Tempo-Spatial Pattern of Stepharine Accumulation in Stephania Glabra Morphogenic Tissues.

Tatiana Gorpenchenko,Victor Bulgakov,Valeria Grigorchuk,Dmitry Bulgakov,Galina Tchernoded

doi:10.3390/ijms20040808

Abstract

Alkaloids attract great attention due to their valuable therapeutic properties. Stepharine, an aporphine alkaloid of Stephania glabra plants, exhibits anti-aging, anti-hypertensive, and anti-viral effects. The distribution of aporphine alkaloids in cell cultures, as well as whole plants is unknown, which hampers the development of bioengineering strategies toward enhancing their production. The spatial distribution of stepharine in cell culture models, plantlets, and mature micropropagated plants was investigated at the cellular and organ levels. Stepharine biosynthesis was found to be highly spatially and temporally regulated during plant development. We proposed that self-intoxication is the most likely reason for the failure of the induction of alkaloid biosynthesis in cell cultures. During somatic embryo development, the toxic load of alkaloids inside the cells increased. Only specialized cell sites such as vascular tissues with companion cells (VT cells), laticifers, and parenchymal cells with inclusions (PI cells) can tolerate the accumulation of alkaloids, and thus circumvent this restriction. S. glabra plants have adapted to toxic pressure by forming an additional transport secretory (laticifer) system and depository PI cells. Postembryonic growth restricts specialized cell site formation during organ development. Future bioengineering strategies should include cultures enriched in the specific cells identified in this study.

Highlights

Alkaloid-producing plants have developed effective coping strategies inherent to secondary metabolism, including competition for resources, metabolic imbalance, and potential self-intoxication [1]
Efforts to improve the yield of alkaloids from cell cultures have focused on feeding precursors or over-expressing the transcription factors and enzymes positioned at metabolic bottlenecks; they have largely only resulted in modest improvements in yield [2,3,4]
Because equal amounts of stepharine were found in SEs and roots at the later stages of development, we propose that stepharine accumulation depends on the quantity and proportion of the specific PI and VT cells (Figure S3)

Summary

Introduction

Alkaloid-producing plants have developed effective coping strategies inherent to secondary metabolism, including competition for resources, metabolic imbalance, and potential self-intoxication [1]. Effective metabolic engineering approaches are often obscured by limitations in our knowledge of alkaloid biosynthesis regulation. Systems biology approaches in terms of secondary metabolism are developing slowly, especially for proteomics and bioinformatics studies of the relationship between protein regulation of secondary metabolism and the modules that determine the stem cell specification, embryogenesis, plant development, and tissue differentiation in general. In this respect, investigation into the general rules and specificity of the spatial-temporal regulation of biosynthetic pathways is of high importance

Methods

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Discussion

Conclusion