Uniconazole is a triazole plant growth regulator that is widely used to regulate plant height and prevent seedling overgrowth. However, the molecular mechanism by which uniconazole inhibits seedling hypocotyl elongation is still unclear, and there are only a few studies that combine transcriptome and metabolome data to investigate the mechanism of hypocotyl elongation. Here, we observed that uniconazole significantly inhibited hypocotyl elongation in Chinese flowering cabbage seedlings. Interestingly, based on the combined transcriptome and metabolome analysis, we found that uniconazole significantly affected the “phenylpropanoid biosynthesis” pathway. In this pathway, only one gene of the enzyme regulatory gene family, BrPAL4, which is involved in lignin biosynthesis, was significantly downregulated. In addition, yeast one-hybrid and two-hybrid assays demonstrated that BrbZIP39 could directly bind to the promoter region of BrPAL4 and activate its transcription. The virus-induced gene silencing system further proved that BrbZIP39 could positively regulate hypocotyl elongation of Chinese cabbage and hypocotyl lignin synthesis. The results of this study provide new insights into the molecular regulatory mechanism of cloconazole in inhibiting hypocotyl elongation of Chinese cabbage. It was confirmed for the first time that cloconazole reduced lignin content by inhibiting phenylpropanoid synthesis mediated by BrbZIP39-BrPAL4 module, thereby leading to hypocotyl dwarfing in Chinese cabbage seedlings.
Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) belongs to the genus Brassica and is a well-known annual cruciferous vegetable widely grown in my country (Wang et al., 2022; Yue et al., 2022). In recent years, the production scale of Chinese cauliflower has continued to expand, and the cultivation method has changed from the traditional direct seeding to intensive seedling culture and transplantation. However, in the process of intensive seedling culture and transplantation, excessive hypocotyl growth tends to produce leggy seedlings, resulting in poor seedling quality. Therefore, controlling excessive hypocotyl growth is a pressing issue in intensive seedling culture and transplantation of Chinese cabbage. Currently, there are few studies integrating transcriptomics and metabolomics data to explore the mechanism of hypocotyl elongation. The molecular mechanism by which chlorantazole regulates hypocotyl expansion in Chinese cabbage has not yet been studied. We aimed to identify which genes and molecular pathways respond to uniconazole-induced hypocotyl dwarfing in Chinese cabbage. Using transcriptome and metabolomic analyses, as well as yeast one-hybrid analysis, dual luciferase assay, and virus-induced gene silencing (VIGS) assay, we found that uniconazole could induce hypocotyl dwarfing in Chinese cabbage by inhibiting lignin biosynthesis in Chinese cabbage seedlings. Our results provide new insights into the molecular regulatory mechanism by which uniconazole inhibits hypocotyl elongation in Chinese cabbage through inhibiting phenylpropanoid biosynthesis mediated by the BrbZIP39–BrPAL4 module. These results may have important practical implications for improving the quality of commercial seedlings and contributing to ensuring the yield and quality of vegetables.
The full-length BrbZIP39 ORF was inserted into pGreenll 62-SK to generate the effector, and the BrPAL4 promoter fragment was fused to the pGreenll 0800 luciferase (LUC) reporter gene to generate the reporter gene. The effector and reporter gene vectors were co-transformed into tobacco (Nicotiana benthamiana) leaves.
To clarify the relationships of metabolites and genes, we performed a joint metabolome and transcriptome analysis. KEGG pathway enrichment analysis showed that DEGs and DAMs were co-enriched in 33 KEGG pathways (Figure 5A). Among them, the “phenylpropanoid biosynthesis” pathway was the most significantly enriched; the “photosynthetic carbon fixation” pathway, the “flavonoid biosynthesis” pathway, the “pentose-glucuronic acid interconversion” pathway, the “tryptophan metabolism” pathway, and the “starch-sucrose metabolism” pathway were also significantly enriched. The heat clustering map (Figure 5B) showed that the DAMs associated with DEGs were divided into several categories, among which flavonoids were the largest category, indicating that the “phenylpropanoid biosynthesis” pathway played a crucial role in hypocotyl dwarfism.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Post time: Mar-24-2025