Spectral quality as an elicitor of bioactive compound production in Solanum aculeatissimum JACQ cell suspension

https://doi.org/10.1016/j.jphotobiol.2020.111819Get rights and content

Highlights

  • All light conditions resulted in increased biomass and cell viability.

  • The light condition was not a determining factor of phenolic compound production.

  • Bioactive compounds were detected in higher quantities at seven days of culture.

  • The redox process repair mechanism was efficient in the cell cultures.

Abstract

Solanum aculeatissimum Jacq. is a common plant in much of Brazil. Despite containing metabolites with a wide range of pharmacological applications, there are few tissue culture reports for this plant. The possibility of large-scale in vitro production of this material has significant biotechnological potential. Therefore, the objective of this study was to investigate the effect of light conditions on the growth of cells in suspension, observing the production and yield of biomass and bioactive compounds and the enzymatic behavior. Calli obtained from leaf segments were cultured in solid medium supplemented with 1 mg L−1 of 2,4-D, 2.5 mg L−1 kinetin, pH 5.7, in the dark. After 110 days of subculture, the calli were transferred to liquid medium. Cells were kept in the dark under agitation at 110 rpm and 25 °C and subcultured every 30 days. After 90 days of culture, 20 mL aliquots of cell suspension were added to flasks containing approximately 20 mL of medium (1:1) and cultured at different wavelengths (white, green, blue, red, and blue/red) under a photoperiod of 16 h with irradiance of 50 μmol m−2 s−1) and in the absence of light. The experiment was performed in a 6 × 6 factorial design (light condition × culture time). The cell cultures showed viability throughout the entire cycle, and chlorogenic and ferulic acids, orientin, quercitrin and, in higher amounts, quercetin, were detected in the first 7 days of culture. There was an increase in superoxide dismutase and catalase and a decrease in ascorbate peroxidase after exposure to different light conditions; for phenylalanine ammonia lyase, no differences were observed. The different light conditions were not sufficient to trigger responses in the concentrations of bioactive compounds, despite the detection of increased levels of the enzymes involved in cellular homeostasis.

Introduction

Solanum aculeatissimum Jacq. is present in tropical and subtropical regions in much of the world, and South America is the center of diversity and distribution of this species [1]. The Solanum genus has abundant bioactive metabolites in various parts of the plant, such as groups of steroidal alkaloids, pyridines, withanolides, sesquiterpenes and diterpenes, glycoalkaloids and flavonoids, among others, and this species can be a source of numerous compounds used for medicinal purposes with cytotoxic, antifungal and antitumor effects [2,3].

The potential of using cell culture for the production and accumulation of chemical compounds with the same bioactivity of the mother plant has been known since the emergence of tissue culture techniques [4]. Sustainable cell cultures are a promising way to achieve a continuous, large-scale supply of compounds of interest because they have the flexibility to produce plant material anywhere in the world, regardless of the geographic or environmental conditions, and are free of microbiological and chemical contamination, with rapid and safe growth cycles [5,6].

Despite these advantages, there are few reports of commercial plant cell culture biofactories due to insufficient information about the metabolic pathways of the compounds of interest. This culture method has the potential to investigate various elicitation processes, avoiding or detecting possible interfering compounds through physiological and biochemical processes, in addition to providing valuable information that enables the screening of metabolically produced compounds [6]. Much of the difficulty related to the use of new light-based methods is the lack of available literature on the subject, in addition to a lack of information on the types of lamps to be used, such as fluorescent or LED, hindering the reproduction of the method in other species [7].

Spectral condition, photon flux and photoperiod are the main triggers for plant growth and development. Light-emitting diode (LED) technology has been recently used in several studies on micropropagation, both in vitro and ex vitro, being considered a great alternative light source, with an efficient emission of a certain radiation [6,8]. The advantages of LED lamps are low power consumption and a longer service life. A large part of the supplied energy is converted as desired, with minimal heat production and high energy efficiency, and they are able to emit light at the desired colour without the need to use filters, as is the case in a traditional fluorescent lamp [8].

By subjecting the plant to severe stress, the cells can accumulate reactive oxygen species (ROS). Exposure to several external biotic or abiotic stress factors triggers the biosynthesis of substances involved in cellular redox homeostasis, such as the enzymes superoxide dismutase, catalase, ascorbate peroxidase and phenylalanine ammonia lyase [9]. However, when there is excessive production of ROS, the cell function is impaired by the oxidative stress that is generated, which has several adverse effects, such as enzymatic oxidation, membrane lipid peroxidation and DNA damage [10].

The objective of this study was to detect and quantify bioactive compounds of biotechnological interest in S. aculeatissimum and to analyze the regulatory behavior of the enzymes associated with oxidative stress that are generated by exposure to different light conditions. If substantial production of bioactive compounds of biological and pharmacological importance are observed, the study will provide relevant information on the biochemical response, in addition to preliminary data on the production yield an industrial scale.

Section snippets

Materials and Methods

The experiments were conducted at the Laboratory of Plant Tissue Culture of the Federal Institute of Education, Science and Technology Goiano (IF Goiano) - Rio Verde Campus, State of Goiás (GO), Brazil. Approximately 200 ripe fruits of S. aculeatissimum were collected from plants located in the municipality of Rio Verde, at coordinates 17° 48′ 343” S - 50° 54′ 00” W, altitude 616 m. After collection, the fruits were pulped to remove the seeds and subsequently dried at 35 °C in a forced air oven.

Biometric Evaluations and Cell Viability Monitoring

Independent of the light condition applied to the in vitro culture, the suspensions exhibited a linear increase in fresh and dry weight as a function of culture time, reaching 10.48 g and 0.64 g, respectively (Fig. 2A and B). At 35 days, a higher dry biomass was observed when cells were cultured under blue/red light, reaching 0.70 g (Fig. 3). The increase in biomass production in suspension cultures is promoted by an appropriate balance between the auxin and cytokinin concentrations in cell

Conclusion

Regardless of the light condition, S. aculeatissimum cell cultures showed viability throughout the cycle, and metabolites with biotechnological applications were detected, such as chlorogenic and ferulic acids, orientin, quercitrin and, in greater amounts, quercetin, especially until up to 7 days of culture.

There was an increase in SOD and CAT activity and a decrease in APX activity regardless of the light condition throughout the entire in vitro culture; however, there was no difference in

Authors Contributions

Fabiano and Paulo was responsible for funding acquisition; Luciana, Márcio and Ana did the original draft; Writing – review & editing and performed the experiments; Luciana, Erika and Paulo did Supervision; Validation and performed the chromatographic analyzes; Luciana and Márcio performed enzymatic analyzes; Luciana, Aurélio, Fabiano and Fernando contributed to Project administration; Resources; Software; Supervision of the research and to the writing of the paper.

Declaration of Competing Interest

The authors declare that they have no conflict of interest.

Acknowledgements

We thank the Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES), the National Council for Scientific and Technological Development (CNPq), the Goiás Research Foundation (FAPEG), the Pro-Centro Oeste Network and the Federal Institute of Education, Science and Technology Goiano (IF Goiano) for their support.

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