Influence of in vitro culture conditions on glucosinolate composition of microspore-derived embryos of Brassica napus

Microspore-derived embryos (MDEs) of Brassica napus were used to study the influence of sucrose, jasmonic acid (JA), and abscisic acid (ABA) on dry weight and total glucosinolate (GSL) content as well as on specific GSLs. An improved procedure was developed to enable the detection of alkenyl and indole GSLs in single MDEs although they were cultured in medium containing 13% sucrose, where the accumulation of GSL is very low. A sucrose content of 2% and below in the culture medium of the embryos was necessary to significantly increase the total GSL content in embryos of three different rapeseed cultivars. The increase in total GSL content was caused predominantly by higher contents of the indole GSL glucobrassicin (GBC). Contents of 4-hydroxy-3-indolyl glucosinolate (4OH), neoglucobrassicin (NEO), and 4-methoxyglucobrassicin (4ME) were also increased. Alkenyl GSL content remained largely unaffected and increased significantly only in embryos cultured at the lowest tested sucrose concentration of 1%. Growing the embryos in the presence of JA did not change the alkenyl GSL content but led to a 7-fold increase in the indole GSL content. Significant increases were found for GBC, 4OH and NEO, whereas 4ME content was not affected. The JA treatment did not affect the morphology or dry weight of the MDEs. In contrast, a treatment with ABA significantly reduced the dry weight and the indole GSL content of the embryos. In the combined JA and ABA treatment, the stimulative effect of JA on indole GSL biosynthesis could not override the inhibitory effect of ABA on growth and indole GSL biosynthesis of the embryos.