Abstract
Sterols play a key role in various physiological processes of plants. Commonly, stigmasterol, β-sitosterol and campesterol represent the main plant sterols, and cholesterol is often reported as a trace sterol. Changes in plant sterols, especially in β-sitosterol/stigmasterol levels, can be induced by different biotic and abiotic factors. Plant parasitic nematodes, such as the root-knot nematode Meloidogyne incognita, are devastating pathogens known to circumvent plant defense mechanisms. In this study, we investigated the changes in sterols of agricultural important crops, Brassica juncea (brown mustard), Cucumis sativus (cucumber), Glycine max (soybean), Solanum lycopersicum (tomato) and Zea mays (corn), 21 days post inoculation (dpi) with M. incognita. The main changes affected the β-sitosterol/stigmasterol ratio, with an increase of β-sitosterol and a decrease of stigmasterol in S. lycopersicum, G. max, C. sativus and Z. mays. Furthermore, cholesterol levels increased in tomato, cucumber and corn, while cholesterol levels often were below the detection limit in the respective uninfected plants. To better understand the changes in the β-sitosterol/stigmasterol ratio, gene expression analysis was conducted in tomato cv. Moneymaker for the sterol 22C-desaturase gene CYP710A11, responsible for the conversion of β-sitosterol to stigmasterol. Our results showed that the expression of CYP710A11 was in line with the sterol profile of tomato after M. incognita infection. Since sterols play a key role in plant-pathogen interactions, this finding opens novel insights in plant nematode interactions.
Highlights
Plants are consistently exposed to numerous pests and pathogens, which leads to variations in plant metabolism, including sterol profiles
With 80.7% stigmasterol in corn root systems, our data are in agreement with previous reports of Bladocha and Benveniste [24], which showed that sterol composition of corn roots and leaves differed strongly in the ratio of β-sitosterol to stigmasterol
In the medicinal plant Cannabis, significant differences in campesterol, β-sitosterol and stigmasterol have been observed between organs, with βsitosterol as the most abundant sterol in stem bark and roots and stigmasterol being most abundant in leaves
Summary
Plants are consistently exposed to numerous pests and pathogens, which leads to variations in plant metabolism, including sterol profiles. Sterols are biomolecules which play important roles in various biological processes. Besides their essential function in cell membrane support and fluidity, they are important as hormone precursors and are involved in biotic and abiotic stress responses [1,2,3,4,5]. Sterols belong to the large group of isoprenoid synthesized via the lanosterol (animals and fungi) or cycloartenol (plants) pathway (Figure 1), sharing a basic structure with a four-cyclic hydrocarbon ring, called gonane, and a hydroxyl group at position C-3. Sterols are differently modified in the ring structure or in the side chain at position C-17, by methylations or double bonds [4,6]. Plants largely contain a mixture of C-24 sterols, such as β-sitosterol, campesterol and stigmasterol (collectively known as phytosterols)
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