Arthrospira platensis Mutagenesis for Protein and C-Phycocyanin Improvement and Proteomics Approaches.

Arthrospira (Spirulina) platensis is known for its use as a food supplement, with reported therapeutic properties including antiviral, anti-inflammatory and antioxidant activity. Arthrospira is also an excellent source of proteins and C-phycocyanin. The latter is a light-harvesting pigment-protein complex in cyanobacteria, located on the outer surface of the thylakoid membrane and comprising 40 to 60% of the total soluble protein in cells. Random mutagenesis is a useful tool as a non-genetically modified mutation method that has been widely used to generate mutants of different microorganisms. Exposure of microalgae or cyanobacteria to chemical stimuli affects their growth and many biological processes. Chemicals influence several proteins, including those involved in carbohydrate and energy metabolisms, photosynthesis and stress-related proteins (oxidative stress-reactive oxygen species (ROS) scavenging enzymes). Signal transduction pathways and ion transportation mechanisms are also impacted by chemical treatment, with changes causing the production of numerous biomolecules and stimulation of defence responses. This study compared the protein contents of A. platensis control and after mutagenesis using diethyl sulphate (DES) under various treatment concentrations for effective mutation of A. platensis. Results identified 1152 peptides using proteomics approaches. The proteins were classified into 23 functional categories. Random mutagenesis of A. platensis by DES was found to be highly effective for C-phycocyanin and protein production.

Expression levels of genes involved in metal homeostasis, physiological adaptation, and growth characteristics of rice (Oryza sativa L.) genotypes under Fe and/or Al toxicity.

Acid sulphate soil contains high amounts of iron (Fe) and aluminum (Al), and their contamination has been reported as major problems, especially in rainfed and irrigated lowland paddy fields. Rice is sensitive to Fe and Al grown in acid soil (pH < 5.5), leading to growth inhibition and grain yield loss. The objective of this study was to evaluate Fe and/or Al uptake, translocation, physiological adaptation, metal toxicity, and growth inhibition in rice genotypes grown in acid soil. Fe and Al in the root tissues of all rice genotypes were enriched depending on the exogenous application of either Fe or Al in the soil solution, leading to root growth inhibition, especially in the KDML105 genotype. Expression level of OsYSL1 in KDML105 was increased in relation to metal uptake into root tissues, whereas OsVIT2 was downregulated, leading to Fe (50.3 mg g-1 DW or 13.1 folds over the control) and Al (4.8 mg g-1 DW or 2.2 folds over the control) translocation to leaf tissues. Consequently, leaf greenness (SPAD), net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (E) in the leaf tissues of genotype KDML105 under Fe + Al toxicity significantly declined by 28.4%, 35.3%, 55.6%, and 51.6% over the control, respectively. In Azucena (AZU; Fe/Al tolerant), there was a rapid uptake of Fe and Al by OsYSL1 expression in the root tissues, but a limited secretion into vacuole organelles by OsVIT2, leading to a maintenance of low level of toxicity driven by an enhanced accumulation of glutathione together with downregulation of OsGR expression level. In addition, Fe and Al restrictions in the root tissues of genotype RD35 were evident; therefore, crop stress index (CSI) of Fe + Al-treated plants was the maximum, leading to an inhibition of gs (53.6% over the control) and E (49.0% over the control). Consequently, free proline, total phenolic compounds, and ascorbic acid in the leaf tissues of rice under Fe + Al toxicity significantly increased by 3.2, 1.2, and 1.5 folds over the control, respectively, indicating their functions in non-enzymatic antioxidant defense. Moreover, physiological parameters including leaf temperature (Tleaf) increment, high level of CSI (>0.6), SPAD reduction, photon yield of PSII (ΦPSII) diminution, Pn, gs, and E inhibition in rice genotype IR64 (Fe/Al-sensitive) under Fe + Al treatment were clearly demonstrated as good indicators of metal-induced toxicity. Our results on Fe- and/or Al-tolerant screening to find out the candidate genotypes will contribute to present screening and breeding efforts, which in turn help increase rice production in the Fe/Al-contaminated acid soil under lowland conditions.

Comparative proteomic analysis of Chlamydomonas reinhardtii control and a salinity-tolerant strain revealed a differential protein expression pattern.

MAIN CONCLUSION: Proteins involved in membrane transport and trafficking, stress and defense, iron uptake and metabolism, as well as proteolytic enzymes, were remarkably up-regulated in the salinity-tolerant strain of Chlamydomonas reinhardtii. Excessive concentration of NaCl in the environment can cause adverse effects on plants and microalgae. Successful adaptation of plants to long-term salinity stress requires complex cellular adjustments at different levels from molecular, biochemical and physiological processes. In this study, we developed a salinity-tolerant strain (ST) of the model unicellular green alga, Chlamydomonas reinhardtii, capable of growing in medium containing 300 mM NaCl. Comparative proteomic analyses were performed to assess differential protein expression pattern between the ST and the control progenitor cells. Proteins involved in membrane transport and trafficking, stress and defense, iron uptake and metabolism, as well as protein degradation, were remarkably up-regulated in the ST cells, suggesting the importance of these processes in acclimation mechanisms to salinity stress. Moreover, 2-DE-based proteomic also revealed putative salinity-specific post-translational modifications (PTMs) on several important housekeeping proteins. Discussions were made regarding the roles of these differentially expressed proteins and the putative PTMs in cellular adaptation to long-term salinity stress.