title: Salt-dependent increase in triterpenoids is reversible upon transfer to fresh water in mangrove plants Kandelia candel and Bruguiera gymnorrhiza.
abstract: This study examined the salinity dependence of triterpenoid content and triterpenoid synthase gene expression in mangrove plants, Kandelia candel and Bruguiera gymnorrhiza (Rhizophoraceae) after long-term exposure to salinity and subsequent re-adaptation. Seedlings of the two mangrove species grown in varying salt concentrations for 4 months were divided into two treatment groups and grown for another 4 months, one group continued under the respective saline condition and the other in fresh water for re-adaptation. The total content of triterpenoids increased with increasing salinity in roots and leaves of K. candel, but only in roots in B. gymnorrhiza. This increase was reversed to a variable extent, depending on the species and organ, after transfer to fresh water. In contrast, the total content of phytosterols showed no correlation with salinity throughout the experiment. The increase in total triterpenoids was accompanied by an up-regulation of several triterpenoid synthase genes: KcMS, a multifunctional triterpenoid synthase, in roots and leaves of K. candel and BgLUS, a lupeol synthase, and BgbAS, a β-amyrin synthase, in roots of B. gymnorrhiza. The expression of root KcCAS, a cycloartenol synthase, which is involved in phytosterol biosynthesis, was not modulated by the salinity conditions but decreased with increasing salinity in leaves, followed by the restoration to the initial level after transfer to fresh water. The concentrations of individual triterpenoids, but not of phytosterols, in the roots positively correlated with the salinity. These results reinforced the importance of triterpenoids in the adaptation of mangroves to withstand salt and/or water stress.
authors.affiliation: Tropical Biosphere Research Center, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Basyuni
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Baba
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kinjo
authors.forename: Lollie A P
authors.initials: LA
authors.lastname: Putri
authors.forename: Luthfi
authors.initials: L
authors.lastname: Hakim
authors.forename: Hirosuke
authors.initials: H
authors.lastname: Oku
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism; D009928:Organ Specificity; D010840:Phytosterols / Q000032:analysis / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D043982:Rhizophoraceae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D054712:Salinity; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology*; D013045:Species Specificity; D014315:Triterpenes / Q000032:analysis / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D010840:Phytosterols; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D014315:Triterpenes; D012965:Sodium Chloride; D019751:Intramolecular Transferases; C039924:2,3-oxidosqualene-beta-amyrin-cyclase; C117114:lupeol synthase