期刊
PLANT JOURNAL
卷 71, 期 2, 页码 205-215出版社
WILEY
DOI: 10.1111/j.1365-313X.2012.04972.x
关键词
Arabidopsis; chloroplast; hotdog-fold; peroxisome; phylloquinone; Synechocystis
资金
- National Science Foundation [MCB-0918258]
- Center for Plant Science Innovation
It is not known how plants cleave the thioester bond of 1,4-dihydroxy-2-naphthoyl-CoA (DHNA-CoA), a necessary step to form the naphthoquinone ring of phylloquinone (vitamin K1). In fact, only recently has the hydrolysis of DHNA-CoA been demonstrated to be enzyme driven in vivo, and the cognate thioesterase characterized in the cyanobacterium Synechocystis. With a few exceptions in certain prokaryotic (Sorangium and Opitutus) and eukaryotic (Cyanidium, Cyanidioschyzon and Paulinella) organisms, orthologs of DHNA-CoA thioesterase are missing outside of the cyanobacterial lineage. In this study, genomic approaches and functional complementation experiments identified two Arabidopsis genes encoding functional DHNA-CoA thioesterases. The deduced plant proteins display low percentages of identity with cyanobacterial DHNA-CoA thioesterases, and do not even share the same catalytic motif. GFP-fusion experiments demonstrated that the Arabidopsis proteins are targeted to peroxisomes, and subcellular fractionations of Arabidopsis leaves confirmed that DHNA-CoA thioesterase activity occurs in this organelle. In vitro assays with various aromatic and aliphatic acyl-CoA thioester substrates showed that the recombinant Arabidopsis enzymes preferentially hydrolyze DHNA-CoA. Cognate T-DNA knock-down lines display reduced DHNA-CoA thioesterase activity and phylloquinone content, establishing in vivo evidence that the Arabidopsis enzymes are involved in phylloquinone biosynthesis. Extraordinarily, structure-based phylogenies coupled to comparative genomics demonstrate that plant DHNA-CoA thioesterases originate from a horizontal gene transfer with a bacterial species of the Lactobacillales order.
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