Research article

Comparison of transcripts in Phalaenopsis bellina and Phalaenopsis equestris (Orchidaceae) flowers to deduce monoterpene biosynthesis pathway

Yu-Yun Hsiao¹ , Wen-Chieh Tsai^1,7 , Chang-Sheng Kuoh¹ , Tian-Hsiang Huang² , Hei-Chia Wang² , Tian-Shung Wu³ , Yann-Lii Leu⁴ , Wen-Huei Chen⁵ and Hong-Hwa Chen^1,6

¹Department of Life Sciences, National Cheng-Kung University, Tainan 701, Taiwan

²Institue of Information Management, National Cheng Kung University, Tainan 701, Taiwan

³Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan

⁴Graduate Institute of Natural Products, Chang Gung University, Taoyuan 333, Taiwan

⁵Department of Life Sciences, National University of Kaohsiung, Kaohsiung 811, Taiwan

⁶Institute of Biotechnology, National Cheng Kung University, Tainan 701, Taiwan

⁷Department of Biological Science and Technology, Chung-Hwa College of Medical Technology, Tainan Hsien 717, Taiwan

author email corresponding author email

BMC Plant Biology 2006, 6:14doi:10.1186/1471-2229-6-14

Published:	13 July 2006

Abstract

Background

Floral scent is one of the important strategies for ensuring fertilization and for determining seed or fruit set. Research on plant scents has hampered mainly by the invisibility of this character, its dynamic nature, and complex mixtures of components that are present in very small quantities. Most progress in scent research, as in other areas of plant biology, has come from the use of molecular and biochemical techniques. Although volatile components have been identified in several orchid species, the biosynthetic pathways of orchid flower fragrance are far from understood. We investigated how flower fragrance was generated in certain Phalaenopsis orchids by determining the chemical components of the floral scent, identifying floral expressed-sequence-tags (ESTs), and deducing the pathways of floral scent biosynthesis in Phalaneopsis bellina by bioinformatics analysis.

Results

The main chemical components in the P. bellina flower were shown by gas chromatography-mass spectrometry to be monoterpenoids, benzenoids and phenylpropanoids. The set of floral scent producing enzymes in the biosynthetic pathway from glyceraldehyde-3-phosphate (G3P) to geraniol and linalool were recognized through data mining of the P. bellina floral EST database (dbEST). Transcripts preferentially expressed in P. bellina were distinguished by comparing the scent floral dbEST to that of a scentless species, P. equestris, and included those encoding lipoxygenase, epimerase, diacylglycerol kinase and geranyl diphosphate synthase. In addition, EST filtering results showed that transcripts encoding signal transduction and Myb transcription factors and methyltransferase, in addition to those for scent biosynthesis, were detected by in silico hybridization of the P. bellina unigene database against those of the scentless species, rice and Arabidopsis. Altogether, we pinpointed 66% of the biosynthetic steps from G3P to geraniol, linalool and their derivatives.

Conclusion

This systems biology program combined chemical analysis, genomics and bioinformatics to elucidate the scent biosynthesis pathway and identify the relevant genes. It integrates the forward and reverse genetic approaches to knowledge discovery by which researchers can study non-model plants.