Abstract
Transcription factors control many processes in plants and have high potentials to manipulate specialized metabolic pathways. Transcriptional regulation of the biosynthesis of monoterpenoid indole alkaloids (MIAs), nicotine alkaloids, and benzylisoquinoline alkaloids (BIAs) has been characterized using Catharanthus roseus, Nicotiana and Coptis plants. However, metabolic engineering in which specific transcription factors are used in alkaloid biosynthesis is limited. In this study, we characterized the effects of ectopic expression of CjWRKY1, which is a transcriptional activator with many targets in BIA biosynthesis in Coptis japonica (Ranunculaceae) and Eschscholzia californica (California poppy, Papaveraceae). Heterologous expression of CjWRKY1 in cultured California poppy cells induced increases in transcripts of several genes encoding BIA biosynthetic enzymes. Metabolite analyses indicated that the overexpression of the CjWRKY1 gene also induced increases in the accumulation of BIAs such as sanguinarine, chelerythrine, chelirubine, protopine, allocryptopine, and 10-hydroxychelerythrine in the culture medium. Previous characterization of EcbHLH1 and current results indicated that both transcription factors, WRKY1 and bHLH1, are substantially involved in the regulation of BIA biosynthesis. We discuss the function of CjWRKY1 in E. californica cells and its potential for metabolic engineering in BIA biosynthesis.
Highlights
IntroductionAlkaloids, which are nitrogen-containing compounds, are found in approximately 20% of plant species and often used as important pharmaceuticals, stimulants, and narcotics because of their strong biological activities [1]
Plants produce structurally divergent, low molecular weight specialized secondary metabolites
Effects of overexpression of the CjWRKY1 gene as a transcriptional activator of benzylisoquinoline alkaloids (BIAs) biosynthesis were examined in heterologous California poppy cells
Summary
Alkaloids, which are nitrogen-containing compounds, are found in approximately 20% of plant species and often used as important pharmaceuticals, stimulants, and narcotics because of their strong biological activities [1]. Despite their usefulness, information on the biosynthetic pathways of alkaloids is very limited to specific plant species. We focus on BIAs, because they are among the most diverse alkaloids, with approximately 2500 natural product structures [6].
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