(Z)-3-Hexenol integrates drought and cold stress signaling by activating abscisic acid glucosylation in tea plants

Dynamic changes and the effects of key procedures on the characteristic aroma compounds of Lu'an Guapian green tea during the manufacturing process

As a kind of green tea with unique multiple baking processes, the flavor code of Lu'an Guapian (LAGP) has recently been revealed. To improve and stabilize the quality of LAGP, further insight into the dynamic changes in odorants during the whole processing is required. In this study, 50 odorants were identified in processing tea leaves, 14 of which were selected for absolute quantification to profile the effect of processes. The results showed that spreading is crucial for key aroma generation and accumulation, while these odorants undergo significant changes at the deep baking stage. By adjusting the conditions of the spreading and deep baking, it was found that low-temperature (4 °C) spreading for 6 h and low-temperature with long-time baking (final leaf temperature: 102 °C, 45 min) could improve the overall aroma quality. These results provide a new direction for enhancing the quality of LAGP green tea.

CsREV-CsTCP4-CsVND7 module shapes xylem patterns differentially between stem and leaf to enhance tea plant tolerance to drought

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.

Identification and Validation of the miR156 Family Involved in Drought Responses and Tolerance in Tea Plants (Camellia sinensis (L.) O. Kuntze)

The microRNA156 (miR156) family, one of the first miRNA families discovered in plants, plays various important roles in plant growth and resistance to various abiotic stresses. Previously, miR156s were shown to respond to drought stress, but miR156s in tea plants (Camellia sinensis (L.) O. Kuntze) have not been comprehensively identified and analyzed. Herein, we identify 47 mature sequences and 28 precursor sequences in tea plants. Our evolutionary analysis and multiple sequence alignment revealed that csn-miR156s were highly conserved during evolution and that the rates of the csn-miR156 members' evolution were different. The precursor sequences formed typical and stable stem-loop structures. The prediction of cis-acting elements in the CsMIR156s promoter region showed that the CsMIR156s had diverse cis-acting elements; of these, 12 CsMIR156s were found to be drought-responsive elements. The results of reverse transcription quantitative PCR (RT-qPCR) testing showed that csn-miR156 family members respond to drought and demonstrate different expression patterns under the conditions of drought stress. This suggests that csn-miR156 family members may be significantly involved in the response of tea plants to drought stress. Csn-miR156f-2-5p knockdown significantly reduced the Fv/Fm value and chlorophyll content and led to the accumulation of more-reactive oxygen species and proline compared with the control. The results of target gene prediction showed that csn-miR156f-2-5p targeted SQUAMOSA promoter binding protein-like (SPL) genes. Further analyses showed that CsSPL14 was targeted by csn-miR156f-2-5p, as confirmed through RT-qPCR, 5' RLM-RACE, and antisense oligonucleotide validation. Our results demonstrate that csn-miR156f-2-5p and CsSPL14 are involved in drought response and represent a new strategy for increasing drought tolerance via the breeding of tea plants.

Multilayer omics landscape analyses reveal the regulatory responses of tea plants to drought stress

Adverse environments, especially drought conditions, deeply influence plant development and growth in all aspects, and the yield and quality of tea plants are largely dependent on favorable growth conditions. Although tea plant responses to drought stress (DS) have been studied, a comprehensive multilayer epigenetic, transcriptomic, and proteomic investigation of how tea responds to DS is lacking. In this study, we generated DNA methylome, transcriptome, proteome, and phosphoproteome data to explore multiple regulatory landscapes in the tea plant response to DS. An integrated multiomics analysis revealed the response of tea plants to DS at multiple regulatory levels. Furthermore, a set of DS-responsive genes involved in photosynthesis, transmembrane transportation, phytohormone metabolism and signaling, secondary metabolite pathways, transcription factors, protein kinases, posttranslational and epigenetic modification, and other key stress-responsive genes were identified for further functional investigation. These results reveal the multilayer regulatory landscape of the tea plant response to DS and provide insight into the mechanisms of these DS responses.