Differential tissue distribution of defense compounds in Jacobaea vulgaris, Jacobaea aquatica and their crosses

Differential tissue distribution of defense compounds in Jacobaea vulgaris, Jacobaea aquatica and their crosses.

 

Tri Rini Nuringtyas^1,2 Young Hae Choi¹, Kirsten Leiss³, P.G.L. Klinkhamers³, Rob Verpoorte¹

¹ Division Pharmacognosy, Section Metabolomics, Institute of Biology, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands

² Faculty of Biology, Gadjah Mada University, Indonesia

³ Plant Ecology and Phytochemistry Department, Institute of Biology, Leiden University, Sylvisusweg 72, 2333 BE Leiden,The Netherlands

The epidermis protects the inner-cell leaf from the external environment.  Therefore, metabolome in the epidermis is important as the first barrier against abiotic and biotic factors. In this study we investigated the epidermis metabolome of Jacobaea vulgaris, Jacobaea aquatica and their hybrids. For isolation of epidermis extracts, carborundum abrasion (CA) technique was applied. Subsequently, ¹H nuclear magnetic resonance (NMR) spectroscopy and multivariate data analyses were applied to compare the metabolome of the epidermal extracts with the abraded (mesophyll) extracts. Orthogonal partial least-squares-discriminant analysis (OPLS-DA) of the processed ¹H NMR showed a clear separation among the two different tissue extracts. The epidermal extracts contained significantly higher amounts of phenylpropanoids which were four times as much 5-O-caffeoyl quinic acid (CQA) and one and a half times as much 3-O-CQA  and feruloyl quinic acid (FQA) compared to the mesophyll extracts. Both CQA and FQA are known for their inhibitory effect on herbivores and pathogens.  Also the defence compounds jacobine-type pyrrolizidine alkaloids (PAs) were identified. They were slightly increased in the mesophyll. Comparison of the epidermal extracts revealed a clear discrimination between parental species and hybrids. J. vulgaris contained higher amounts of proline, succinic acid and jacobine-like PAs while J. aquatica contained higher amount of sucrose, fructose, and the PA senecionine. The hybrids metabolome contained compounds of both parents in intermediate amounts and no new compounds were detected. Our results emphasize the importance of studying the appropriate leaf tissue for chemical defences of herbivores and pathogens.

Keywords: Jacobaea sp, defence compounds, tissue distribution, metabolomics, NMR