Metabolizam nepetalaktona u listovima odabranih vrsta roda Nepeta (Lamiaceae) i njegova regulacija tokom dehidratacije
Metabolism of nepetalactone in leaves of selected species of the genus Nepeta (Lamiaceae) and its regulation during dehydration
Doctoral thesis (Published version)
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The specialized metabolism of the genus Nepeta (Lamiaceae) is distinguished by the monoterpenoid iridoid nepetalactone (NL), which exists in the form of 4 diastereoisomers with a 7S configuration. Although its biological activities are well-studied, the NL metabolism, as well as its role in plants, is not well understood. Results of this doctoral thesis describe the regulatory mechanisms determining NL biosynthesis during dehydration, in leaves of Nepeta rtanjensis Diklić & Milojević and N. argolica Bory & Chaub subsp. argolica, which are adapted to xerothermic habitats. Despite a coordinated decrease in the expression of 10 candidate iridoid-related biosynthetic genes and reduced metabolic activity, these species have developed mechanisms to preserve NL levels under water deficit conditions. These mechanisms include the significant role of MYC2 and YABBY5 transcription factors as positive regulators of NL biosynthesis, reduced intensity of NL catabolism, and preservation of the morphology of glandular trichomes – the major site of NL biosynthesis and accumulation. Iridoid synthases, functionaly characterized by in vitro enzymatic assays using recombinant proteins heterologously expressed in Escherichia coli, are expressed in NL-producing N. rtanjensis (NrIS2) and N. sibirica L. (NsIS), as well as in N. nervosa L. (NnIS), which is characterized by the absence of NL in tissues. N. nervosa probably possesses inactive iridoid biosynthetic platform, most likely due to the "switching off" or "silencing" of some genes upstream in the pathway. Elucidation of the regulatory mechanisms behind NL metabolism in Nepeta, provides the background for future metabolic engineering of NL production, and highlightes N. nervosa as an interesting model species for future studies.
Keywords:cis; Trans-nepetalactol; Dehydration; Functional characterization of genes; Iridoid synthase; Nepeta; Nepetalactone; Polyethylene glycol; Transcription factors
Source:Faculty of Biology, University of Belgrade, 2020, 1-147
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