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Insect‐induced plant volatile organic compounds (VOCs) may function as either direct defence molecules to deter insects or indirect defence signals to attract the natural enemies of the invading insects. Tea (Camellia sinensis L.), an important leaf‐based beverage crop, is mainly infested by Ectropis obliqua which causes the most serious damage. Here, we report a mechanistic investigation of tea plant‐derived VOCs in an indirect defence mechanism against E. obliqua. Parasitoid wasp Parapanteles hyposidrae, a natural enemy of E. obliqua, showed strong electrophysiological response and selection behaviour towards S‐linalool and β‐ocimene, two monoterpenes with elevated emission from E. obliqua‐damaged tea plants. Larvae frass of E. obliqua, which also released S‐linalool and β‐ocimene, was found to attract both mated female or male Pa. hyposidrae according to gas chromatography‐electroantennogram detection and Y‐tube olfactometer assays. In a field setting, both S‐linalool and β‐ocimene were effective in recruiting both female and male Pa. hyposidrae wasps. To understand the molecular mechanism of monoterpenes‐mediated indirect defence in tea plants, two novel monoterpene synthase genes, CsLIS and CsOCS‐SCZ, involved in the biosynthesis of S‐linalool or β‐ocimene, respectively, were identified and biochemically characterised. When the expression of these two genes in tea plants was inhibited by antisense oligodeoxynucleotide, both volatile emission and attraction of wasps were reduced. Furthermore, gene expression analysis suggested that the expression of CsLIS and CsOCS‐SCZ is regulated by the jasmonic acid signalling pathway in the tea plant. Summary statement: S‐linalool and β‐ocimene elevated emission from Ectropis obliqua‐damaged tea plants. The two monoterpenes were key chemical cues, aroused parasitoid wasp Parapanteles hyposidrae, a dominant natural enemy of E. obliqua, strong electrophysiological response, selection behaviour, and aggregated the wasp in the field. Two novel Terpene synthases CsLIS and CsOCS‐SCZ, involved in the biosynthesis of S‐linalool and β‐ocimene were identified, when they were inhibited in tea plants by antisense oligonucleotides, both volatile emission and attraction of wasps were reduced. [ABSTRACT FROM AUTHOR]

The tea plant is an important economic crop and is widely cultivated. Isopentenyl transferase (IPT) is the first and rate-limiting enzyme of cytokinin (CK) signaling, which plays key roles in plant development and abiotic stress. However, the IPT gene family in tea plants has not been systematically investigated until now. The phylogenetic analyses, gene structures, and conserved domains were predicted here. The results showed that a total of 13 CsIPT members were identified from a tea plant genome database and phylogenetically classified into four groups. Furthermore, 10 CsIPT members belonged to plant ADP/ATP-IPT genes, and 3 CsIPTs were tRNA-IPT genes. There is a conserved putative ATP/GTP-binding site (P-loop motif) in all the CsIPT sequences. Based on publicly available transcriptome data as well as through RNA-seq and qRT-PCR analysis, the CsIPT genes which play key roles in the development of different tissues were identified, respectively. Furthermore, CsIPT6.2 may be involved in the response to different light treatments. CsIPT6.4 may play a key role during the dormancy and flush of the lateral buds. CsIPT5.1 may play important regulatory roles during the development of the lateral bud, leaf, and flower. CsIPT5.2 and CsIPT6.2 may both play key roles for increased resistance to cold-stress, whereas CsIPT3.2 may play a key role in improving resistance to high-temperature stress as well as drought-stress and rewatering. This study could provide a reference for further studies of CsIPT family's functions and could contribute to tea molecular breeding. [ABSTRACT FROM AUTHOR]

Simple Summary: Tritrophic interactions have achieved much attention in research on ecology. The tea plant Camellia sinensis (L.) O. Kuntze is a major economic crop in Asian countries, especially in China. Tea plants suffer infestations from herbivory attack during their lifetime. The tea green leafhopper (Empoasca onukii Matsuda) is a major pest for tea plants. The parasitic or predatory natural enemies of tea green leafhoppers (TGLs) can feed on their eggs, nymphs, or adults. However, a detailed mathematical model for tea plants–TGLs–natural enemies is still lacking. In the current work, we established a novel model based on laboratory measurements or field observations with temperature-dependent effects on tritrophic interactions for tea ecosystems. As expected, cyclic behaviors are identified. Stochastic simulations further showed two TGL outbreaks, the timing of which is consistent with field observations. Effective accumulated temperature (EAT) is possibly an important predictor of TGL outbreak. Applying slow-releasing semiochemicals as either repellents or attractants may be highly efficacious for pest biocontrol. An optimal treatment time of semiochemicals can also be determined. Our detailed model identifies key features of tritrophic interactions involving tea plants and can be extended to other ecosystems. The tea green leaf hopper, Empoasca onukii Matsuda, is a severe pest of tea plants. Volatile emissions from tea shoots infested by the tea green leafhopper may directly repel insect feeding or attract natural enemies. Many studies have been conducted on various aspects of the tritrophic relationship involving tea plants, tea green leafhoppers and natural enemies. However, mathematic models which could explain the dynamic mechanisms of this tritrophic interaction are still lacking. In the current work, we constructed a realistic and stochastic model with temperature-dependent features to characterize the tritrophic interactions in the tea agroecosystem. Model outputs showed that two leafhopper outbreaks occur in a year, with their features being consistent with field observations. Simulations showed that daily average effective accumulated temperature (EAT) might be an important metric for outbreak prediction. We also showed that application of slow-releasing semiochemicals, as either repellents or attractants, may be highly efficacious for pest biocontrol and can significantly increase tea yields. Furthermore, the start date of applying semiochemicals can be optimized to effectively increase tea yields. The current model qualitatively characterizes key features of the tritrophic interactions and provides critical insight into pest control in tea ecosystems. [ABSTRACT FROM AUTHOR]

Tea contains high quantities and diverse types of triterpenoids, particularly in the form of saponins. However, little is yet known about the molecular basis of triterpenoid biosynthesis in tea plant. Here we report on isolation and functional analysis of squalene synthase (SQS) gene from tea plant (Camellia sinensis var. sinensis), which controls the biosynthesis of triterpenoids precursor. First, a full-length cDNA of squalene synthase, designated CsSQS , was isolated from tea plant. The protein is highly homologous to SQSs from other plants. Using CsSQS-reporter assays, CsSQS was demonstrated to be endoplasmic reticulum membrane-bound. The coding region of CsSQS excluding transmemberane sequence was expressed in Escherichia coli. Recombinant CsSQS catalyzed the formation of squalene using farnesyl-pyrophosphate (FPP) as substrate with NADPH and Mg2+. In tea plant leaves, CsSQS expression was significantly induced by both herbivore and mechanical damages. Consistent with the stronger induction of CsSQS expression by mechanical damage than herbivory, tea plants injured mechanically released squalene as a volatile compound, which however was not detected from herbivore-damaged tea plants. Furthermore, it was found that the flowers of another tea plant cultivar Camellia sinensis var. assamica contain higher concentrations of squalene than the cultivar sinensis , indicating variations among tea plant varieties. With the identification and molecular characterization of squalene synthase in tea plant, next, we can ask the questions about the roles of squalene as a volatile product as well as a precursor for triterpenoids, which may promote product development from diverse tea materials and mining of excellent tea germplasm resources. • SQS gene in tea plant was isolated and the enzymatic activities of the encoded protein were identified. • Volatile squalene can be detected in flowers of C. sinensis var. assamica. • SQS release can be dramatically induced by mechanical damage in tea plant. [ABSTRACT FROM AUTHOR]

Terpenes and their derivatives are vital components of tea aroma. Their constitution and quantity are highly important criteria for the sensory evaluation of teas. Biologically, terpenes are involved in chemical resistance of tea plant against biotic and/or abiotic stresses. The goal of this study is to identify volatile terpenes of tea plants implicated in defense against herbivores and to identify terpene synthase (TPS) genes for their biosynthesis. Upon herbivory by tea geometrid (Ectropis obliqua Prout), tea plants were found to emit two sesquiterpenes, (E , E)-α-farnesene and (E)-nerolidol, which were undetectable in intact tea plants. The induced emission of (E , E)-α-farnesene and (E)-nerolidol suggests that they function in either direct or indirect defense of tea plants against the tea geometrid. Candidate TPS genes were identified from the transcriptomes of tea plants infested by tea geometrids. Two dedicated sesquiterpene synthases, Cs AFR and Cs NES2, were identified. Cs AFR belongs to the TPS-b clade and can catalyze the formation of (E , E)-α-farnesene from (E , E)-FPP. Cs NES2 belongs to the TPS-g clade and can synthesize (E)-nerolidol using (E , E)-FPP. The two genes were also both dramatically upregulated by herbivore damage. In summary, we showed that two novel sesquiterpene synthase genes CsAFR and CsNSE2 are inducible by herbivory and responsible for the elevated emission of herbivore-induced (E , E)-α-farnesene and (E)-nerolidol, which are implicated in tea plant defense against herbivores. • Identified two sesquiterpene synthase genes that are dedicated for the biosynthesis of (E , E)-α-farnesene and (E)-nerolidol, respectively. • The two genes can be induced by herbivore damages and emitted the products (E , E)-α-farnesene and (E)-nerolidol. • CsAFR and CsNSE2 are implicated in volatile-mediated defense of tea plants against herbivores. [ABSTRACT FROM AUTHOR]