Photosystem biogenesis in the thylakoid membrane is a highly complicated process that requires the coordinated assembly of nucleus-encoded and chloroplast-encoded protein subunits as well as the insertion of hundreds of cofactors, such as chromophores (chlorophylls, carotenoids) and iron-sulfur clusters. The molecular details of the assembly process and the identity and functions of the auxiliary factors involved in it are only poorly understood. In this work, we have characterized the chloroplast genome-encoded ycf4 (for hypothetical chloroplast reading frame no. 4) gene, previously shown to encode a protein involved in photosystem I (PSI) biogenesis in the unicellular green alga Chlamydomonas reinhardtii. Using stable transformation of the chloroplast genome, we have generated ycf4 knockout plants in the higher plant tobacco (Nicotiana tabacum). Although these mutants are severely affected in their photosynthetic performance, they are capable of photoautotrophic growth, demonstrating that, different from Chlamydomonas, the ycf4 gene product is not essential for photosynthesis. We further show that ycf4 knockout plants are specifically deficient in PSI accumulation. Unaltered expression of plastid-encoded PSI genes and biochemical analyses suggest a posttranslational action of the Ycf4 protein in the PSI assembly process. With increasing leaf age, the contents of Ycf4 and Y3IP1, another auxiliary factor involved in PSI assembly, decrease strongly, whereas PSI contents remain constant, suggesting that PSI is highly stable and that its biogenesis is restricted to young leaves.

A spacer peptide (Glu-Ala repeats) connects N-terminal of a polypeptide precursor to the signal peptide of α-mating factor (α-MF) from Saccharomyces cerevisiae. During the polypeptide precursor secretion, the signal peptide will be first cleaved by signal peptidase in the endoplasmic reticulum, followed by Kex2 endopeptidase and finally the spacer peptide is removed by dipeptidyl aminopeptidase in the Golgi apparatus. In the case of insulin precursor, unfortunately, mixture forms of the insulin precursor containing a spacer peptide and the correct insulin precursor is observed in Pichia pastoris. To overcome this problem, a gene encoding insulin Aspart precursor without the spacer peptide has been constructed and its expression has been investigated in this study. The gene of insulin Aspart precursor has been successfully expressed extracellularly in P. pastoris KM71 with molecular mass of 6306.8 Da as determined by LC-ESI-MS. The expression level of insulin Aspart precursor is affected by aeration, cell density and methanol as an inducer. In shake flask production, the insulin Aspart precursor was optimally produced by 3% methanol induction every 24 h for two days, at initial cell density (OD600) of 60 and aeration (ratio of culture volume to flask volume) of 1:25. Based on Western blot analysis, there is no intracellular insulin Aspart precursor detected. Therefore, the spacer peptide is not essential for insulin Aspart precursor secretion in P. pastoris and removal of spacer resulted in insulin Aspart precursor homogeneity.

Artemisinin, a secondary metabolite in Artemisia annua is one of primary choice for the treatment of malaria, it is naturally produced in low concentration from this plant. This study was aimed to clone key enzymes of artemisinin production in order to enhance its production through the semi-synthetically production in Saccharomyces cerevisiae. Methods: Two key enzymes in artemisinin biosynthetic pathway which are farnesyl phosphate synthase (fps) and amorpha-4,11-diene synthase (ads) genes were transformed into S. cerevisiae using pBEVY vector. Successful transformation was checked by polymerase chain reaction (PCR) method and sequencing analysis Results: Recombinant plasmids which are pBEVY-GU_ads and pBEVY_GL_fps were successfully constructed. The optimized ads gene was amplified using PCR with a couple of primers that are designed in order to provide the homolog recombination between ads gene with the expression plasmid of pBEVY-GU respectively. While the A. annua optimized fps gene was cloned using classical method. Transformants were grown in selective media Synthetic Defined (SD) without leucine for transformants contain plasmid pBEVY-GL_fps and media without uracil for transformants contain plasmid pBEVY-GU_ads. Confirmation of colonies was done by PCR with primers to amplify fps and ads. DNA from yeast was isolated from positive colonies then transformed to E. coli. Plasmid from E. coli was isolated for restriction analysis and sequencing. Protein expression was induced by cultivating the yeast in the media with 2% galactose. Conclusion: Based on PCR, restriction and sequencing analysis, it could be concluded that fps and ads genes were successfully constructed, transformed and expressed in S. cerevisiae.

Background: Immediate and accurate diagnosis of malaria is essential for effective control of this disease. Immunochromatographic based rapid diagnostic tests (RDTs)  are economical, simple to perform, and provide results in a relative short time, can be useful to assist effective management of malaria. The commercially available malaria RDT in Indonesia is still imported. Therefore, an effort to produce malaria RDT independently is necessary. One of the biomarkers used in RDTs is Plasmodium lactate dehydrogenase pLDH. The production and accumulation of pLDH during asexual stage or blood-stage in all human infected malaria parasites can be used to indicate parasites viability, which is correlated with the number of parasites present in the plasma of infected patients.  Objective: The aim of this research is to produce recombinant PfLDH in Escherichia coli BL21(DE3).Methods: PfLDH gene was cloned into pET30a expression vector to obtain a 6.2 kbp recombinant plasmid pET30a-PfLDH. E. coli BL21(DE3) was transformed with pET30a-PfLDH using the heat shock method. Then, E. coli BL21(DE3)- pET30a-PfLDH was cultured in LB broth containing 50 mg/mL kanamycin and was induced by 1mM IPTG at 37oC.Results: SDS-PAGE and Western Blot analysis showed that recombinant PfLDH was expressed with molecular mass ~30 kDa.Conclusion: Recombinant PfLDH is expressed in E. coli BL21(DE3) and can be used in further research for producing rPfLDH as a biomarker for malaria RDT development.