Seed coat phenolics and the developing silique transcriptome of Brassica carinata

Structures for nine compounds were elucidated in seed coats of two genetically related Brassica carinata lines. The yellow-seeded line accumulated monomeric kaempferols, phenylpropanoids, and lignans, while extractable and unextractable proanthocyanidins and a high-performance liquid chromatography peak containing polymeric-like quercetin/lignan structures were strongly reduced. The brown-seeded line accumulated large amounts of both types of proanthocyanidins (extractable and unextractable), as well as phenylpropanoids and lignans equivalent to the amounts in the yellow-seeded seed coats, but the brown-seeded seed coats lacked kaempferols. A Brassica napus 15K oligoarray experiment indicated that yellow-seeded siliques had more extreme gene expression changes and a 2.4-fold higher number of upregulated genes than brown-seeded siliques, including a host of transcription factors and genes with unknown function. Transcripts for six flavonoid genes (CHS, F3H, FOMT, DFR, GST, and TTG1) were lower and two (F3'H and FLS) were higher in yellow-seeded siliques, but expression of CHI, PAP1, and phenylpropanoid genes was unchanged.