Tài liệu Báo cáo khoa học: Fatty acid desaturases from the microalga Thalassiosira pseudonana pptx

Fatty acid desaturases from the microalga Thalassiosira

pseudonana

Thierry Tonon1,*, Olga Sayanova2

, Louise V. Michaelson2

, Renwei Qing1,†, David Harvey1

,

Tony R. Larson1

, Yi Li1

, Johnathan A. Napier2 and Ian A. Graham1

1 CNAP, Department of Biology, University of York, Heslington, York, UK

2 Rothamsted Research Institute, Harpenden, UK

The algae, as a group, represent the third largest aqua￾culture crop (after freshwater fish and molluscs) in the

world today [1,2]. In recent years, considerable atten￾tion has been directed at marine microalgae for the

production of oils and fatty acids, in particular the use

of algal oils containing long chain polyunsaturated

fatty acids (LCPUFAs). The most prominent of these

are the health beneficial omega-3 eicosapentaenoic acid

(EPA, 20:5D5,8,11,14,17) and docosahexaenoic acid

(DHA, 22:6D4,7,10,13,16,19). Among the alga groups iden￾tified as producers of high levels of LCPUFAs, di￾atoms are able to produce and accumulate EPA and

DHA in triacylglycerols (TAGs) [3]. For biotechno￾logical applications, these organisms are regarded as

Keywords

desaturases; long chain polyunsaturated

fatty acids; sphingolipids; Thalassiosira

pseudonana; yeast expression

Correspondence

I. A. Graham, Department of Biology

(area 7), University of York, PO Box373, UK

Fax: +44 1904 328762

Tel: +44 1904 328750

E-mail: [email protected]

Present addresses

*UMR 7139, CNRS-GOEMAR-UPMC,

Station Biologique, BP 74, 29682 Roscoff

cedex, France

College of Life Science, Sichuan University,

Chengdu, China

Note

The sequences reported in this paper have

been submitted to GenBank database under

the accession number AY817152 (TpdesO),

AY817153 (TpdesA), AY817154 (TpdesB),

AY817155 (TpdesI) and AY817156 (TpdesK)

(Received 13 March 2005, revised 22 April

2005, accepted 9 May 2005)

doi:10.1111/j.1742-4658.2005.04755.x

Analysis of a draft nuclear genome sequence of the diatom Thalassiosira

pseudonana revealed the presence of 11 open reading frames showing

significant similarity to functionally characterized fatty acid front-end

desaturases. The corresponding genes occupy discrete chromosomal loca￾tions as determined by comparison with the recently published genome

sequence. Phylogenetic analysis showed that two of the T. pseudonana

desaturase (Tpdes) sequences grouped with proteobacterial desaturases that

lack a fused cytochrome b5 domain. Among the nine remaining gene

sequences, temporal expression analysis revealed that seven were expressed

in T. pseudonana cells. One of these, TpdesN, was previously characterized

as encoding a D11-desaturase active on palmitic acid. From the six remain￾ing putative desaturase genes, we report here that three, TpdesI, TpdesO

and TpdesK, respectively encode D6

-, D5

- and D4

-desaturases involved

in production of the health beneficial polyunsaturated fatty acid DHA

(docosahexaenoic acid). Furthermore, we show that one of the remaining

genes, TpdesB, encodes a D8

-sphingolipid desaturase with strong preference

for dihydroxylated substrates.

Abbreviations

ARA, arachidonic acid; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; EST, expressed sequence tag; FAME, fatty acid methyl

ester; gDNA, genomic DNA; LCB, long chain base; LCPUFA, long chain polyunsaturated fatty acid; PUFAs, polyunsaturated fatty acids;

RACE, rapid amplification of cDNA ends; TAG, triacyglycerol; Tpdes, Thalassiosira pseudonana desaturase.

FEBS Journal 272 (2005) 3401–3412 ª 2005 FEBS 3401