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Title: Molecular cloning and expression profile of ß-ketoacyl-acp synthase gene from tung tree (Vernicia fordii Hemsl.)

Author
item LONG, HONGXU - Central South University Of Forestry And Technology
item TAN, XIAOFENG - Central South University Of Forestry And Technology
item YAN, FANGFANG - Central South University Of Forestry And Technology
item ZHANG, LIN - Central South University Of Forestry And Technology
item LI, ZE - Central South University Of Forestry And Technology
item Cao, Heping

Submitted to: Genetika
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2014
Publication Date: 4/30/2015
Citation: Long, H., Tan, X., Yan, F., Zhang, L., Li, Z., Cao, H. 2015. Molecular cloning and expression profile of ß-ketoacyl-acp synthase gene from tung tree (Vernicia fordii Hemsl.). Genetika. 47(1):143-159.

Interpretive Summary: Tung tree (Vernicia fordii) is an economically important non-edible woody oil tree originated in China. It is mainly distributed in subtropical areas of China, Argentina, Paraguay, Africa and southeastern region of the United States. It has been grown in China for the production of tung oil for centuries. Tung tree seeds contain 50-60% oil with about 80 mole a-eleostearic acid. Because of the three special conjugated double bonds in eleostearic acid, tung oil is easily oxidized and forms a unique polymer after being exposed to air, to form a tough, glossy, waterproof, insulative and anticorrosion surface on the object it is coating. Tung oil is widely used in paints, varnishes, coatings and finishes due to these excellent properties. Biosynthesis of fatty acids such as a-eleostearic acid in tung tree is catalyzed by the concerted action of acetyl-CoA carboxylase and fatty acid synthase, a multienzyme complex including ß-ketoacyl-acyl-carrier-protein synthase (KAS). Little is known about KAS in tung tree. The objective of this study was to clone KAS genes and analyze their expression profiles in tung tree. We report the cloning and expression of two cDNAs isolated from V. fordii, designated VfKAS II (partial sequence) and VfKAS III (full-length sequence), which encodes putative ß-ketoacyl ACP synthases likely involved in carbon-chain elongation. Sequence analysis showed that the full-length VfKAS III shared close identity with KAS III of other plants. QPCR analysis indicated that VfKAS III was expressed in all tissues examined. These molecular analyses of VfKAS III provided insights into the regulation of fatty acid biosynthesis and would help to improve oil content of V. fordii through the development of transgenic plants.

Technical Abstract: Tung tree (Vernicia fordii) is an important woody oil tree. Tung tree seeds contain 50-60% oil with approximately 80 mole a-eleostearic acid (9cis, 11trans, 13trans octadecatrienoic acid). Fatty acid synthesis is catalyzed by the concerted action of acetyl-CoA carboxylase and fatty acid synthase, a multienzyme complex including ß-ketoacyl-acyl-carrier-protein synthase (KAS). Little is known about KAS in tung tree. The objective of this study was to clone KAS genes and analyze their expression profiles in tung tree. A full-length cDNA encoding KAS III and a partial cDNA encoding KAS II were isolated from tung tree by PCR cloning using degenerate primers and rapid amplification of cDNA ends system. The full-length cDNA of VfKAS III was 1881 bp in length with an open reading frame of 1212 bp. VfKAS III genomic DNA was also isolated and sequenced, which contained 8 exons in 5403 bp length. The deduced VfKAS III protein shared approximately 80% identity with homologous KAS IIIs from other plants. Quantitative PCR analysis revealed that KAS II and KAS III were expressed in all of the tissues and organs tested but exhibited different expression patterns in tung tree. The expression levels of KAS II in young tissues were much lower than those in mature tissues, whereas the highest expression levels of KAS III were observed in young stem and young leaf. These results should facilitate further studies on the regulation of tung oil biosynthesis by KAS in tung tree.