Tomato Sterol 22-desaturase Gene : Its Roles in Infection and Plant Stigmasterol Alteration.

Sterols are isoprenoid-derived lipids that play essential structural and functional roles in eukaryotic cells. Plants produce a complex mixture of sterols, and changes in plant sterol profiles have been linked to plant-pathogen interactions. β-Sitosterol and stigmasterol, in particular, have been associated with plant defense. As nematodes have lost the ability to synthesize sterols de novo, they require sterols from the host. Tomato () plants infected by the plant parasitic nematode show a reduced level of stigmasterol and a repression of the gene , encoding the sterol C-22 desaturase that is responsible for the conversion of β-sitosterol to stigmasterol. In this study, we investigated the role of the tomato sterol C-22 desaturase gene in the response to infection by . We explored the plant-nematode interaction over time by analyzing the plant sterol composition and gene regulation in after infection. The temporal gene expression analysis showed that 3 days after inoculation with , the expression was significantly suppressed in the tomato roots, while a significant decrease in the stigmasterol content was observed after 14 days. A knockout mutant tomato line lacking stigmasterol was analyzed to better understand the role of CYP710A11 in nematode development. grown in the mutant line showed reduced egg mass counts, presumably due to the impaired growth of the mutant. However, the nematodes developed as well as they did in the wild-type line. Thus, while the suppression of expression during nematode development may be a defense response of the plant against the nematode, the lack of stigmasterol did not seem to affect the nematode. This study contributes to the understanding of the role of stigmasterol in the interaction between and tomato plants and shows that the sterol C-22 desaturase is not essential for the success of .