Chlormequat chloride treatment inhibits grapevine stem growth via the VviRAP2.12 - VviEXPA7 regulatory module

Abstract

Treatment with chlormequat chloride (CCC) can lead to dwarfism, which has been studied in many plants. However, the underlying molecular mechanisms have been less studied. Herein, the phenotypic changes and gene expression levels of grapevine in response to CCC were investigated. Results showed that the height of grape plants became significantly shorter after CCC treatment, especially between the first two stems above the roots. Transcriptome sequencing was then performed and analyzed, 120 differentially expressed genes (DEGs) were detected in the stems after CCC treatment compared to the control. The gene ontology (GO) enrichment results showed that processes such as cellulose synthase (UDP-forming) activity, regulation of the auxin-mediated signaling pathway, and the cellulose biosynthetic process were common. In addition, weighted gene co-expression network analysis (WGCNA) identified the strong correlation between the MEbrown module and stem development. VviEXAP7 was selected from the genes belonging to key GO pathways and WGCNA modules. The quantitative real-time PCR (qRT-PCR) results showed that VviEXPA7 was significantly downregulated because of the CCC treatment. Additionally, analysis of VviEXPA7 promoter activity showed that VviEXPA7 activated GUS gene expression, and was induced by CCC, abscisic acid (ABA), and other hormones. VviEXPA7 was used as a target gene for transcription factor prediction, and after employing the PlantTFDB and JASPAR databases, VviRAP2.12 was identified as a transcription factor that might regulate VviEXPA7. qRT-PCR revealed that VviRAP2.12 was significantly upregulated after CCC treatment. Finally, the interaction between VviEXPA7 and VviRAP2.12 was verified by the dual-luciferase assay. Thus, the current study shows that CCC decreased the expression of the cell growth-related gene VviEXPA7 by promoting the expression of VviRAP2.12, which resulted in dwarfed plants. This study generated new information that will increase our understanding of the mechanism of action of CCC and provides a scientific basis for simplified cultivation of grapes.