Oleate accumulation, induced by silencing of microsomal omega-6 desaturase, declines with leaf expansion in transgenic tobacco.

All higher plants contain at least one microsomal omega-6 desaturase (FAD2), which inserts a double bond between the carbons 12 and 13 of monounsaturated oleic acid to generate polyunsaturated linoleic acid and controls most of the polyunsaturated lipid synthesis in plant cells. RNA interference can be used to silence endogenous genes by effective degradation of target transcripts. To investigate development-related silencing of the FAD2, fatty acid composition was analyzed in the context of leaf expansion in FAD2-silenced tobacco lines obtained by RNA interference technology. We observed that the increased oleate level in unexpanded leaves due to FAD2-silencing receded significantly in fully expanded leaves. The mechanism involved in this interesting phenomenon was investigated by analyses of individual lipid proportion, fatty acid composition of individual lipids, and FAD2 transcript level in the transgenic leaves at different expansion stages. Data revealed that the expansion-related FAD2-silencing effect was not due to rebound of FAD2 transcript, but rather probably due to chloroplast development with leaf expansion.