Table 1

Primers used in this study"

Table 2

SGR gene information"

Fig. 1

Phylogenetic tree of SGR gene family in Brassica napus, Brassica rapa, Brassica oleracea, and Arabidopsis thaliana"

Fig. 2

Systematic comparative analysis of SGR genes of Arabidopsis thaliana, Brassica rapa, Brassica oleracea, and Brassica napus chromosomes"

Fig. 3

Distribution of SGR genes in Brassica rapa, Brassica oleracea, and Brassica napus chromosomes The numbers of chromosomes are labeled on the left side of each chromosome. A and C are the chromosomes from Brassica rapa and Brassica oleracea; chrA and chrC are the chromosomes of the A-subgenomes and C-subgenomes from Brassica napus, respectively. Random means genes are distributed randomly to the specific chromosome, and chrCnn is unanchored scaffold that cannot be mapped to a specific chromosome from the C-subgenomes."

Fig. 4

Syntenic analysis of SGR genes in Brassica napus, Brassica oleracea, Brassica rapa, and Arabidopsis thaliana Syntenic analysis between Brassica napus showed by pink lines. Syntenic analysis between Brassica napus, Brassica rapa, and Brassica oleracea are indicated by green lines. Syntenic analysis among Arabidopsis thaliana, Brassica napus, Brassica rapa, and Brassica oleracea are indicated by brown lines."

Fig. 5

Genome-wide association study of chlorophyll content at seedling and bolting stages in 203 rapeseed accessions Haplotype region (6,193,165-6,317,757 bp) and haplotype region (9,059,861-9,906,618 bp) were significant association with chlorophyll content. In these haplotype regions carrying two orthologues of Arabidopsis gene BnaSGR1a-A01 (BnaA01g12570D) and BnaSGR1-C01 (BnaC01g14360D) are involved in chlorophyll biosynthesis process. The heat map spans the SNP markers in LD with the most strongly associated SNPs. The horizontal red dotted line represents the significant threshold (-log10(P)=4). ss_GH: chlorophyll content index in seedling stage (glasshouse experiments, 2012), bs_GH: chlorophyll content index in bolting stage (glasshouse experiments, 2012)."

Fig. 6

Association analysis of candidate genes for chlorophyll content within whole-genome resequencing of 50 accessions A: the regional association analysis of chlorophyll content in haplotype region (6,193,165-6,312,172 bp; r2=0.55). The blue dotted line indicates a threshold P-value of 1.0×10-3 for genome-wide significance. B: SNP chrA01:6306874 locates in exon two region of BnaSGR1a-A01 gene showed associated with chlorophyll content. C and D: the comparative analysis of allele G and T related to gene expression and chlorophyll content. Allele frequency greater than 0.05 in the population will be used for this analysis. The box plot showed that the allele G corresponding to inbred lines had higher chlorophyll content and gene expression level."

Fig. 7

Overexpression of BnaSGR1a-A01 in Arabidopsis A: the schematic diagram of the overexpresed vector backbone; B: the comparison of one-month seedling age true leaves (No. 4-6) of Col-0 and OE lines, bar:5 mm; C: the qRT-PCR detection of Col-0 and OE lines; D-F: the determination of chlorophyll a, chlorophyll b and total chlorophyll in Col-0 and OE lines; Col-0: non-transgenic plant; OE-BnaSGR1-13,OE-BnaSGR1-14: transgenic plant. *: P < 0.05; **: P < 0.01. Error bars indicate the standard derivations."

Fig. 8

Co-expression network analysis of BnaSGR1a-A01 genes A: the co-expression network of BnaSGR1a-A01 in the silique of Brassica napus. Red nodes represent BnaSGR genes, turquoise triangle node represent these genes directly correlation with BnaSGR genes. B: the partly co-expression network of BnaSGR1a-A01 in the silique of Brassica napus. Based on the functional annotation, the genes in the BnaSGR1a-A01 co-expression network are classified into the following three groups: chlorophyll (light blue nodes), photosystem (turquoise nodes), and transcription factors (darkolivegreen nodes). C: GO pathway of BnaSGR1a-A01 co-expression networks. Deep yellow represents that BnaSGR1a-A01 is significant correlation with these metabolism process."