Genome-wide identification and functional analysis of SGR gene family in Brassica napus L.

Chlorophyll is a kind of green pigment for plant photosynthesis, which has a direct effect on plant growth. In this study, bioinformatics methods were used to identify the members of SGR gene family in Brassica napus, Brassica rapa, Brassica oleracea, and Arabidopsis thaliana. Most of the 28 SGR genes contained four exons, encoding basic proteins. Chromosome mapping and syntenic analysis showed that there was no tandem duplication in the SGR gene family members of Brassica napus. SGR gene family members had a linear relationship, highly homologous in evolution, and very conserved in the evolutionary process. Moreover, a genome-wide association study (GWAS) of chlorophyll content was performed using a Brassica 60K Illumina Infinium SNP array in 203 Brassica napus accessions. Two haplotype regions (Chr.A01: 6,193,165--6,317,757 bp and Chr.C01: 9,059,861--9,906,618 bp) carrying two SGR genes (BnaSGR1a-A01 and BnaSGR1-C01) were detected, which were significantly associated with chlorophyll content. Meanwhile, the regional association analysis of 50 resequenced rapeseed inbred lines revealed that a SNP located in exon 2 of BnaSGR1a-A01 significantly associated with chlorophyll content. Co-expression network analysis revealed that BnaSGR1a-A01 were directly linked with BnaSGR2-A03, and indirectly linked with BnaSGR1-C01, BnaSGR1-A08, BnaSGR2-C03, BnaSGR1-C07, BnaSGRL-C06, and BnaSGRL-A10, thus forming a molecular network involved in the potential regulation of chlorophyll content. Chlorophyll a, chlorophyll b, and the total chlorophyll content of T2 Arabidopsis transgenic plants overexpressing BnasSGR1a-A01 were significantly lower than wild type, indicating that BnaSGR1a-A01 regulated chlorophyll degradation. This study laid a foundation for the functional research and utilization of SGR gene in Brassica napus L. [ABSTRACT FROM AUTHOR]