Changes in the Plant β-Sitosterol/Stigmasterol Ratio Caused by the Plant Parasitic Nematode <i>Meloidogyne incognita</i>

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 <i>Meloidogyne incognita,</i> are devastating pathogens known to circumvent plant defense mechanisms. In this study, we investigated the changes in sterols of agricultural important crops, <i>Brassica juncea</i> (brown mustard), <i>Cucumis sativus</i> (cucumber), <i>Glycine max</i> (soybean), <i>Solanum lycopersicum</i> (tomato) and <i>Zea mays</i> (corn), 21 days post inoculation (dpi) with <i>M. incognita</i>. The main changes affected the β-sitosterol/stigmasterol ratio, with an increase of β-sitosterol and a decrease of stigmasterol in <i>S. lycopersicum</i>, <i>G. max</i>, <i>C. sativus</i> and <i>Z. mays</i>. 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 <i>CYP710A11</i>, responsible for the conversion of β-sitosterol to stigmasterol. Our results showed that the expression of <i>CYP710A11</i> was in line with the sterol profile of tomato after <i>M. incognita</i> infection. Since sterols play a key role in plant-pathogen interactions, this finding opens novel insights in plant nematode interactions.