia sinensis (L.) O. Kuntze, a well-known heavy metal hyperaccumulator, possesses a powerful tolerance to heavy metals. The heavy metal stresses lead to reactive oxygen species (ROS) production, and high concentration of ROS is harmful to plants. The glutathione peroxidase gene has positive function to damage induced by ROS. To understand the mechanism of tolerance to deferent stresses in tea plant, a new glutathione peroxidase gene of tea plant was cloned and its expression pattern was analyzed under abiotic and biotic stresses. RESULTS: A novel cDNA encoding glutathione peroxidase of tea plant (Camellia sinensis) was isolated by rapid amplification of cDNA ends (RACE) method and designated as CsGPX2 (GenBank Accession No. JQ247186). This full-length sequence was 917 nucleotides including a 510 bp open reading frame (ORF), which encoded a polypeptide of 169 amino acids. The deduced amino acid sequence showed high homology with glutathione peroxidases of angiosperms and contained the characteristic conserved motifs of ILAFPCNQF and FTVKD, the highest level of similarity was 85% to a glutathione peroxidase from Ricinus communis (Accession NO. XP_002509790.1). Tissue expression pattern analysis indicated that CsGPX2 expressed similarly in root, stem, leaf and flower of tea plant. The CsGPX2 gene showed strong responses to most abiotic stresses including salinity, heavy metal toxicity, drought, heat, plant hormones, but could not be induced by biotic treatment. CONCLUSIONS: The result suggested that CsGPX2 had potential function in protecting tea plant from peroxidative damage induced by some abiotic stresses.

Intrinsic fiber-optic Fabry-Perot interferometer based on arc discharge and single-mode fiber.

We propose a simple intrinsic Fabry-Perot interferometer (FPI) based on single-mode fiber, where a thin film is formed by arc discharge to serve as one mirror of the FPI cavity. The temperature and refractive-index (RI) characteristics of the proposed device are investigated. Experimental results show that the device can provide temperature-independent measurement of RI with a fringe-contrast sensitivity of ~72.59 dB/RIU (RI units). Meanwhile, it can also be used as a temperature sensor with a wavelength sensitivity of ~8 pm/°C. Therefore, the potential simultaneous measurement of RI and temperature could be realized by detecting the variations of fringe contrast and wavelength, respectively.