Abstract：Indolic glucosinolates (IGS) play a crucial role in plant pathogen defense responses, MYB (myeloblastosis) 34, MYB51 and MYB122 are 3 important transcription factors that regulate indolic glucosinolate biosynthesis. This study systematically studied the temporal and spatial expression patterns of 3 transcription factor genes and their responses to hormones, which could provide data for further study on the disease resistance mechanism of indolic glucosinolates. Using Arabidopsis thaliana genomic DNA as a template, the promoter sequences of MYB34, MYB51 and MYB122 genes were amplified, plant expression vectors with GUS (β-glucuronidase coding gene) expression driven by the promoters of MYB34, MYB51, and MYB122, respectively were constructed and transferred into Arabidopsis thaliana. PMYB34::GUS, PMYB51::GUS and PMYB122::GUS transgenic lines were confirmed. Through the detection of GUS activity, the temporal and spatial expression patterns of 3 genes and the response to several hormones were analyzed. Gene expression analysis showed that the temporal and spatial expression patterns of MYB34, MYB51 and MYB122 genes were similar. All the 3 genes generally expressed in various stages of growth and development and in various tissues, in the cotyledons, hypocotyls and radicles of seedlings, and the vascular bundles of roots, stems, leaves, flowers, and pods of mature plants. However, the 3 genes showed their own specific expression pattern. The expression of MYB51 performed higher in ground tissue than in root tissue, while the MYB34 and MYB122 were mainly expressed in the roots. Hormone responsiveness analysis showed that MYB51 was induced by salicylic acid (SA) and MYB34 was induced by methyl jasmonate (MeJA). Compared with MYB34 and MYB51, MYB122 was not sensitive to hormone stimulation. Under the experimental conditions of this study, the expression level of MYB122 did not change significantly after several hormone treatments. The above research results suggested that the metabolism of indolic glucosinolates might be regulated by different signaling pathways in different tissues of the plant. This study preliminarily clarified the temporal and spatial expression characteristics of MYB34, MYB51 and MYB122, and provided basic data for further revealing the regulation mechanism of indolic glucosinolate biosynthesis.
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