Ethephon treatment reduced Mondo grass (Ophiopogon japonicus) gas exchange rate and gene expression of Rbcs

Background - Mondo grass (Ophiopogon japonicus) is a very important ornamental species and traditional Chinese herbal medicine. Genomic information of this plant is very limited. Ethephon (2-chloroethyl phosphonic acid, an ethylene-releasing compound) is a plant growth regulator with various systemic properties. The effect of ethephon on Mondo grass photosynthesis is unclear. Objectives - The study was carried out to evaluate if foliar ethephon application could promote photosynthesis rate of Mondo grass. Methods - Net photosynthesis rate (P-n) and stomatal conductance (g(s)) of Mondo grass was measured at various time points after ethephon treatment. In addition, a full-length enriched complementary DNA (cDNA) library from ethephon (0.5 g L-1) treated Mondo grass leaves was constructed to explore the underlying gene expression profile. Results - Ethephon treatment (ranging from 0.2 g L-1 to 1.5 g L-1) reduced Mondo grass P-n. Real time quantitative PCR results implied that ethephon inhibited Mondo grass leaf photosynthesis through down-regulating gene expression of Rubisco small subunit (Rbcs). Conclusion - Application of ethephon will not be an effective way in promoting P-n of Mondo grass. Moreover, our data provide the first extensive set of full-length cDNA sequence resources for Mondo grass and these resources will be useful for important genes discovery, functional analysis and understanding various molecular mechanisms for Mondo grass.