Long non-coding RNA lnc87821 negatively regulates CsJAZ2 to modulate salt and alkali stress responses in Camellia sinensis

Tea plant (Camellia sinensis [L.] O. Kuntze), a major economic crop in China, is an acidophilic species with stringent requirements for its growth environment. Soil salinization is increasingly threatening the sustainable cultivation of tea plant. However, the lncRNA-mediated regulatory mechanisms underlying salt and alkali stress tolerance remain largely elusive. Based on our preliminary research, a long non-coding RNA (lncRNA) in tea plant, lnc87821, was predicted to potentially cis-regulate its downstream target gene CsJAZ2, and respond to salt stress. Therefore, this study aimed to experimentally validate the lnc87821-CsJAZ2 regulatory relationship. By integrating gene cloning, expression analysis, coding potential prediction, GUS reporter assays, and gene silencing in tea shoots, we elucidated the negative regulatory role of lnc87821 on CsJAZ2, and confirmed its functional relevance under salt and alkali stresses. Under these conditions, the expression of lnc87821 and CsJAZ2 exhibited significant negative correlations. Silencing lnc87821 in tea shoots significantly upregulated the expression of CsJAZ2 and downstream antioxidant-related genes. Furthermore, CsJAZ2 enhanced the scavenging capacity of reactive oxygen species (ROS) under salt and alkali stresses. Furthermore, bioinformatic promoter analysis of CsJAZ2 suggested that lnc87821 might modulate CsJAZ2 transcription by interfering with the binding of transcription factors to the G-box and ABRE cis-acting elements. Our results demonstrate that lnc87821 functions as a negative regulator in tea plant tolerance to salt and alkali stresses by modulating CsJAZ2. This study provides novel insights into the stress adaptation mechanisms of tea plant and identifies candidate genes for molecular breeding for stress resistance.