The response of Hymenocrater longiflorus to water stress and proline application under in vitro cultivation

Abstract

Hymenocrater longiflorus Benth. (surahalala) is a wild plant species having properties to be categorized as both pharmaceutical and ornamental plants. To date, the genomics of this plant is unknown and the gene expression profiling of the genes related to its metabolite has never been studied before. In order to study the responses of surahalala plant grown under in vitro conditions to abiotic stresses and the deferential expressions of the genes related to its essential oils under exogenous proline application; three levels of PEG6000 (0, 10, and 20%) and five levels of proline (0, 5, 10, 15, and 20 µM) were applied in mixture with its culture medium. Accordingly, induced water deficit increased oxidant levels while decreased fresh weight of surahalala tissues; whereas, application of proline up to 15 µM was able to relatively compensate the negative effect of water deficit. Contrarily, high proline level (20 µM) showed negative effect surahalala plants which is probably due to the stress simulation (nutrition) in this plant under high proline concentration. Since PEG and proline applications increased essential oil contents, the best combination of proline and PEG treatment in the surahalala plant for achieving the highest content of its essential oils were 10 µM and 10% levels, respectively. The expression profiles of TPS27, L3H, TPS2, TPS1, OMT and GDH3 in this plant were successfully carried out and the results verified the involvement of these genes in 1,8-cineole, carvone, α-pinene, thymol, estragole, and β-Citronellol biosynthesis, respectively. In addition, our results indicated that these genes could get involved in the other metabolite synthesis under water deficit conditions.