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Title: Characterization of a lipoate-protein ligase A gene of rice (Oryza sativa L.)

Author
item KANG, SANG GIU - YEUNGNAM UNIVESITY, KOREA
item JEONG, HEY KYEONG - YEUNGNAM UNIVERSITY,KOREA
item LEE, EUN KYUNG - YEUNGNAM UNIVERSITY,KOREA
item Natarajan, Savithiry - Savi

Submitted to: Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2007
Publication Date: 1/18/2007
Citation: Kang, S., Jeong, H., Lee, E., Natarajan, S.S. 2007. Characterization of a lipoate-protein ligase A gene of rice (Oryza sativa L.). Gene. 393(1):53-61.

Interpretive Summary: In plants, lipoic acid is an essential compound (cofactor) required for the proper function of key metabolic pathways. Although lipoic acid attachment to some proteins is critically important for their proper cellular function, little is known about how plant cells make lipoic acid and how the lipoic acid becomes attached to specific proteins. In this study, we demonstrated that a rice gene, OsLPLA, is involved in attaching lipoic acid to lipoate-dependent enzymes. Our research provides essential information about the OsLPLA gene in rice, a first step toward understanding a key metabolic pathway for energy production in plants. Our findings will be useful to scientists working to increase tolerance to various stresses and to improve crop yield.

Technical Abstract: Lipoic acid (1,2-dithiolane-3-pentanoic acid) is an essential disulfide cofactor required for lipoate-dependent enzymes such as pyruvate dehydrogenase, ' -ketoglutarate dehydrogenase, and glycine cleavage enzyme complexes which function in key metabolic pathways in most prokaryotes and eukaryotes. Lipoic acid is covalently bounds to the lipoate-dependent enzymes by lipoate-protein ligase or lipoate transferase. Although lipoate-protein ligase is critical enzyme to complete the citric acid cycle, no functional lipoate-protein ligase gene of plants has been reported. We have identified and characterized a putative lipoyl-protein ligase A (OsLPLA) gene of rice. The OsLPLA gene consists of six exons on chromosome 8 of the physical map of Oryza sativa cv. Japonica. The OsLPLA gene encodes 270 amino acids, which show a weak homology to a lipoate-protein ligase A of E. coli. The OsLPLA transcripts were expressed abundantly in leaves and developing seeds undertaking active cell metabolism. In the genetic complementation analysis, the OsLPLA gene substituted functionally to lipoate-protein ligase A in a lplA null E. coli mutant. The OsLPLA protein transferred lipoate molecules to lipoate-dependent enzymes, including E2 subunits of the pyruvate dehydrogenase, E2o subunit of the '-ketoglutarate dehydrogenase and H-protein of the glycine decarboxylase in E. coli. Based on these results, we confirmed that the rice OsLPLA gene encodes a protein capable of catalyzing a covalent attachment of lipoate onto lipoate-dependent enzymes for essential metabolism.