Differential accumulation of phenolic compounds and expression of related genes in black- and yellow-seeded Brassica napus

Abstract

Developing yellow-seeded Brassica napus (rapeseed) with improved qualities is a major breeding goal. The intermediate and final metabolites of the phenylpropanoid and flavonoid pathways affect not only oil quality but also seed coat colour of B. napus. Here, the accumulation of phenolic compounds was analysed in the seed coats of black-seeded (ZY821) and yellow-seeded (GH06) B. napus. Using toluidine blue O staining and liquid chromatography–mass spectrometry, histochemical and biochemical differences were identified in the accumulation of phenolic compounds between ZY821 and GH06. Two and 13 unique flavonol derivatives were detected in ZY821 and GH06, respectively. Quantitative real-time PCR analysis revealed significant differences between ZY821 and GH06 in the expression of common phenylpropanoid biosynthetic genes (BnPAL and BnC4H), common flavonoid biosynthetic genes (BnTT4 and BnTT6), anthocyanin- and proanthocyandin-specific genes (BnTT3 and BnTT18), proanthocyandin-specific genes (BnTT12, BnTT10, and BnUGT2) and three transcription factor genes (BnTTG1, BnTTG2, and BnTT8) that function in the flavonoid biosynthetic pathway. These data provide insight into pigment accumulation in B. napus, and serve as a useful resource for researchers analysing the formation of seed coat colour and the underlying regulatory mechanisms in B. napus.

Molecular Mapping and QTL for Expression Profiles of Flavonoid Genes in Brassica napus

“…Yellow B. napus seeds are the most desirable, as they have thinner seed coats and higher seed oil and protein contents than do the dark-seeded varieties with a similar genetic background (Olsson, 1960; Tang et al, 1997; Meng et al, 1998). Several studies have shown that seed coat color is determined by the content of the phenolic compounds cyanidin and procyanidin in B. napus (Marles and Gruber, 2004; Lepiniec et al, 2006; Qu et al, 2013). These pigments are mainly composed of polymers of proanthocyanidin (PA), which is synthesized via the flavonoid-anthocyanin-proanthocyanidin pathway (simplified as flavonoid pathway here), a core branch of the phenylpropanoid pathway (Bharti and Khurana, 2003; Gachon et al, 2005).…”

Fine Mapping and Whole-Genome Resequencing Identify the Seed Coat Color Gene in Brassica rapa

“…The observed diversity of seed coat color in rapeseed is caused by the differential accumulation of pigments in the endothelium [9,33], which is similar to the TT phenotype in A . thaliana [34,35].…”

“…Defects in different TT genes result in different degrees of variation in testa color [36]. Moreover, considering the close phylogenetic relationship between Arabidopsis and Brassica , orthologs of TT genes may play similar roles in Brassica species; quantitative analysis of gene expression supports this inference [33,38]. In A .…”

“…In B . napus , however, some TT genes are likely involved in the staining of seed coats, but there is no direct evidence indicating that one dominant TT gene controls seed coat color in these species [33,40,41]. …”

Identification and cloning of GOLDEN2-LIKE1 (GLK1), a transcription factor associated with chloroplast development in Brassica napus L.

“…The allotetraploid species B. napus, which was derived from the interspecific hybridization of two diploid species, B. rapa and B. oleracea, is an ideal model for the study of gene evolution and function. In addition, excessive gene loss is typical following polyploid formation in eukaryotes (Qu et al, 2013). In this study, all copies of GLK1 identified were verified using the homology cloning method, and each of the orthologous blocks corresponding to ancestral blocks was identified using collinearity between Brassicaceae orthologs (Table S3).…”