Genes In Tea Plants Research Articles

Cytosolic Nudix Hydrolase 1 Is Involved in Geranyl β-Primeveroside Production in Tea.

Geraniol is a potent tea odorant and exists mainly as geranyl glycoside in Camellia sinensis. Understanding the mechanisms of geraniol biosynthesis at molecular levels in tea plants is of great importance for practical improvement of tea aroma. In this study, geraniol and its glycosides from tea plants were examined using liquid chromatography coupled with mass spectrometry. Two candidate geraniol synthase (GES) genes (CsTPS) and two Nudix hydrolase genes (CsNUDX1-cyto and CsNUDX1-chlo) from the tea genome were functionally investigated through gene transcription manipulation and gene chemical product analyses. Our data showed that in tea leaves, levels of geranyl β-primeveroside were dramatically higher than those of geranyl β-glucoside, while free geraniol was undetectable in this study. A tempo-spatial variation of geranyl β-primeveroside abundance in tea plants existed, with high levels in young and green tissues and low levels in mature or non-green tissues. Cytosolic CsNUDX1-cyto showed higher hydrolysis activity of geranyl-pyrophosphate to geranyl-monophosphate (GP) in vitro than did chloroplastidial CsNUDX1-chlo. A transgenic study revealed that expression of CsNUDX1-cyto resulted in significantly more geranyl β-primeveroside in transgenic Nicotiana benthamiana compared with non-transgenic wild-type, whereas expression of CsNUDX1-chlo had no effect. An antisense oligo-deoxynucleotide study confirmed that suppression of CsNUDX1-cyto transcription in tea shoots led to a significant decrease in geranyl β-primeveroside abundance. Additionally, CsNUDX1-cyto transcript levels and geranyl β-primeveroside abundances shared the same tempo-spatial patterns in different organs in the tea cultivar “Shucha Zao,” indicating that CsNUDX1-cyto is important for geranyl β-primeveroside formation in tea plants. Results also suggested that neither of the two candidate GES genes in tea plants did not function as GES in transgenic N. benthamiana. All our data indicated that CsNUDX1-cyto is involved in geranyl β-primeveroside production in tea plants. Our speculation about possible conversion from the chemical product of CsNUDX1-cyto to geranyl β-primeveroside in plants was also discussed.

Genome-Wide Characterization of the Cellulose Synthase Gene Superfamily in Tea Plants (Camellia sinensis)

The cellulose synthase gene superfamily, including Cellulose synthase A (CesA) and cellulose synthase-like (Csl) gene families, is responsible for the synthesis of cellulose and hemicellulose, respectively. The CesA/Csl genes are vital for abiotic stress resistance and shoot tenderness regulation of tea plants (Camellia sinensis). However, the CesA/Csl gene family has not been extensively studied in tea plants. Here, we identified 53 CsCesA/Csl genes in tea plants. These genes were grouped into five subfamilies (CsCesA, CsCslB, CsCslD, CsCslE, CsCslG) based on the phylogenetic relationships with Arabidopsis and rice. The analysis of chromosome distribution, gene structure, protein domain and motif revealed that most genes in CsCesA, CsCslD and CsCslE subfamilies were conserved, whereas CsCslB and CsCslG subfamily members are highly diverged. The transcriptome analysis showed that most CsCesA/Csl genes displayed tissue-specific expression pattern. In addition, members of CsCslB4, CsCesA1/3/6, CsCslB3/4, CsCslD3, CsCslE1 and CsCslG2/3 subfamilies were up-regulated under drought and cold stresses, indicating their potential roles in regulating stress tolerance in tea plants. Furthermore, the expression levels of CsCslG2_6 and CsCslD3_5 in different tissues and cultivars, respectively, were positively correlated with the cellulose content that is negatively related with shoot tenderness. Thus, these two genes were speculated to be involved in the regulation of shoot tenderness in tea plants. Our findings may help elucidate the evolutionary relationships and expression patterns of the CsCesA/Csl genes in tea plants, and provide more candidate genes responsible for stress tolerance and tenderness regulation in tea plants for future functional research.

Genome-wide identification, characterization, and expression analysis of the ammonium transporter gene family in tea plants (Camellia sinensis L.).

As a preferred nitrogen form, ammonium (NH4 + ) transport via specific transporters is particularly important for the growth and development of tea plants (Camellia sinensis L.). However, our understanding of the functions of the AMT family in tea plants is limited. We identified and named 16 putative AMT genes according to phylogenetic analysis. All CsAMT genes were divided into three groups, distributed on 12 chromosomes with only one segmental duplication repetition. The CsAMT genes showed different expression levels in different organs, and most of them were expressed mainly in the apical buds and roots. Complementation analysis of yeast mutants showed that CsAMTs restored the uptake of NH4 + . This study provides insights into the genome-wide distribution and spatial expression of AMT genes in tea plants.

Characterization of <i>CsWRKY29</i> and <i>CsWRKY37</i> transcription factors and their functional roles in cold tolerance of tea plant

The WRKY gene family is most widely known as being the key plant transcription factor family involved in various stress responses and affecting plant growth and development. In this study, a total of 86 members of the <italic>CsWRKY</italic> genes were identified from the tea plant genome. Most of these genes contain several important <italic>Cis</italic>-regulatory elements in the promoter regions associated with multiple stress-responses. These genes were further classified into three groups, I, II, and III, each with 21, 58, and 7 members, respectively. We showed evidence that tandem duplications, but not the whole genome duplication, are likely to drive the amplification of <italic>CsWRKY</italic> genes in tea plants. All the 86 <italic>CsWRKY</italic> genes showed differential expression patterns either in different tissues, or under exposure to diverse abiotic stresses such as drought, cold acclimation, and MeJA treatments. Additionally, the functional roles of two genes, <italic>CsWRKY29</italic> and <italic>CsWRKY37</italic>, were examined under cold stress; and the silencing of these genes resulted in tea plant phenotypes susceptible to cold stress. Moreover, transgenic <italic>Arabidopsis</italic> lines overexpressing <italic>CsWRKY29</italic> and <italic>CsWRKY37</italic> genes showed higher survival rates and lower malondialdehyde levels under freezing treatment than the wild type plants. The core findings from this work provide valuable evolutionary pattern of WRKY gene family and underpinning the underlying regulatory roles of <italic>CsWRKY29</italic> and <italic>CsWRKY37</italic> from tea plants that conferred cold tolerance in transgenic <italic>Arabidopsis</italic> plants.

Identification of PAL genes related to anthocyanin synthesis in tea plants and its correlation with anthocyanin content

The phenylalanine ammonia-lyase (PAL) gene family in tea plants (Camellia sinensis L.) encodes the enzyme that catalyzes the first reaction of the phenylpropane metabolic pathway. The present study aimed to characterize the PAL genes in tea plants, and get better insights on the CsPALs in anthocyanins accumulation. Seven CsPAL genes were identified and characterized in tea plants by bioinformatics analysis. Systematic analysis of CsPALs was conducted for its phylogenetic relationship, gene structure, chromosomal location, and protein conserved motifs based on tea plant genome. The cis-elements of CsPALs were responsive to light, abiotic stress, hormone, and MYB-binding site. Furthermore, tissue-specific expression analysis showed that CsPAL4 was expressed preferentially in young leaves and buds. Correlation analysis was performed in purple-leaf tea with anthocyanin components, and it was suggested that CsPAL4 was closely related with different anthocyanin accumulated, especially with cyanidin 3-O-galactoside, cyanidin 3-O-glucoside, and delphinidin 3-O-glucoside. Additionally, the putative upstream regulation factors CsMYBs (CsMYB59, CsARR1, CsSRM1, CsMYB101, and CsMYB52) and CsbHLHs (CsbHLH104, CsbHLH3, CsbIM1, CsTCP14, and CsPIF4) could bind to the promoter of CsPALs, thereby activating its transcription. This study provides a theoretical basis for further research to elucidate the functions of the CsPAL genes.

Divergent Response Strategies of CsABF Facing Abiotic Stress in Tea Plant: Perspectives From Drought-Tolerance Studies.

In plants, the bZIP family plays vital roles in various biological processes, including seed maturation, flower development, light signal transduction, pathogen defense, and various stress responses. Tea, as a popular beverage, is widely cultivated and has withstood a degree of environmental adversity. Currently, knowledge of the bZIP gene family in tea plants remains very limited. In this study, a total of 76 CsbZIP genes in tea plant were identified for the whole genome. Phylogenetic analysis with Arabidopsis counterparts revealed that CsbZIP proteins clustered into 13 subgroups, among which 13 ABFs related to the ABA signaling transduction pathway were further identified by conserved motif alignment and named CsABF1-13, these belonged to the A and S subgroups of CsbZIP and had close evolutionary relationships, possessing uniform or similar motif compositions. Transcriptome analysis revealed the expression profiles of CsABF genes in different tissues (bud, young leaf, mature leaf, old leaf, stem, root, flower, and fruit) and under diverse environmental stresses (drought, salt, chilling, and MeJA). Several CsABF genes with relatively low tissue expression, including CsABF1, CsABF5, CsABF9, and CsABF10, showed strong expression induction in stress response. Thirteen CsABF genes, were examined by qRT-PCR in two tea plant cultivars, drought-tolerant “Taicha 12” and drought-sensitive “Fuyun 6”, under exogenous ABA and drought stress. Furthermore, CsABF2, CsABF8, and CsABF11, were screened out as key transcription factors regulating drought tolerance of tea cultivars. Subsequently, some potential target genes regulated by CsABFs were screened by co-expression network and enrichment analysis. This study update CsbZIP gene family and provides a global survey of the ABF gene family in tea plant. The resolution of the molecular mechanism of drought resistance in different varieties could be helpful for improving stress resistance in tea plant via genetic engineering.

Identification and expression analysis of PUB genes in tea plant exposed to anthracnose pathogen and drought stresses

ABSTRACT The plant U-box (PUB) gene family, one of the major ubiquitin ligase families in plants, plays important roles in multiple cellular processes including environmental stress responses and resistance. The function of U-box genes has been well characterized in Arabidopsis and other plants. However, little is known about the tea plant (Camellia sinensis) PUB genes. Here, 89 U-box proteins were identified from the chromosome-scale referenced genome of tea plant. According to the domain organization and phylogenetic analysis, the tea plant PUB family were classified into ten classes, named Class I to X, respectively. Using previously released stress-related RNA-seq data in tea plant, we identified 34 stress-inducible CsPUB genes. Specifically, eight CsPUB genes were expressed differentially under both anthracnose pathogen and drought stresses. Moreover, six of the eight CsPUBs were upregulated in response to these two stresses. Expression profiling performed by qRT-PCR was consistent with the RNA-seq analysis, and stress-related cis-acting elements were identified in the promoter regions of the six upregulated CsPUB genes. These results strongly implied the putative functions of U-box ligase genes in response to biotic and abiotic stresses in tea plant.

New Insights into Stress-Induced β-Ocimene Biosynthesis in Tea (Camellia sinensis) Leaves during Oolong Tea Processing.

As the major contributors to the floral odors of tea products, terpenoid volatiles play critical roles in the defense response of plants to multiple stresses. Until now, only a few TPS genes in tea plants (Camellia sinensis) have been functionally validated. In this study, by comparative studies conducted at gene, protein, and metabolite levels during oolong tea processing, we isolated an ocimene synthase gene, CsOCS, which displays a low similarity to previously characterized tea ocimene synthases. Further prokaryotic expression and subcellular localization analysis showed that it is plastid-located and could produce (E)-β-ocimene and (Z)-β-ocimene using GPP as the substrate. The optimum temperature and pH of the enzyme were 30 °C and 7.5, respectively. Treatment with exogenous methyl jasmonate elevated the transcript level of CsOCS and enhanced the emission of ocimene from tea leaves. Collectively, CsOCS is implicated as a key enzyme for β-ocimene synthesis during oolong tea processing.

Gibberellin Increases the Bud Yield and Theanine Accumulation in Camellia sinensis (L.) Kuntze.

Tea (Camellia sinensis) is one of the most important cash crops in the world. Theanine, as an important amino acid component in tea, is a key quality index for excellent tea quality and high economic value. People increase theanine accumulation in tea mainly through the application of nitrogen fertilizer, shading and pruning. However, these methods are not effective. In this study, we treated tea buds with a 100 μM solution of GA3 containing 1‰ tween-20, investigated the effects of GA3 on theanine accumulation, bud yield, chlorophyll fluorescence parameters and expression level of theanine biosynthesis pathway genes in tea plant by qPCR, LC-MS/MS etc. Results showed that change trends of theanine and GA3 was extremely positively correlated with each other. Exogenous GA3 upregulated the expression level of theanine biosynthesis pathway genes, caused an increase of theanine content (mg·g-1) by 27% in tea leaves compared with Mock, and accelerated the germination of buds and elongation of shoots, which lead to a significant increase of tea yield by 56% (w/w). Moreover, the decrease of chlorophyll contents, photochemical quenching coefficient (qP) and relative electron transport rate (rETR) under GA3 treatment suggested that GA3 reduced photosynthesis in the tender tea leaves, indicating that the decline of carbon assimilation in tea plants was conducive to the nitrogen metabolism, and it was beneficial to the accumulation of theanine. This study provided a new technical and theoretical support for the precise control of tea quality components and phenophase.

Genome-wide identification of SULTR genes in tea plant and analysis of their expression in response to sulfur and selenium.

Sulfur (S) is an essential macronutrient required by plants. Plants absorb and transport S through sulfate transporters (SULTRs). In this study, we cloned 8 SULTR genes (CsSULTR1;1/1;2/2;1/3;1/3;2/3;3/3;5/4;1) from tea plant (Camellia sinensis), all of which contain a typical sulfate transporter and antisigma factor antagonist (STAS) conserved domain. Phylogenetic tree analysis further divided the CsSULTRs into four main groups. Many cis-acting elements related to hormones and environmental stresses were found within the promoter sequence of CsSULTRs. Subcellular localization results showed that CsSULTR4;1 localized in the vacuolar membrane and that other CsSULTRs localized to the cellular membrane. The tissue-specific expression of the 8 CsSULTR genes showed different expression patterns during the active growing period and dormancy period. In particular, the expression of CsSULTR1;1 was highest in the roots, but that of CsSULTR1;2 was lowest in the dormancy period. The expression of CsSULTR1;1/1;2/2;1/3;2 was stimulated under different concentrations of selenium (Se) and S; moreover, CsSULTR1;2/2;1/3;3/3;5 was upregulated in response to different valences of Se.

Divergent DNA methylation contributes to duplicated gene evolution and chilling response in tea plants.

The tea plant (Camellia sinensis) is a thermophilic cash crop and contains a highly duplicated and repeat-rich genome. It is still unclear how DNA methylation regulates the evolution of duplicated genes and chilling stress in tea plants. We therefore generated a single-base-resolution DNA methylation map of tea plants under chilling stress. We found that, compared with other plants, the tea plant genome is highly methylated in all three sequence contexts, including CG, CHG and CHH (where H=A, T, or C), which is further proven to be correlated with its repeat content and genome size. We show that DNA methylation in the gene body negatively regulates the gene expression of tea plants, whereas non-CG methylation in the flanking region enables a positive regulation of gene expression. We demonstrate that transposable element-mediated methylation dynamics significantly drives the expression divergence of duplicated genes in tea plants. The DNA methylation and expression divergence of duplicated genes in the tea plant increases with evolutionary age and selective pressure. Moreover, we detect thousands of differentially methylated genes, some of which are functionally associated with chilling stress. We also experimentally reveal that DNA methyltransferase genes of tea plants are significantly downregulated, whereas demethylase genes are upregulated at the initial stage of chilling stress, which is in line with the significant loss of DNA methylation of three well-known cold-responsive genes at their promoter and gene body regions. Overall, our findings underscore the importance of DNA methylation regulation and offer new insights into duplicated gene evolution and chilling tolerance in tea plants.

Low temperature effects on carotenoids biosynthesis in the leaves of green and albino tea plant (Camellia sinensis (L.) O. Kuntze)

Tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most important economic crops worldwide, and it has a positive effect on human health. The low temperature in late autumn and early/late spring cold often cause damage to the normal physiological activities of tea plant, thereby reducing the quality and yield of tea. As one of the essential pigment of higher plant, carotenoids play an important role in the physiological activities of higher plant. In addition, as an important precursor of tea aroma volatiles, carotenoids are the important factors involved in the formation of tea quality. In this study, the main carotenoids, lutein and β-carotene, in leaves of common green tea cultivar 'Longjing 43′ and albino tea cultivar 'White leaf No.1′ were detected after low temperature treatment at 4 ℃. The results showed that the contents of lutein and β-carotene in 'Longjing 43′ were higher than that in 'White leaf No.1′, respectively. The chlorophyll content in two tea cultivars decreased and was significant positive correlation with two kinds of carotenoid content at low temperature. Under low temperature, the genes related to the biosynthesis pathway of methylerythritol 4-phosphate (MEP) and carotenoids all showed varying degrees of response with the changes of lutein and β-carotene content. The relative expression levels of CsDXS1, CsPSY1 and CsCHXB were up-regulated and higher than other related genes. Expression analysis of carotenoids biosynthesis genes and its correlation with carotenoids accumulation confirmed the regulatory role of structural genes in tea plant at low temperature. Promoter prediction results showed that the CsDXR, CsHDS1 and CsCHXB contain low-temperature response element LTR. This study provides reference for further study on the dynamic changes of carotenoids during the growth of tea plant.

R2R3-MYB transcription factor family in tea plant (Camellia sinensis): Genome-wide characterization, phylogeny, chromosome location, structure and expression patterns

MYB transcription factors play essential roles in many biological processes and environmental stimuli. However, the functions of the MYB transcription factor family in tea plants have not been elucidated. Here, a total of 122 CsR2R3-MYB genes were identified from the chromosome level genome of tea plant (Camellia sinensis). The CsR2R3-MYB genes were phylogenetically classified into 25 groups. Results from the structure analysis of the gene, conserved motifs, and chromosomal distribution supported the relative conservation of the R2R3-MYB genes family in the tea plant. Synteny analysis indicated that 122, 34, and 112 CsR2R3-MYB genes were orthologous to Arabidopsis thaliana, Oryza sativa and C. sinensis var. ‘huangdan’ (HD), respectively. Tissue-specific expression showed that all CsR2R3-MYB genes had different expression patterns in the tea plant tissues, indicating that these genes may perform diverse functions. The expression patterns of representative R2R3-MYB genes and the regulatory network of the main anthocyanin components were analyzed, which suggested that CsMYB17 may played a key role in the regulation of cya-3-O-gal, del-3-O-gal, cya-3-O-glu and pel-3-O-glu. Results from the qRT-PCR validation of selected genes suggested that CsR2R3-MYB genes were induced in response to drought, cold, GA, and ABA treatments. Overall, this study provides comprehensive and systematic information for research on the function of R2R3-MYB genes in tea plants.

Genome-Wide Identification and Characterization of the CsFHY3/FAR1 Gene Family and Expression Analysis under Biotic and Abiotic Stresses in Tea Plants (Camellia sinensis).

The FHY3/FAR1 transcription factor family, derived from transposases, plays important roles in light signal transduction, and in the growth and development of plants. However, the homologous genes in tea plants have not been studied. In this study, 25 CsFHY3/FAR1 genes were identified in the tea plant genome through a genome-wide study, and were classified into five subgroups based on their phylogenic relationships. Their potential regulatory roles in light signal transduction and photomorphogenesis, plant growth and development, and hormone responses were verified by the existence of the corresponding cis-acting elements. The transcriptome data showed that these genes could respond to salt stress and shading treatment. An expression analysis revealed that, in different tissues, especially in leaves, CsFHY3/FAR1s were strongly expressed, and most of these genes were positively expressed under salt stress (NaCl), and negatively expressed under low temperature (4 °C) stress. In addition, a potential interaction network demonstrated that PHYA, PHYC, PHYE, LHY, FHL, HY5, and other FRSs were directly or indirectly associated with CsFHY3/FAR1 members. These results will provide the foundation for functional studies of the CsFHY3/FAR1 family, and will contribute to the breeding of tea varieties with high light efficiency and strong stress resistance.

Genome-wide identification, characterization, and expression analysis of tea plant autophagy-related genes (CsARGs) demonstrates that they play diverse roles during development and under abiotic stress

BackgroundAutophagy, meaning ‘self-eating’, is required for the degradation and recycling of cytoplasmic constituents under stressful and non-stressful conditions, which helps to maintain cellular homeostasis and delay aging and longevity in eukaryotes. To date, the functions of autophagy have been heavily studied in yeast, mammals and model plants, but few studies have focused on economically important crops, especially tea plants (Camellia sinensis). The roles played by autophagy in coping with various environmental stimuli have not been fully elucidated to date. Therefore, investigating the functions of autophagy-related genes in tea plants may help to elucidate the mechanism governing autophagy in response to stresses in woody plants.ResultsIn this study, we identified 35 C. sinensis autophagy-related genes (CsARGs). Each CsARG is highly conserved with its homologues from other plant species, except for CsATG14. Tissue-specific expression analysis demonstrated that the abundances of CsARGs varied across different tissues, but CsATG8c/i showed a degree of tissue specificity. Under hormone and abiotic stress conditions, most CsARGs were upregulated at different time points during the treatment. In addition, the expression levels of 10 CsARGs were higher in the cold-resistant cultivar ‘Longjing43’ than in the cold-susceptible cultivar ‘Damianbai’ during the CA period; however, the expression of CsATG101 showed the opposite tendency.ConclusionsWe performed a comprehensive bioinformatic and physiological analysis of CsARGs in tea plants, and these results may help to establish a foundation for further research investigating the molecular mechanisms governing autophagy in tea plant growth, development and response to stress. Meanwhile, some CsARGs could serve as putative molecular markers for the breeding of cold-resistant tea plants in future research.

Genome-wide identification, characterization and expression analysis of the expansin gene family under drought stress in tea (Camellia sinensis L.)

During several developmental processes, expansins contribute to cell enlargement by promoting cell wall loosening. To explore the biological roles of expansins during drought stress response and to characterize different expansins in tea, we performed a detailed analysis of the expansin gene family covering phylogeny, gene structure, profiling of gene expression and co-expression network analysis. We identified a total of 40 expansin genes in the tea genome belonging to 3 subfamilies, out of which 29 tea expansins belong to EXPA, 9 to EXLA and 2 to EXPB subfamilies. A minimum of 3 and a maximum of 13 exons are present in the gene structure of expansins. Presence of drought stress responsive cis-acting elements in the upstream of promoter regions of 40% of the identified expansins shows that the putative expansins may have been involved in tea plant’s response to drought stress. At least 15 out of the 40 expansin genes are found to be differentially expressed in response to drought in each of the drought stress related public datasets analysed in-silico. TEA022767 belonging to EXPA subfamily is seen to be upregulated during drought stress, as revealed from the analysis of all three publicly available bio-projects. Co-expression network analysis shows that TEA022767 and TEA032954 form a connecting link between two expression correlation groups that further signifies their role in drought stress response in tea. This study helps to interpret and to understand the biological roles of diverse expansin genes in tea plants under drought stress conditions.

Genome-Wide Identification of Seven Polyamine Oxidase Genes in Camellia sinensis (L.) and Their Expression Patterns Under Various Abiotic Stresses.

Polyamines (PAs) in plant play a critical role in growth and development and in response to environmental stress. Polyamine oxidase (PAO) is a flavin adenine dinucleotide dependent enzyme that plays a major role in PA catabolism. For the first time, PAO genes in tea plant were screened for the whole genome-wide and seven CsPAO genes were identified, which were named CsPAO1-7. Phylogenetic tree analysis revealed seven CsPAO protein sequences classed into three groups, including clade I, III, and IV. Compared with other plants, the tea plant lacked clade II members. Genetic structure and tissue specific expression analysis showed that there were significant differences among members of the CsPAO gene family. Among members of the CsPAOs family, CsPAO4 and CsPAO5 contain more introns and are highly expressed in various organizations. CsPAO1, CsPAO4, and CsPAO5 genes were cloned and expressed heterologously to verify theirs function. Heat map showed high response of CsPAO5 to drought stress, while CsPAO1 and CsPAO2 were sensitive to changes in nitrogen nutrition. Furthermore, exogenous abscisic acid (ABA) treatment indicated that the expression of most CsPAO genes in roots and leaves was significantly induced. In the root, Spm content increased significantly, while Put and Spd content decreased, suggesting that ABA has great influence on the biosynthesis of PAs. Anaerobic treatment of picked tea leaves showed that the decomposition of PAs was promoted to a certain extent. The above data help to clarify the role of CsPAO in response abiotic and nitrogen nutritional stresses in tea plants, and provide a reference perspective for the potential influence of PAs on the tea processing quality.

HAK/KUP/KT family potassium transporter genes are involved in potassium deficiency and stress responses in tea plants (Camellia sinensis L.): expression and functional analysis

BackgroundTea plant is one of the most important non-alcoholic beverage crops worldwide. While potassium (K+) is an essential macronutrient and greatly affects the growth and development of plants, the molecular mechanism underlying K+ uptake and transport in tea plant root, especially under limited-K+ conditions, is still poorly understood. In plants, HAK/KUP/KT family members play a crucial role in K+ acquisition and translocation, growth and development, and response to stresses. Nevertheless, the biological functions of these genes in tea plant are still in mystery, especially their roles in K+ uptake and stress responses.ResultsIn this study, a total of 21 non-redundant HAK/KUP/KT genes (designated as CsHAKs) were identified in tea plant. Phylogenetic and structural analysis classified the CsHAKs into four clusters (I, II, III, IV), containing 4, 8, 4 and 5 genes, respectively. Three major categories of cis-acting elements were found in the promoter regions of CsHAKs. Tissue-specific expression analysis indicated extremely low expression levels in various tissues of cluster I CsHAKs with the exception of a high root expression of CsHAK4 and CsHAK5, a constitutive expression of clusters II and III CsHAKs, and a moderate cluster IV CsHAKs expression. Remarkably, the transcript levels of CsHAKs in roots were significantly induced or suppressed after exposure to K+ deficiency, salt and drought stresses, and phytohormones treatments. Also notably, CsHAK7 was highly expressed in all tissues and was further induced under various stress conditions. Therefore, functional characterization of CsHAK7 was performed, and the results demostrated that CsHAK7 locates on plasma membrane and plays a key role in K+ transport in yeast. Taken together, the results provide promising candidate CsHAKs for further functional studies and contribute to the molecular breeding for new tea plants varieties with highly efficient utilization of K+.ConclusionThis study demonstrated the first genome-wide analysis of CsHAK family genes of tea plant and provides a foundation for understanding the classification and functions of the CsHAKs in tea plants.

Genome-wide identification and expression analysis of SABATH methyltransferases in tea plant (Camellia sinensis): insights into their roles in plant defense responses

ABSTRACT SABATH methyltransferases convent plant small-molecule metabolites into volatile methyl esters, which play important roles in many biological processes and defense reactions in plants. In this study, a total of 32 SABATH genes were identified in the Camellia sinensis var. sinensis (CSS) genome, which were renamed CsSABATH1 to CsSABATH32. Genome location annotation suggested that tandem duplication was responsible for the expansion of SABATH genes in tea plant. Multiple sequence alignment and phylogenetic analysis showed that the CsSABATHs could be classified into three groups (I, II and III), which were also supported by gene structures and conserved motifs analysis. Group II contained only two CsSABATH proteins, which were closely related to PtIAMT, AtIAMT and OsIAMT. The group III SABATH genes of tea plant exhibited expansion on the CSS genome compared with Camellia sinensis var. assamica (CSA) genome. Based on RNA-seq data, the CsSABATHs exhibited tissue-specific expression patterns, and the members with high expression in buds and young leaves were also obviously upregulated after MeJA treatment. The expression of many transcription factors was significantly correlated with that of different members of the CsSABATH gene family, suggesting a potential regulatory relationship between them. Quantitative real-time PCR (qPCR) expression analysis showed that CsSABATHs could respond to exogenous JA, SA and MeSA treatments in tea plants. RNA-seq data analysis and qPCR validation suggested that CsSABATH8, 11, 16, 25, 29 and 32 might play a special role in plant defense against insect herbivory. These results provide references for evolutionary studies of the plant SABATH family and the exploration of the potential roles of CsSABATHs in tea plant defense responses.

Isolation and expression profiles of class III PRX gene family under drought stress in Camellia sinensis

The class III PRX family is a class of heme-containing oxidases and plays important roles in response to abiotic stress in plants. The responses to abiotic stresses could be regulated by phytohormones like abscisic acid (ABA) and methyl jasmonate (MeJA). In this research, 11 CsPRXs genes in tea plant (Camellia sinensis) were cloned and analyzed. Based on the similarity of the sequences, they were classified into 5 sub-groups. According to the results of reverse transcription PCR, CsPRX55 presented the highest expression in roots compared to stems and leaves of both tea cultivars LJ43 and Baiye 1. Besides, the expressions of CsPRX12 and CsPRX73 were highest in roots, while CsPRX4, CsPRX47, and CsPRX72 were highest in stems of 'Baiye 1'. But most of CsPRXs showed the highest expressions in leaves of 'LJ43'. CsPRXs appeared different expression patterns under drought stress of tea plants which were pre-treated with ABA or MeJA for three days. In 'LJ43' and 'Baiye 1', there were 3 CsPRXs and 7 CsPRXs up-regulated by exogenous ABA and MeJA, respectively. However, CsPRX4 and CsPRX16 were down-regulated in 'LJ43' treated with ABA and MeJA. It suggested that CsPRXs possessed diverse functions in response to hormones and abiotic stress. In 'LJ43', the activity of peroxidase (POD) was increased when pre-treated by ABA and MeJA, and the highest activity appeared after 24 and 12 h, respectively. In 'Baiye 1', the activity of POD was also increased, however, when pre-treated by MeJA, the peak-time of POD activity was at 24 h. But the change had no obvious rule after ABA treatment. Exogenous ABA or MeJA may play a role in protecting tea plants suffered from drought stress via regulating some CsPRXs expressions and increasing POD activity.