Structural elucidation of selenocysteine insertion machinery of microalgal selenoprotein T and its transcriptional analysis.

Essential trace element selenium in association with selenoproteins, which is found in almost all organisms except higher plants and fungi, is involved in various biological functions. Advancement in the field of whole genome sequencing and data analyzing bioinformatic tools led to the accumulation of genome information of organisms. However, selenoproteins are unique and it needs specialized genomics tool for its identification as well as characterization. In this study, the presence of selenoprotein T (SelT) from Scenedesmus quadricauda was shown for the first time with experimental evidence and compared with SelT of marine microalgae Nannochloropsis oceanica. Along with SelT, all the associated machineries required to synthesize the selenoproteins were also identified. Also, the present study tried to explicate the evolutionary relatedness of SelT of these two organisms with other known bacteria and eukaryotes. Transcript level analysis in S. quadricauda under endoplasmic reticulum stress showed a 1.2 ± 0.28-fold increase in SelT expression. Thus, it provided the first experimental evidence on SelT expression from microalgae.

Selective degradation of the recalcitrant cell wall of Scenedesmus quadricauda CASA CC202.

MAIN CONCLUSION: An eco-friendly cell wall digestion strategy was developed to enhance the availability of nutritionally important bio molecules of edible microalgae and exploit them for cloning, transformation, and expression of therapeutic proteins. Microalgae are the source for many nutritionally important bioactive compounds and potential drugs. Even though edible microalgae are rich in nutraceutical, bioavailability of all these molecules is very less due to their rigid recalcitrant cell wall. For example, the cell wall of Scenedesmus quadricauda CASA CC202 is made up of three layers comprising of rigid outer pectin and inner cellulosic layer separated by a thin middle layer. In the present investigation, a comprehensive method has been developed for the selective degradation of S. quadricauda CASA CC202 cell wall, by employing both mechanical and enzymatic treatments. The efficiency of cell wall removal was evaluated by measuring total reducing sugar (TRS), tannic acid-ferric chloride staining, calcoflour white staining, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analysis. It was confirmed that the yield of TRS increased from 129.82 mg/g in 14 h from pectinase treatment alone to 352.44 mg/g by combined sonication and enzymatic treatment within 12 h. As a result, the combination method was found to be effective for the selective degradation of S. quadricauda CASA CC202 cell wall. This study will form a base for our future works, where this will help to enhance the digestibility and availability of nutraceutically important proteins.