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Updated: Jul 1, 2026

Measuring Gene Expression in Bombarded Barley Aleurone Layers with Increased Throughput
Published on: March 30, 2018
The R2R3-MYB transcription factor ApMYB9 links UV-B signaling to andrographolide biosynthesis by activating ApIPPI in
Jingyu Li1, Shiqiang Xu1, Mingyang Sun1
1Guangdong Provincial Key Laboratory of Crops Genetics and Improvement, Crop Research Institute, Guangdong Academy of Agriculture Sciences, Guangzhou, 510640, China; Guangdong Provincial Engineering & Technology Research Center for Conservation and Utilization of the Genuine Southern Medicinal Resources, Guangzhou, 510640, China.
Abstract:
Andrographis paniculata, a medicinal species within the Acanthaceae family, is widely recognized as a "traditional Chinese herbal antibiotic," with andrographolides (ADs) serving as its primary bioactive components. Nevertheless, the molecular regulatory mechanisms governing the biosynthesis of ADs remain poorly understood. In this study, Ultraviolet-B (UV-B) radiation significantly induced the expression of ApIPPI, a gene encoding isopentenyl pyrophosphate isomerase, which is correlated with the accumulation of ADs. Sequence analysis revealed that the ApIPPI promoter contains a variety of MYB-binding elements. ApMYB9, a UV-B-responsive R2R3-MYB transcription factor belonging to the S20 subfamily, was identified by a yeast screening library. Subcellular localization and transcriptional activation assays demonstrated that ApMYB9 is localized in the nucleus and exhibits transcriptional activation capabilities. Integrated analyses using yeast one-hybrid (Y1H), dual-luciferase reporter (Dual-LUC) assays, and electrophoretic mobility shift assays (EMSA) confirmed that ApMYB9 targets specific MYB recognition motifs in the ApIPPI promoter to positively regulate its expression. Transient overexpression of ApMYB9 in A. paniculata leaves boosted ApIPPI transcript levels and promoted ADs biosynthesis. This study elucidates a UV-B response regulatory module in which ApMYB9 directly targets the ApIPPI promoter, redirecting metabolic flux to the accumulation of andrographolide. This provides a potential target for metabolic engineering aimed at optimizing the production of bioactive compounds from A. paniculata.
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