Characterization and nitrogen deficiency response of ATP-citrate lyase from unicellular alga Dunaliella tertiolecta

ATP-citrate lyase (ACL) catalyzes the formation of cytosolic acetyl-CoA, which is responsible for the biosynthesis of fatty acids, lipids, and flavonoid. Here, cDNAs of the small and large subunits of ACL (DtACLA and DtACLB) and their genomic sequences were isolated from Dunaliella tertiolecta using RT-PCR, RACEs and genomic walking techniques. It was found that there were 12 exons and 11 introns in DtACLA, and 20 exons and 19 introns in DtACLB. PlantPAN and PlantCARE revealed a number of putative transcription factor binding sites in the 5′-flanking regions of DtACLA and DtACLB. Conserved domain analysis and phylogenetic analysis showed that ACLA and SCSβ may share the common evolutionary origin, and ACLB may have a common origin from the fusion and divergence of SCSα and CS. The recombinant DtACLA and DtACLB in E. coli BL21 (DE3) seemed to be expressed mainly in the form of insoluble fraction. The transcription levels of DtACLA and DtACLB were fairly consistent with lipid accumulation in response to nitrogen deficiency, suggesting that both subunits of ACL from D. tertiolecta may be coordinate to function in the catalysis, and their activity was related to the lipid accumulation in D. tertiolecta.