Isolation and Analysis of the Cppsy Gene and Promoter from Chlorella protothecoides CS-41.

Phytoene synthase (PSY) catalyzes the condensation of two molecules of geranylgeranyl pyrophosphate to form phytoene, the first colorless carotene in the carotenoid biosynthesis pathway. So it is regarded as the crucial enzyme for carotenoid production, and has unsurprisingly been involved in genetic engineering studies of carotenoid production. In this study, the psy gene from Chlorella protothecoides CS-41, designated Cppsy, was cloned using rapid amplification of cDNA ends. The full-length DNA was 2488 bp, and the corresponding cDNA was 1143 bp, which encoded 380 amino acids. Computational analysis suggested that this protein belongs to the Isoprenoid_Biosyn_C1 superfamily. It contained the consensus sequence, including three predicted substrate-Mg(2+) binding sites. The Cppsy gene promoter was also cloned and characterized. Analysis revealed several candidate motifs for the promoter, which exhibited light- and methyl jasmonate (MeJA)-responsive characteristics, as well as some typical domains universally discovered in promoter sequences, such as the TATA-box and CAAT-box. Light- and MeJA treatment showed that the Cppsy expression level was significantly enhanced by light and MeJA. These results provide a basis for genetically modifying the carotenoid biosynthesis pathway in C. protothecoides.

Structure and function characterization of the phytoene desaturase related to the lutein biosynthesis in Chlorella protothecoides CS-41.

Phytoene desaturase is the key enzyme involved in the biosynthesis pathway of lutein. The unicellular microalga, Chlorella protothecoides CS-41, had been selected for the heterotrophic production of high concentrations of lutein. In this study, a cDNA copy of the pds gene from C. protothecoides was obtained using the rapid amplification of cDNA ends (RACE) technique. Phylogenetic analysis of the deduced amino acid sequence revealed that the phytoene desaturases derived from the algal family. Expression of the pds gene in Escherichia coli produced a single protein of 61 kDa. The PDS activity of the expressed protein was confirmed by the production of ζ-carotene as the result from the action of the enzyme's desaturation activity, which was identified by high-performance liquid chromatography and heterologous complementation analysis. Using random and site-directed mutagenesis, a single amino acid mutation (N144D) was identified and confirmed. This mutant encodes an inactive enzyme, which implies that amino acid 144 is crutial to the activity of the PDS enzyme. Therefore, by gene cloning and expression in prokaryotic cells, the gene for ζ-carotene production or as part of the biosynthetic pathway of lutein had been characterized from Chlorella protothecoides CS-41.

Cloning and characterization of the ζ-carotene desaturase gene from Chlorella protothecoides CS-41.

To elucidate the lutein biosynthesis pathway in the lutein-producing alga, Chlorella protothecoides CS-41, the ζ-carotene desaturase gene (zds) was isolated from Chlorella protothecoides using the approach of rapid amplification of cDNA ends. The full-length cDNA sequence was 2031 bp and contained 1755 bp putative open reading frame which encodes a 584 amino acid deduced polypeptide whose computed molecular weight was 63.7 kDa. Sequence homology research indicated that the nucleotide and putative protein had sequence identities of 72.5% and 69.5% with those of the green alga Chlamydomonas reinhardtii, respectively. Phylogenetic analysis demonstrated that the ZDS from C. protothecoides CS-41 had a closer relationship with those of chlorophyta and higher plants than with those of other species. In addition, we also found that the zds gene expression was upregulated in response to light.

Hot embossing of electrophoresis microchannels in PMMA substrates using electric heating wires.

A simple method based on electric heating wires has been developed for the rapid fabrication of poly(methyl methacrylate) (PMMA) electrophoresis microchips in ordinary laboratories without the need for microfabrication facilities. A piece of stretched electric heating wire placed across the length of a PMMA plate along its midline was sandwiched between two microscope slides under pressure. Subsequently, alternating current was allowed to pass through the wire to generate heat to emboss a separation microchannel on the PMMA separation channel plate at room temperature. The injection channel was fabricated using the same procedure on a PMMA sheet that was perpendicular to the separation channel. The complete microchip was obtained by bonding the separation channel plate to the injection channel sheet, sealing the channels inside. The electric heating wires used in this work not only generated heat; they also served as templates for embossing the microchannels. The prepared microfluidic microchips have been successfully employed in the electrophoresis separation and detection of ions in connection with contactless conductivity detection.

[Cloning and analysis of the gene encoding lycopene epsilon cyclase in Chlorella protothecoides CS-41].

OBJECTIVE: Lycopene epsilon cyclase (LCYE) is the key enzyme in the lutein synthesis pathway and catalyses linear lycopene to form cyclic epsilon-carotene, a presucursor of lutein. We aimed to clone the full-length cDNA of LCYE gene from Chlorella protothecoides CS-41, to predict the functional sites and the three-dimensional structure of LCYE through bioinformatics analysis and to confirm its activities and functions. METHOD: We used RACE (rapid-amplification of cDNA ends) essay and RT-PCR for the cloning of the full-length cDNA of LCYE from C. protothecoides CS-41. The online software such as PredictProtein, Pfam HMMs and Swiss-Model were used in bioinformatics analysis of the amino acid sequence of LCYE protein. We constructed the expression vector for LCYE gene with pET-28a(+) and transformed into Escherichia coli BL21 (DE3). Furthermore, the E. coli strain containing the pAC-LYC plasmid which could accumulate lycopene was used for the functional confirmation of LCYE from C. protothecoides CS-41. RESULTS: A 2107 bp cDNA (GenBank Accession No. FJ752528) sequence was cloned with 1731 bp open reading frame, encoding a putative LCYE, from C. protothecoides CS-41. Homology studies showed that the deduced amino acid sequence of LCYE gene had a significant similarity with the corresponding sequences of other green algae and higher plants. It shared the highest sequence identity, up to 67%, with the LCYE gene from Chlamydomonas reinhardtii. One typical lycopene cyclase protein domain (Pfam05834) was predicted between the 48th-459th amino acid. In addition, the sequence between 261th -284th was one typical conserved lycopene cyclase protein motif. The SDS-PAGE result showed that the LCYE gene was overexpressed in Escherichia coli BL21 (DE3) after the addition of IPTG. The prokaryotically expressed LCYE protein was able to transfer the color of the E. coli strain containing the pAC-LYC plasmid from pink to yellow. CONCLUSION: The full-length cDNA sequence of LCYE gene was successfully cloned with the size of 2107 bp. Several typical motifs were found and the three-dimensional structure of LCYE was constructed from Bioinformatics analysis. The generated phylogenetic tree showed the closest relationship between C. protothecoides CS-41 and C. reinhardtii among the listed organisms. Finally, the expression product of the LCYE gene cloned in the study was confirmed to hold the function and activity of lycopene epsilon cyclase.