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Asian Journal of Agriculture and Development (AJAD) - Call for papers!

Characterization of Green Algae Dunaliella sp. and Cyanobacterial Isolate and Detection of the DXS Gene Encoding the Key Enzyme in Carotenoid Biosynthesis

(Indonesia), Doctor of Philosophy in Microbial Genetics (Gadjah Mada University)

Dissertation Abstract:

 

Carotenoid is known to synthesize through the well-known mevalonate (MVA) pathway. Recently, a non-mevalonate pathway (non-MVA) was discovered in green algae. The limiting step for carotenoid biosynthesis in the non-MVA/DOXP/MEP pathway was catalyzed by 1-Deoxy-D-xylulose-5-phosphate synthase enzyme, encoded by the DXS gene.

The study aimed to characterize two local isolates of a green algal species from Jepara (Dunaliella sp. and a cyanobacterial isolate) and to elucidate the possible carotenoid synthesis pathway employed in the two isolates. Morphological, ecophysiological, and molecular characterization had been conducted on two local isolates. Elucidation of the pathway was carried out by analyzing the presence of DXS gene on the two isolates, as it had been widely understood that DXS gene is the key and limiting enzyme in the non-MVA pathway. Detection of the DXS gene was conducted by polymerase chain reaction (PCR) amplification of the gene of interest using Escherichia coli, plants, and Synechocystis gene amplification primers. The mevalonate inhibitor lovastatin and hybridization methods were carried out to reaffirm PCR result.

Morphological, ecophysiological, and molecular characterization demonstrated that cyanobacterial isolate was a prokaryotic algae, while Dunaliella sp. was eukaryotic algae. Cyanobacterial isolate demonstrated striking homology with Cyanobacterium MBIC 1210 and Synechocystis. Dunaliella sp., on the other hand, was a species of D. salina showing 99 percent homologies. Detection of the DXS gene in the two isolates showed about 9-50 percent homology with the known DXS gene. Low homology with the current DNA amplification approach supported with biochemical experiment using lovastatin and hybridization resulted in suggesting that the DXS gene was absent in the two isolates.