De novo transcriptome of the diatom Cylindrotheca closterium identifies genes involved in the metabolism of anti-inflammatory compounds

Abstract

Diatoms are the most diverse and abundant group of phytoplankton species and represent a huge reservoir of marine natural products with possible application for human health. Several diatoms are known to have anticancer, anti-inflammatory, antioxidant and anti-microbial properties, but the compounds responsible of these activities are often still unknown. The diatom Cylindrotheca closterium showed anti-inflammatory properties inhibiting TNFα release in human monocytic leukemia cells. In this study, we present the full transcriptome of C. closterium, and used an -omic approach to identify transcripts coding enzymes that can be involved in the synthesis/degradation of anti-inflammatory compounds. This approach allowed to identify phosphatidylinositol-3phosphatase, phosphatidylinositol 3-kinase catalytic subunit type 3, phosphatidylinositol N-acetylglucosaminyltransferase subunit A, monogalactosyldiacylglycerol synthase and violaxanthin de-epoxidase, which are known to be involved in anti-inflammatory compound metabolism. When C. closterium was cultured in silica-starvation conditions, selected as stress condition to potentially trigger the synthesis of bioactive metabolites, anti-inflammatory activity was lost and expression levels of the analyzed transcripts were reduced. These data suggested that the control culturing condition was the most active. This study used for the first time a transcriptomic-guided approach to identify enzymes involved in anti-inflammatory compound metabolism, directing future discoveries of marine natural products in microalgae.Diatoms are the most diverse group of phytoplankton with an estimation of 200,000 different species 1 . Their diversity offers an enormous reservoir of new compounds with possible biotechnological applications 2 . Throughout the last decades, enhancement in the multi-omics methodologies (such as genomics, transcriptomics, proteomics and metabolomics) lead to exploration and exploitation of diatom properties, supporting the identification and characterization of new marine natural products and enzymes with possible applications in the blue biotechnology field 2-6 . Diatoms have been already shown to have antioxidant 7 , anti-diabetes 8 , anticancer 9 , antibacterial 7,10

De novo Transcriptome of the Non-saxitoxin Producing Alexandrium tamutum Reveals New Insights on Harmful Dinoflagellates

“…Initial cell concentration for each bottle was about 5000 cells/mL. Culture growth was monitored daily by sampling 2 mL of culture, and fixing with one drop of Lugol (final concentration of about 2%, v / v ) and counting cell numbers in a Bürker counting chamber under an Axioskop 2 microscope (20×) (Carl Zeiss GmbH, Oberkochen, Germany) (as in Elagoz et al [ 108 ]). The growth curve of Alexandrium tamutum (in control and P-starvation conditions) is available in Figure S3 .…”

“…Experimental culturing for both control and P-starvation conditions was performed in 2 litre polycarbonate bottles (each condition was performed in biological triplicates), constantly bubbled with air filtered through 0.2 µm membrane filters. For the control condition, normal K medium was used, while for the P-starvation experiment, the K medium was prepared with low concentrations of phosphate (0.5 µM PO 4 2− rather than 36 µM PO 4 2− of the control condition [108]). The growth curve of Alexandrium tamutum (in control and P-starvation conditions) is available in Figure S3.…”

Pheophorbide a: State of the Art

“…Recent studies showed that microalgae produce metabolites with anticancer [5], anti-inflammatory [6], anti-diabetes [7], antioxidant [8], anti-tuberculosis [9], anti-epilepsy [10], anti-hypertensive [8], anti-atherosclerosis [8] anti-osteoporosis [8] and immunomodulatory activities [11,12]. In addition, various authors showed that different nutrient culturing conditions could influence microalgae bioactivities [6,13], triggering the activation of specific metabolic pathways [14][15][16][17]. These studies showed that the bioactivity of microalgae is not correlated with a specific microalgae class or a specific culturing condition, but depends on the microalgae clone, the algal growth phase, the culturing condition and chemical extraction protocol used, and should be carefully considered case by case.…”

In Silico Identification of Type III PKS Chalcone and Stilbene Synthase Homologs in Marine Photosynthetic Organisms

“…They are also known to produce a plethora of metabolites derived from primary and secondary metabolism, which have shown possible applications for human health (e.g., compounds with anti-cancer, anti-microbial, anti-diabetes, anti-epilepsy, anti-inflammatory, anti-atherosclerosis, anti-osteoporosis, immunomodulatory and antioxidant activities; [1][2][3][4][5][6][7][8][9][10]). Various studies have focused on the discovery of metabolic pathways involved in the synthesis of bioactive compounds [11][12][13][14]. Even if microalgae can be cultured in big volumes to get large amounts of the compounds of interest, heterologous expression of the enzyme responsible for the compound synthesis and its production in a host can be a valuable alternative for meeting industrial demands.…”