Identification of gene isoforms and their switching events between male and female embryos of the parthenogenetic crustacean Daphnia magna

Kato Y., Nitta J.H., Perez C.A.G., et al. Identification of gene isoforms and their switching events between male and female embryos of the parthenogenetic crustacean Daphnia magna. Scientific Reports 14, 9407 (2024); https://doi.org/10.1038/s41598-024-59774-1.The cladoceran crustacean Daphnia exhibits phenotypic plasticity, a phenomenon that leads to diverse phenotypes from one genome. Alternative usage of gene isoforms has been considered a key gene regulation mechanism for controlling different phenotypes. However, to understand the phenotypic plasticity of Daphnia, gene isoforms have not been comprehensively analyzed. Here we identified 25,654 transcripts derived from the 9710 genes expressed during environmental sex determination of Daphnia magna using the long-read RNA-Seq with PacBio Iso-Seq. We found that 14,924 transcripts were previously unidentified and 5713 genes produced two or more isoforms. By a combination of Illumina short-read RNA-Seq, we detected 824 genes that implemented switching of the highest expressed isoform between females and males. Among the 824 genes, we found isoform switching of an ortholog of CREB-regulated transcription coactivator, a major regulator of carbohydrate metabolism in animals, and a correlation of this switching event with the sexually dimorphic expression of carbohydrate metabolic genes. These results suggest that a comprehensive catalog of isoforms may lead to understanding the molecular basis for environmental sex determination of Daphnia. We also infer the applicability of the full-length isoform analyses to the elucidation of phenotypic plasticity in Daphnia

Phycocyanin extraction in Spirulina produced using agricultural waste

Phycocyanin is a pigment-protein complex synthesized by blue-green microalgae such as Arthrospira (Spirulina) platensis. This pigment is used mainly as natural colouring in food industry. Previous studies have demonstrated the potential health benefits of this natural pigment. The price of phycocyanin is a vital factor that dictates its marketability. The cost of culturing the algae, particularly from the substrate used for growth, is one of the main factors that determine the price of phycocyanin. Another important factor is the growth yield of the algae. In our research, agricultural waste such as charcoal produced from rice husk was utilized for the algae cultivation to replace the synthetic chemicals such as urea and triple superphosphate used the mineral medium. The use of this low cost substrate increases the cell concentration by 60 % during 8 days cultivation to reach 0.39 g/l. The phycocyanin extraction was performed using water at the different biomass-to-solvent ratio and shaking rates. The phycocyanin concentration and purity (A615/A280) obtained were 1.2 g/l and 0.3. These values are 40 % and 20 % lower than the value obtained from the algae produced using the synthetic chemicals. Further purification produced the extract purity required for food grade. The biomass-solvent ratio does not significantly affect the extract purity; however the higher shaking rate during extraction reduces the purity. This finding demonstrates the potential of using rice husk as an alternative substrate to cultivate algae for phycocyanin extraction. Keywords:phycocyanin; Spirulina, Arthrospira platensis; agricultural waste; extraction

Utilization of n-Hexane as Co-solvent to Increase Biodiesel Yield on Direct Transesterification Reaction from Marine Microalgae

AbstractDirect transesterification reaction requires optimization of reaction conditions due to both the lipid extraction and lipid transesterification reactions that occur at the same place and time. Co-solvent utilization is considered as one of some ways to improve the yield in the direct transesterification reaction. In this study, transesterification was done directly on the marine microalgae biomass Nannochloropsis sp. Design variations in this research including the volume ratio of methanol: n-hexane, the molar ratio of lipid: methanol, and reaction time. From these variations, the volume ratio of methanol: n-hexane 1:1, molar ratio of lipid:methanol 1:400, and reaction time 4hours can increase biodiesel yield until 90.9% for Nannochloropsis sp. FAME contents were analyzed by Gas Chromatography and Mass Spectroscopy (GCMS). Saturated fatty acid content is more dominant on biodiesel reached 52.72%