Investigation of Differential Genes Expression in the Genome of Epipactis flava Seidenf. (Orchidaceae) under Flooded Condition Using cDNA-SRAP Analysis

Epipactis flava Seidenf. is classified into a rare type of orchid species, a rheophyte. The specific habitat for its life cycle requires a strong current and flooding time. In this study, differential gene expression between submerged and non-submerged conditions was studied using the cDNA-SRAP method. RNAs were extracted from rhizomes at 0, 6, 12, 24 and 48 hours after submergence. Seven candidate genes were selected to study the relative gene expression by real-time RT-PCR and found to be upregulated in submergence condition. Six of these, RNA polymerase sigma factor gene, ATPase gene, Plant homeodomain finger Alfin-like genes, DNA-3-methyladenine glycosylase gene, and Allene oxide synthase gene were induced to the highest level within 12 hrs. Subsequently, the expression of five genes decreased at 24 and 48 hrs of treatment except for UDP-glucosyl transferase gene which showed stable expression at all time. Apart from others, dolichyl-diphosphooligosaccharide glycosyl transferase gene was induced to the highest level at 24 hrs and was stable until 48 hrs. This suggested that the induction of genes expression by flooding occurred within 12-24 hrs and most genes in this finding involved in stress responses which were easily upregulated in rheophytic plants during submergence. The more differentially expressed genes should be analysed for a further understanding of the rheophytic habit of this plant.