Drought stress (DS) significantly impairs seedling growth, development, and quality worldwide, underscoring the need for effective mitigation strategies. Biochar (BC) and vermicompost (VC) are promising amendments that can improve plant growth and help plants cope with stress. However, their combined effects on tea (Camellia sinensis (L.) Kuntze) seedlings, particularly in relation to morphology, photosynthesis, and antioxidant responses under DS, remain poorly understood. In this study, we tested how BC and VC, both alone and together, affect tea seedlings under DS. Co-application of BC and VC improved growth, photosynthesis traits, and antioxidant activity. Specifically, this treatment increased chlorophyll a (117 %), chlorophyll b (219 %), carotenoids (200 %), PSII efficiency (104 %), photosynthesis rate (78 %), intracellular CO2 levels (75 %), and transpiration (98 %) compared with drought alone. Important photosynthesis-related genes such as CsPsaG, CsPsbS, CsLHCA, CsLHCB, and CsCLH were also upregulated. Tea quality also improved. Levels of caffeine (10.4 %), polyphenols (33.9 %), theanine (140.5 %), amino acids (9.4 %) and catechin (21.95 %) all increased under the combined BC and VC treatment. Antioxidant enzymes such as catalase (40.8 %), superoxidase dismutase (69.6 %), peroxidase (85.3 %) and reduced glutathione (103.8 %) also became more active. Key antioxidant genes CsPOD, CsCAT, CsSOD, and CsAPX were expressed at higher levels. Scanning and transmission electron microscopy showed that combined BC and VC helped protect plant structures. They reduced drought-induced damage to stomata, guard cells, and mesophyll cells. Confocal microscopy imaging showed that cellular integrity was better preserved. Overall, the co-application of BC and VC is a promising and effective strategy to improve growth, physiology, and drought tolerance in tea seedlings.

Trichomes in plants serve not only to secrete secondary metabolites and defend against biotic and abiotic stresses, but also influence the quality of processed products in species such as tea plants (Camellia sinensis). However, the distribution patterns of plant trichomes and the environmental adaptability of tea plant trichomes remain poorly characterized. This study reveals a distinct polar distribution of trichomes along the adaxial-abaxial, proximal-distal, and medial-lateral axes of tea plant leaves. Trichome density on both leaves and stems decreases with developmental maturation, while trichomes on leaves exhibit greater length but lower density compared to those on stems. The broad-sense heritability of trichome diameter, length, and density is remarkably high, although their coefficients of variation differ significantly. Tea plant cultivars can be classified into three categories: low trichome abundance, moderate abundance, and high abundance. Long-term drought significantly increased trichome length and density, whereas long-term shading exposure produced the opposite effect. Key trichome development genes exhibited differential responsiveness to tissue type, drought, and shade treatments in tea plants. These findings provide insights into the distributional principles of plant trichomes and facilitate the scientific utilization and genetic improvement of trichomes in tea plants.

In northern China's tea plantations - where extreme drought is uncommon - subtle yet persistent mild drought increasingly shapes tea yield and quality. However, how tea plants link mild drought-induced secondary metabolite accumulation to drought tolerance remains unknown. By integrating RNA-seq analysis with functional validation and regulatory network characterization of CsTCP14b, we demonstrate that this transcription factor promotes flavonol biosynthesis, thereby enhancing reactive oxygen species (ROS) scavenging and conferring early-stage drought tolerance in tea plants. CsTCP14b is rapidly induced during early drought stress and directly activates CsFLSb transcription by binding to its promoter, leading to increased accumulation of the flavonols kaempferol and quercetin and enhanced ROS detoxification. Yeast library screening and targeted interaction assays further identified HD-ZIP III transcription factor CsREV as an interacting partner. The CsREV-CsTCP14b interaction promotes nuclear retention of CsTCP14b and strengthens its activation of CsFLSb. Cross-cultivar analyses confirmed that the CsTCP14b-CsREV-CsFLSb module is conserved. Under drought stress, the drought-tolerant cultivar Zhongcha 108 (ZC108) shows rapid induction of CsTCP14b and CsREV and increased flavonol accumulation, whereas these responses are weaker in the drought-sensitive cultivar Wuniuzao (WNZ). These findings provide mechanistic insight into tea plant adaptation to mild drought and offer molecular targets for breeding drought-resilient, high-quality tea cultivars.

Tea (Camellia sinensis L. O. Kuntze) is an important economic crop widely cultivated in tropical and sub-tropical regions, where drought stress often limits its growth and productivity. Soil application of nano-biochar (nBC) and nano-calcium oxide (nCaO) offers a promising approach for enhancing soil health, tea quality, and yield. A pot experiment was executed to explore the synergistic effects of nBC and nCaO on soil enzymatic and microbial activities, N-P-C cycling genes, and the quality and yield of tea seedlings under drought stress. The results showed that, under drought stress, the combined application of nBC and nCaO significantly improved the soil physico-chemical and microbial properties viz. an increase in soil pH (23.29%), soil organic matter (53.18%), soil total carbon (30.56%), available N (63.12%), available P (140.85%), available K (32.92%), microbial biomass carbon (9.90%) and microbial biomass N (8.23%) compared with the control. This may have been due to manifold increase in the expression levels of N-C-P cycling genes such as phoD (5.2-fold), phoC (7.0-fold), narG (3.4-fold) and GH31 (1.8-fold) and relatively higher abundance of archaeal and bacterial communities. Soil urease, acid-phosphatase, nitrate reductase, β-glucosidase, catalase, phosphomonoesterase, and N-acetyl-β-d-glucosaminidase enzyme values were 48.32, 13.34, 100.00, 43.37, 612.5, 61.30, and 43.65% higher, respectively, in soils amended with both nBC and nCaO than in the control under drought stress. Furthermore, co-application of nBC and nCaO significantly enhanced tea quality traits such as caffeine (5.89%), polyphenol (12.24%), total catechins (11.00%) and amino acid (16.17%), as well as yield parameters including plant height (10.43%), leaf area (97.55%) and 10-bud weight (42.53%) relative to the control. Overall, the combined application of nBC and nCaO substantially improved soil enzymatic and microbial activities, as well as tea quality and yield traits, under drought stress.

Excessive use of chemical fertilizers leads to environmental pollution and a decline in tea quality. To promote sustainable development while maintaining high-quality productivity, reducing nitrogen fertilizer application is an effective strategy for cost savings and emission reduction in tea plantations. However, there is a lack of integration and testing with other efficiency-enhancing measures. This study explores the potential of moderate shading to mitigate the negative effects of reduced nitrogen fertilizer on the growth and quality of clonal tea plant. Focusing on the local variety 'Shaancha 1', this study uses field experiments to evaluate the growth and quality components of tea plant under different combinations of nitrogen fertilizer concentrations (0, 90, 180, 360 kg N ha-1) and shading treatments, which include varying shading durations (0, 7, 38 d) and intensities (0%, 40%, 70%). Results showed that, compared to the traditional high-nitrogen fertilization regime, applying 180 kg N ha-1 combined with a short-term shading duration of 7 d and 40% shading intensity promoted tea plant growth by enhancing antioxidant capacity. This treatment also ensured tea yield and improved the content of several quality components. The combination of low-level shading and reduced nitrogen fertilizer application is an empirical case that enhances tea yield and quality. It provides practical measures for eco-friendly tea cultivation while also helping to lower costs and emissions.

Cold stress is a widely distributed abiotic stress that severely limits the yield and quality of tea plants. Tryptophan (Trp) and downstream indole compounds play an important role in plant growth and stress response. However, beyond its involvement in indole compounds synthesis, the other physiological functions of Trp in tea plants remain unknown. In this study, anthranilate synthetase (ASA2) was a positive regulator to enhance cold stress tolerance in Camellia sinensis. The expression of CsASA2 was strongly induced by cold stress. Suppression of CsASA2 expression in C. sinensis reduced the accumulation of Trp, lowered reactive oxygen species (ROS) scavenging capacity, and ultimately impaired cold stress tolerance. Heterologous overexpression of CsASA2 increased the endogenous Trp and melatonin content in response to cold stress and then showed the opposite cold resistance trend. Further study revealed that CsASA2 expression was positively regulated by the transcription factor CsERF21-l. Low temperature induced and kept CsERF21-l expression at a relatively high level. Suppression of CsERF21-l expression in tea plant reduced the accumulation of IAA and melatonin, increased the extent of cytoplasmic membrane damage, and weakened the cold tolerance of tea plant. Further, our study demonstrated that CsERF21-l enhanced cold tolerance in tea plants by promoting CsASA2 transcription. Overall, our results showed that the CsERF21-l-CsASA2 model balances the growth and cold tolerance in tea plants by regulating melatonin and IAA levels by recruiting Trp under cold stress.

Tea gray blight is a prevalent fungal leaf disease affecting tea plants. It primarily targets tea leaves, and in severe cases, significantly impairs tea yield and quality. In this study, leaf samples displaying tea gray blight symptoms were collected from the tea plantation base in Xixiang County, Shaanxi Province, China. Pathogenic fungi were isolated using the tissue isolation method and identified through a combination of morphological, pathogenicity, and molecular biological analyses. The main pathogenic fungi were identified as belonging to the genera Pestalotiopsis, Neopestalotiopsis, and Pseudopestalotiopsis. Concurrently, eight bacterial strains with remarkable antagonistic effects against the pathogenic fungi were isolated from the rhizosphere soil of severely infected tea plants. Through 16S rDNA sequence analysis, these antagonistic bacteria were identified as Streptomyces castaneus, Bacillus velezensis, three strains of B. subtilis, Microbacterium sp., B. amyloliquefaciens, and Streptomyces sp., respectively. All eight antagonistic bacteria demonstrated the capacity to produce indole-3-acetic acid (IAA), among them, strain X8 exhibited the highest IAA production, reaching 107.2 mu g/mL. Further research found that four strains of antagonistic bacteria named X10, X11, X14, and X17-B showed particularly significant inhibitory effects on the five strains of pathogenic bacteria. Additionally, the antagonistic bacteria in the soil exhibit a certain level of resistance to adverse conditions. Among them, both X10 and X17-B showed high salt tolerance, while X21 showed better drought tolerance. This study provides a selection basis for the development of biocontrol agents suitable for the winter closing garden management of tea plants and microbial agents of bio-organic fertilizers used for applying base fertilizers in autumn.

The global issue of insecticide resistance among pests is a major concern. Ectropis grisescens Warren (Lepidoptera: Geometridae), is a highly destructive leaf-eating pest distributed in tea plantations throughout China and Japan, and has exhibited resistance to various insecticides. Recent studies suggest that insect symbionts play a role in influencing insecticide resistance, however, their specific involvement in E. grisescens remains unclear. Here, we initially selected appropriate antibiotic mixtures at a concentration of 300 mu g ml- 1. The bioassay results showed that the insecticide susceptibility of the E. grisescens population treated with antibiotic mixtures significantly increased exposed to bifenthrin. Comparative analysis revealed that the LC50 value, survival rate, P450 enzyme activity, and relative content of Wolbachia in the E. grisescens population treated with 300 mu g ml- 1 tetracycline were notably lower than those treated with other antibiotics (ampicillin, gentamicin, and streptomycin). Moreover, the population treated with 2.5 mg ml- 1 tetracycline exhibited even greater reductions in these parameters than the 300 mu g ml- 1 tetracycline-treated group. Additionally, 16S rRNA sequencing results showed a significant decrease in xenobiotics metabolism by cytochrome P450 in the E. grisescens population treated with 2.5 mg ml- 1 tetracycline. Transcriptome analysis showed a significant down-regulation of two cytochrome P450 genes in E. grisescens population without Wolbachia. These results suggest that Wolbachia may contribute to the resistance of E. grisescens to bifenthrin by regulating cytochrome P450 genes, providing a foundation for further study on the mechanism of symbiont-mediated host detoxification metabolism in insect pests.

The HD-Zip IV transcription factors, which belong to the homeodomain leucine zipper (HD-ZIP) family, are essential for the development of epidermal cells in plants. However, there is limited information about HD-Zip IV in tea plant (Camellia sinensis L.). Here we identified 10 HD-Zip IV members (CsHDZIV1 10) in tea plant, which are distributed in 8 chromosomes with two segmentally duplicated gene pairs. The exon number of CsHDZIVs ranges from 9 to 11, with most genes having two conserved motifs in the 3'UTR. CsHDZIV1 9 have almost identical motifs and tertiary structures. The promoter region of CsHDZIVs was predicted to harbor light, phytohormone, stress, growth and developmental elements. 9 CsHDZIVs are divided into 5 subfamilies and located in the nucleus. They exhibited expression trends across 12 tea plant tissues and responded to PEG, cold, NaCl and shading treatments. CsHDZIV3 overexpression partially and completely restored trichome development defects of gl2 leaves and stems, respectively. CsHDZIV3 showed histochemical staining in Arabidopsis trichomes and protein interaction with itself. It might regulate trichome development through forming homodimers. These findings contribute to functional study of tea plant HD-Zip IV and provide guiding significance for the investigation of trichome development and the improvement of trichome traits.

Nitrogen (N) fertilizer management is pivotal for guaranteeing higher yield and better quality of crops. In recent years, significant efforts have been devoted to enhancing N-use efficiency in field crops. However, comprehensive fertilization management of the tea plantation, which is necessary to meet the standards of an organic tea garden, has been overlooked. Herein, a field experiment was conducted to explore appropriate fertilization patterns for alpine tea plantations in southern Shaanxi (China). The effects of annual N fertilization rates viz. control, inorganic N at 300, 600, and 900 kg N hm-2 along with sole and combined bioorganic fertilizer application at 450 kg N hm-2 on soil characteristics, yield, quality, and resistance of fresh tea leaves were studied in summer. Results showed that proper N application significantly increased fresh leaves' yield and improved the overall quality. Compared to the control, N application at 300 kg N hm-2 along with bioorganic fertilizer showed a significant improvement in soil characteristics such as nutrient availability. Moreover, a reduction in soil bulk density and an increase in organic matter content were also recorded for the same treatment. In addition, the above-mentioned N treatment enhanced fresh leaves' yield and quality parameters compared to other treatments. Also, low inorganic N combined with bioorganic fertilizer improved the overall N use efficiency and plant resistance to harsh summer conditions. Therefore, N application at 300 kg N hm-2 along with bioorganic fertilizer presents a sustainable solution for improving soil conditions and the performance of tea seedlings even under harsh summer conditions.

Cultivating drought-tolerant tea varieties enhances both yield and quality of tea plants in northern China. However, the mechanisms underlying their drought tolerance remain largely unknown. Here we identified a key regulator called CsREV, which differentially regulates xylem patterns between leaves and stems, thereby conferring drought tolerance in tea plants. When drought occurs, upregulation of CsREV activates the CsVND7a-dependent xylem vessel differentiation. However, when drought persists, the vessel differentiation is hindered as CsVND7a is downregulated by CsTCP4a. This, combined with the CsREV-promoted secondary-cell-wall thickness of xylem vessel, leads to the enhanced curling of leaves, a characteristic closely associated with plant drought tolerance. Notably, this inhibitory effect of CsTCP4a on CsVND7a expression is absent in stems, allowing stem xylem vessels to continuously differentiate. Overall, the CsREV-CsTCP4-CsVND7 module is differentially utilized to shape the xylem patterns in leaves and stems, potentially balancing water transportation and utilization to improve tea plant drought tolerance.

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule, which has been shown to play an important role in plant growth and development by coupling with various phytohormones. However, the relationship between H2S and cytokinin (CTK) and the mechanisms by which H2S and CTK affect root growth remain poorly understood. Endogenous CTK was analyzed by UHPLC-ESI-MS/MS. Persulfidation of cytokinin oxidase/dehydrogenases (CKXs) was analyzed by mass spectrometry (MS). ckx2/CKX2wild-type (WT), OE CKX2 and ckx2/CKX2Cys(C)62alanine(A) transgenic lines were isolated with the ckx2 background. H2S is linked to CTK content by CKX2, which regulates root system architecture (RSA). Persulfidation at cysteine (Cys)62 residue of CKX2 enhances CKX2 activity, resulting in reduced CTK content. We utilized 35S-LCD/oasa1 transgenic lines to investigate the effect of endogenous H2S on RSA, indicating that H2S reduces the gravitropic set-point angle (GSA), shortens root hairs, and increases the number of lateral roots (LRs). The persulfidation of CKX2Cys62 changes the elongation of cells on the upper and lower flanks of LR elongation zone, confirming that Cys62 of CKX2 is the specificity target of H2S to regulate RSA in vivo. In conclusion, this study demonstrated that H2S negatively regulates CTK content and affects RSA by persulfidation of CKX2Cys62 in Arabidopsis thaliana.

The tea green leafhopper (TGLH), Empoasca (Matsumurasca) onukii Matsuda, poses a significant challenge to tea cultivation in East Asia because of its ability to infest specific tea plant cultivars. Here, we investigated the complex interactions between TGLHs, various tea cultivars, and their symbiotic microbiota, especially the effect of arginine on host selection. A detailed two-year field study involving 16 tea cultivars, coupled with controlled laboratory and field experiments, was conducted to establish a clear link between TGLH infestation and the arginine content of tea plants. Metagenomic analysis revealed a predominance of bacterial taxa in TGLHs, primarily from the phylum Proteobacteria, with significant contributions from orders such as Pseudomonadales, Enterobacterales, and Flavobacteriales, which are crucial for the biosynthesis of essential amino acids but lack the argF gene necessary for arginine synthesis. The absence of the argF gene indicates the potential presence of microbial-mediated dietary adaptation strategies in TGLHs. Additionally, our research examines microbial diversity within TGLH populations and confirms the critical role that symbiotic bacteria play in influencing dietary preferences. The results of our study provide insights into the dynamic interplay between pests, plants, and microorganisms. Our findings are preliminary, and further research is needed to explore the potential applications of symbiotic bacteria in sustainable tea cultivation and integrated pest management strategies.

The availability of soil phosphorus (P) is essential for crop cultivation and production. However, agronomic P management for tea crops remains unexplored. Herein, the effect of different P management practices viz. unfertilized (control), organic fertilizer (OF) application, OF + N application at 300 kg/ha (N300) (OF-P1), OF + N300 + P application at 45 kg/ha (OF-P2), OF + N300 + P application at 90 kg/ha (OF-P3), and OF + N300 + P application at 135 kg/ha (OF-P4) on soil nutrient acquisition, enzymatic activities, and physio-biochemical, and quality traits of tea plants are investigated in yield. The results showed that OF-P2 treatment had significantly higher soil N (30.5%), P (42.2%), and potash (1.6%) concentrations above the control. P concentrations had a linear positive correlation with the activities of acid-phosphatase and phytase. OF-P2 had the greatest effects on plant growth, chlorophyll and carotenoid contents, and antioxidative enzyme activities than other treatments. OF-P2 treatment had a two-fold decrease in hydrogen peroxide and dioxygen (singlet) compared to the control. It was further found that OF-P2 significantly increased amino acid content by 33.5%, 40.1%, and 31.9%, and decreased polyphenol content by 42.3%, 45.6%, and 25.7% in bud, first, and second leaf, respectively, above the control. Overall, the present findings suggest that low P application (OF-P2) can increase nutrient availability, bud quality, and yield by improving soil enzymatic activities, pigment contents, and antioxidative activities. Establishing this mode of low P application may provide an optimum strategy for enhancing crop performance in regions where unreasonable P application practices are common.

Strigolactones (SLs) play crucial roles in both plant growth and stress responses. However, their impact on the secondary metabolites of woody plants remains elusive. Here, we found that exogenous strigolactone analogue GR24 positively regulates tea plant flavor secondary metabolites, concurrently inhibiting caffeine biosynthesis and promoting the accumulation of caffeine catabolic pathway products. In this process, SL directly or indirectly inhibits the expression of CsSAMSs by inducing CsbHLH80, thereby reducing caffeine biosynthesis. Furthermore, CsbHLH80 enhances caffeine degradation, leading to increased allantoin. Under normal conditions, heightened allantoin reduces abscisic acid (ABA) accumulation. This inhibition reverses under drought stress. Increased ABA significantly enhances tea plant tolerance to both drought and Phyllosticta theicola Petch. In summary, this study offers novel insights for improving tea plant adaptation and quality in arid regions, particularly emphasizing the selection of stress-tolerant varieties and the refinement of production measures with a focus on high-quality production and environmentally friendly biological control methods.

Magnesium chelatase catalysis the insertion of magnesium into protoporphyrin IX is a vital step in chlorophyll biogenesis. It consists of three subunits, CHLI, CHLD and CHLH. The CHLI subunit is an ATPase and hydrolysis ATP in the catalysis. However, its key point on influencing flavonoid biosynthesis and chlorophyll accumulation under different light density was still unknown. In this study, we identified an N-Ethyl-N-nitrosourea (ENU) mutant, p240 from strawberry Fragaria pentaphylla that has yellow-green leaves and lower chlorophyll level. We verified the mutation occurs in the 186th amino acid of CHLI subunit, which is conserved in most photosynthetic organism. Mutants generated from RNAi and CRISPR/Cas9 gene editing confirmed this phenotype. In addition, we found that FpCHLI was localized in chloroplast and its subcellular location have not been changed by mutation. Further study showed that the interaction between FpCHLI and FpCHLD were not affected by mutagenesis. In contrast, all types of mutants showed reduced ATPase and magnesium chelatase activity indicating mutagenesis decreased enzymatic activities. Furthermore, mutagenesis suppressed the biosynthesis of Mg-proto IX. Metabolites analysis of gene knock-out mutant and WT revealed that CHLI may help to keep stabilizing the flavonoid level in leaves. Furthermore, both p240 and chli mutants are light sensitive, which has yellow leaves under high light but pale green leaves under poor light. The photosynthesis ability of mutants was also increased under shade. Moreover, stomatal apertures of mutants were wider than WT. Taken together, these results suggest that CHLI plays an important role in both leaf coloration and metabolism.

Tea anthracnose is a prevalent disease in China that can lead to reduced tea production and lower quality, yet there is currently a lack of effective means for controlling this disease. In this study, we identified 46 phenolamides (including 27 isomers) in different tissues and organs of tea plants based on a developed workflow, and the secondary mass spectra of all these compounds have been documented. It was revealed that tea plants predominantly accumulate protonated aliphatic phenolamides, rather than aromatic phenolamides. The profile of phenolamides indicate that their buildup in tea plants is specific to certain tissues and acyl-acceptors, and this distribution is associated with the extent of phenolamide acyl-modification. Additionally, it was observed that N-Feruloylputrescine (Fer-Put, a type of phenolamides) was responsive to the stimulated accumulation of the tea anthracnose pathogen. The findings of anti-anthracnose experiments in vitro and on tea leaf demonstrated that Fer-Put was capable of significantly inhibiting the growth of anthracnose pathogen colony, effectively prevented tea leaf disease. Furthermore, it was observed that Fer-Put treatment can enhance the antioxidant enzyme activity of tea leaves. TEA002780.1 and TEA013165.1 gene may be responsible for the biosynthesis of Fer-Put in the disease resistance process in tea plants. Through these studies, the types and distribution of phenolamides in tea plants have been elucidated, and Fer-Put's ability to resist anthracnose has been established, providing new insights into the resistance of tea anthracnose.

ABSTRACT The tea green leafhopper, Matsumurasca onukii Matsuda, is the most destructive insect pest of tea plantations in East Asia. While several microbes in M. onukii have been characterized, the microbial community compositions in wild M. onukii populations and the environmental factors that shape them are mostly unknown. In this study, M. onukii populations were collected from major tea growing regions in China. Following high-throughput sequencing of 16S rRNA gene fragments for bacteria and the internal transcribed spacer region for fungi, association analyses were performed within the microbial communities associated with M. onukii and their environmental drivers. We found that the bacterial community structures differed in various regions, and the abundance of dominant bacteria such as Wolbachia, Pseudomonas, Acinetobacter, Pantoea, Enterobacter, and Methylobacterium varied widely. Moreover, wild populations of M. onukii can be infected with facultative symbionts from six genera (Wolbachia, Rickettsia, Asaia, Serratia, Arsenophonus, and Cardinium) with divergent relative abundances. Correlation analysis indicated that altitude was a key environmental factor that shaped bacterial communities of M. onukii. Furthermore, longitude, temperature, and rainfall are also significantly correlated with the bacterial communities. The fungal communities of M. onukii populations were dominated by Ascomycota and Basidiomycota, of which most genera are considered to be plant endophytes or plant pathogens, such as Cladosporium, Fusarium, Alternaria, and Gibberella. We demonstrated that M. onukii carry a complex and variable microbial community, which is influenced by altitude as well as climate-related factors. Our results provide novel insights into the bacteria and fungi of M. onukii. IMPORTANCE Host-associated microbial communities play an important role in the fitness of insect hosts. However, the factors shaping microbial communities in wild populations, including environmental factors and interactions among microbial species, remain largely unknown. The tea green leafhopper has a wide geographical distribution and is highly adaptable, providing a suitable model for studying the effect of ecological drivers on microbiomes. This is the first large-scale culture-independent study investigating the microbial communities of M. onukii sampled from different locations. Altitude as a key environmental factor may have shaped microbial communities of M. onukii by affecting the relative abundance of endosymbionts, especially Wolbachia. The results of this study, therefore, offer not only an in-depth view of the microbial diversity of this species but also an insight into the influence of environmental factors.

Magnesium (Mg2+), as the central atom of chlorophyll, is the most abundant divalent cation for plant growth and development in living cells. MRS2/MGT magnesium transporters play important roles in coping with magnesium stress, chloroplast development and photosynthesis. However, the molecular mechanism of MGT influencing tea plant leaf vein color remains unknown. Here, we demonstrate that CsMGT10 may be a potential transporter influencing leaf vein color. CsMGT10 belongs to Clade A member of MRS2/MGT family. CsMGT10 has the highest expression level in leaves of tea plants. And it is mainly expressed in aboveground parts, especially in vascular bundles. Moreover, CsMGT10 localizes to the chloroplast envelope of tea plants with a high affinity to Mg2+. And the GMN motif is required for its magnesium transport function. Ectopic expression of CsMGT10 in Arabidopsis leaf variegation mutant var5-1 can restore green color of chlorosis leaf veins, and the contents of chlorophyll and carotenoid change significantly, proving its essential role in leaf vein greening. Furthermore, the chlorophyll and carotenoid of tea leaves treated with CsMGT10 antisense oligonucleotides also decrease significantly. Our findings indicate that CsMGT10 mainly acts as Mg2+ transporter in chloroplast envelope of leaf veins, which may play a key role in leaf vein greening of tea plants.

As a common abiotic stress, drought severely impairs the growth, development, and even survival of plants. Here we report a transcription factor, Caragana korshinskii REVOLUTA(CkREV), which can bidirectionally regulate the expression of the critical enzyme gene CkYUC5 in auxin synthesis according to external environment changes, so as to control the biosynthesis of auxin and further enhance the drought resistance of plants. Quantitative analysis reveals that the expression level of both CkYUC5 and AtYUC5 is down-regulated after C. korshinskii and Arabidopsis thaliana are exposed to drought. Functional verification of CkREV reveals that CkREV up-regulates the expression of AtYUC5 in transgenic A. thaliana under common conditions, while down-regulating it under drought conditions. Meanwhile, the expression of CkYUC5 is also down-regulated in C. korshinskii leaves instantaneously overexpressing CkREV. We apply a dual-luciferase reporter system to discover that CkREV can bind to the promoter of CkYUC5 to regulate its expression, which is further proved by EMSA and Y1H esxperiments. Functional verification of CkREV in C. korshinskii and transgenic A. thaliana shows that CkREV can regulate the expression of CkYUC5 and AtYUC5 in a contrary way, maintaining the equilibrium of plants between growth and drought resisting. CkREV can positively regulate the expression of CkYUC5 to promote auxin synthesis in favor of growth under normal development. However, CkREV can also respond to external signals and negatively regulate the expression of CkYUC5, which inhibits auxin synthesis in order to reduce growth rate, lower water demands, and eventually improve the drought resistance of plants.