Abstract
Arthrospira (Spirulina) platensis (ASP) is a representative filamentous, non-N2-fixing cyanobacterium that has great potential to enhance the food supply and possesses several valuable physiological features. ASP tolerates high and low temperatures along with highly alkaline and salty environments, and can strongly resist oxidation and irradiation. Based on genomic sequencing of ASP, we compared the protein expression profiles of this organism under different temperature conditions (15°C, 35°Cand 45°C) using 2-DE and peptide mass fingerprinting techniques. A total of 122 proteins having a significant differential expression response to temperature were retrieved. Of the positively expressed proteins, the homologies of 116 ASP proteins were found in Arthrospira (81 proteins in Arthrospira platensis str. Paraca and 35 in Arthrospira maxima CS-328). The other 6 proteins have high homology with other microorganisms. We classified the 122 differentially expressed positive proteins into 14 functions using the COG database, and characterized their respective KEGG metabolism pathways. The results demonstrated that these differentially expressed proteins are mainly involved in post-translational modification (protein turnover, chaperones), energy metabolism (photosynthesis, respiratory electron transport), translation (ribosomal structure and biogenesis) and carbohydrate transport and metabolism. Others proteins were related to amino acid transport and metabolism, cell envelope biogenesis, coenzyme metabolism and signal transduction mechanisms. Results implied that these proteins can perform predictable roles in rendering ASP resistance against low and high temperatures. Subsequently, we determined the transcription level of 38 genes in vivo in response to temperature and identified them by qRT-PCR. We found that the 26 differentially expressed proteins, representing 68.4% of the total target genes, maintained consistency between transcription and translation levels. The remaining 12 genes showed inconsistent protein expression with transcription level and accounted for 31.6% of the total target genes.
Highlights
Arthrospira (Spirulina) platensis (ASP) is a genera of filamentous, non-heterocyst-forming cyanobacteria
ASP possesses abundant proteins representing 60-70% of its dry weight and its protein composition is nearly perfect for human nutrition
The proteins were sedimented by trichloroacetic acid (TCA)/cold acetone, which inhibited protein hydrolysis due to the presence of protease and removed a large proportion of secondary metabolites, such as pigments, quinones and phenols
Summary
Arthrospira (Spirulina) platensis (ASP) is a genera of filamentous, non-heterocyst-forming cyanobacteria. It is gramnegative, has no flagellum and contains chlorophyll-a that carries out photosynthesis producing oxygen. ASP possesses abundant proteins representing 60-70% of its dry weight and its protein composition is nearly perfect for human nutrition. It contains eight necessary amino acids, various unsaturated fatty acids, vitamins, mineral substances and biologically active agents which are necessary for the human body. These substances provide increased immunity, anti-cancer and antiaging benefits, radiation resistance, antioxidant properties, and reduction to drug toxicity effects. ASP is widely applied to several fields, such as functional food, compound feedstuff, new model medicines and fine chemicals [2]
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