Small-Scale Bioreactor for Sterile Hydroponics and Hairy Roots: Metabolic Diversity and Salicylic Acid Exudation by Hairy Roots of Hyoscyamus niger

Zana Jamal Kareem,Anke Sirrenberg,Ahmad Hama Ameen H Rashid,Anna Rathgeb,Ling Su,Franz Hadacek,Petr Karlovsky

doi:10.3390/app9153044

Zana Jamal Kareem, Anke Sirrenberg + Show 5 more

Open Access

https://doi.org/10.3390/app9153044

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Abstract

The volume and complexity of commercial bioreactors for sterile hydroponics and hairy roots are too large for comparative analysis of many cultures. Here a small-scale bioreactor fabricated from standard glass materials and suitable for both airlift and bubble aeration mode is described. The performance of the bioreactor was tested by growing oilseed rape (Brassica napus L.) and rose plants (Rosa canina L.) in sterile hydroponics and by cultivating hairy roots of henbane (Hyoscyamus niger L.) and sesame (Hyoscyamus niger L.). Plants grown in hydroponics for up to six weeks did not show chloroses or necroses. Hairy roots grew faster or comparably fast in bioreactors as compared to shaking flasks. Root exudates of roses and exudates of hairy roots of henbane were subjected to targeted and nontargeted analysis by HPLC coupled with optical and mass spectrometric detectors. The diversity and concentration of hairy root exudates were higher in bioreactors than in shaking flasks. The composition of hairy root exudates of three accessions of H. niger did not match the genetic relatedness among the accessions. Hairy roots of Hyoscyamus niger exuded salicylic acid in amounts varying among plant accessions and between bioreactors and shaking flask cultures.

Highlights

Roots of land plants exude small molecules, oligosaccharides, and proteins into the soil.The secreted compounds called root exudates serve multiple functions: they facilitate mobilization of soil nutrients [1,2,3], modulate the composition of microbial communities of the rhizosphere [4], and attract or repel soil micro- and mesofauna, affecting crop health and productivity [5]
Hairy roots are plant roots genetically transformed with the help of Agrobacterium rhizogenes that exhibit neoplastic growth and can be maintained indefinitely in sterile media without externally added phytohormones [12,13]
Biomass production in hairy root cultures is higher than in callus or suspension cultures, hairy roots have been exploited for the production of plant secondary metabolites [12,19,20,21,22]

Summary

Introduction

Roots of land plants exude small molecules, oligosaccharides, and proteins into the soil.The secreted compounds called root exudates serve multiple functions: they facilitate mobilization of soil nutrients [1,2,3], modulate the composition of microbial communities of the rhizosphere [4], and attract or repel soil micro- and mesofauna, affecting crop health and productivity [5]. Exudation of metabolites by roots is modulated by nutrient availability [6] and herbivore infestation [7]. Hairy roots proved useful in studies of interactions between crop plants and herbivores [18]. Biomass production in hairy root cultures is higher than in callus or suspension cultures, hairy roots have been exploited for the production of plant secondary metabolites [12,19,20,21,22].

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