Cloning And Phylogenetic Analysis Of PDS Gene In Ulva Pertusa

Carotenoids as a natural pigment widely exist in Plant and bacterial. It reported thatsometimes carotenoids played an active role in the mechanism to adapt to high light. Howeverthe resources of carotenoids are quite limited, because it is mainly formed through thebiosynthesis and very difficult to obtain by chemical synthesis. Phytoene desaturase (PDS) isthe most important rate-limiting key enzyme in the pathway of carotenoid biosynthesis, and isalso the key enzyme to change carotenoid molecules from colorless to color. Theinvestigation on PDS will help us understand the mechanism of carotenoid biosynthesis. U.pertusa as common intertidal zone green algae is often eaten by the people as a healthy food.A study on the mechanism of carotenoid biosynthesis and the role of PDS in the biosyntheticpathway will reveal the reasons why U. pertusa is able to adapt the violent irradiation anddrastic osmotic stress. Therefore it might help to make deeper understanding to themechanism of the intertidal algae to adapt or tolerate to the harsh environment.In the study, U. pertusa were collected at coastal area of Fujiazhuang, Dalian. Thesuppression subtractive hybridization and3’-RACE PCR methods were employed to clonethe PDS3’-fragament. The DNA sequence length of PDS cloned is1263bp.By searching the NCBI database, the50amino acid sequences of50different plant PDSgenes were selected and the phylogenetic relationships between PDS genes including the genefragment we cloned were systemically analyzed. The analysis might provide some usefulinformation for the future function study of PDS genes. The results are as follows:(1)50PDS protein sequences of different species are found by searching and alignmentin NCBI database. Phytoene desaturase gene in bacterial was named CrtI and phytoenedesaturase gene in plant was named PDS.(2)The phylogenetic tree was constructed after multiple sequences alignment of the50protein sequences and the fragment we cloned. U. pertusa PDS was classified in green algaegroup and it had the closest relationship with Haematococcus pluvialis and Chlamydomonasreinhardtii. The phylogenetic tree was clearly classified the PDS and CrtI protein sequencesinto their respective categories. The result is accordance with the evolutionary rout of thespecies.(3)Using CDD online software, the conserved domains of50protein sequences wereanalyzed. All of the sequences contain a conserved NAD(P)-binding Rossmann-like domain.The length of CrtI conserved domain is32amino acid and that of plant conserved domain is51amino acid. (4)According to the results of alignment and species, we summarized the commonmodels of CrtI and PDS conserved domains.Analysis of the comparison results showed that there were some common patterns for themutation of amino acids among the species. Mutations of amino acid are consistent with theamino acids which exist in the same position of conserved domain in higher or lower plants.The founding implied there is a stable relationship among the species in the evolutionaryprocess.