Characterization of <i>FAE1</i> in the zero erucic acid germplasm of <i>Brassica rapa</i> L.

Abstract

The modification of erucic acid content in seeds is one of the major goals for quality breeding in oil-yielding Brassica species. However, few low erucic acid (LEA) resources are available, and novel LEA genetic resources are being sought. Fatty acid elongase 1 (FAE1) is the key gene that controls erucic acid synthesis. However, the mechanism for erucic acid synthesis in B. rapa lacks systematic study. Here, we isolated zero erucic acid lines from 1981 Chinese landraces of B. rapa and found that the formation of LEA is not attributable to variations in FAE1 coding sequences, as reported for B. napus, but may be attributable to the decrease in FAE1 expression. Moreover, the FAE1 promoter sequences of LEA and high erucic acid materials shared 95% similarity. Twenty-eight bases deletions (containing a 24-base AT-rich region) were identified approximately 1300 bp upstream from the FAE1 start codon in the LEA accessions. The genotype with the deletions co-segregated with the LEA trait in the segregating population. This study isolated an LEA B. rapa resource that can be exploited in Brassica cultivation. The promoter variations might modify the expression level of FAE1, and the results shed light on novel regulation mechanisms for erucic acid synthesis.

Development and validation of functional CAPS markers for the FAE genes in <i>Brassica juncea</i> and their use in marker-assisted selection

“…Several SNPs were found and majority of them were same as reported by Gupta et al (2004) . Allele-specific primers for these SNPs, as suggested by Liu et al (2012) , and promoter based marker developed by Yan et al (2015) in B. rapa failed to distinguish the low and high erucic acid containing genotypes.…”

“…Similarly, a reverse mutation from the phenylalanine to a serine residue at 282 in FAE1 gene of LEA cultivar ‘ORO’ through site directed mutagenesis restored the elongase activity and erucic acid formation ( Katavic et al 2002 ). The diploid Brassica species ( B. rapa and B. nigra ) have one copy of FAE1 gene while the amphidiploid species ( B. napus and B. juncea ) have two copies with additive effect ( Gupta et al 2004 , Lühs et al 1999 , Yan et al 2015 ). Several reports dealing with the mapping of FAE1 loci in B. napus and B. rapa are available, however, the information about the location in B. juncea is scanty.…”

“…The FAE1 gene is 1521 bp long without introns and encodes a protein of 507 amino acids ( Xu et al 2010 ). Several SNPs were reported between LEA and high erucic acid (HEA) genotypes in B. napus and B. rapa ( Wang et al 2010 , Wu et al 2008 , Yan et al 2015 ). Gupta et al (2004) found substitution-type single-nucleotide polymorphisms (SNPs) in FAE1.1 and FAE1.2 to distinguish low erucic from high erucic types in B. juncea .…”

“…SNPs which include single base substitution and small insertions/deletions, are the smallest unit of inheritance and can be used as perfect molecular markers when identified within genes underlying observed traits ( Lv et al 2013 , Uribe et al 2014 ). SNP variations could involve four different nucleotides at a particular site leading to only two different possible combinations ( Cho et al 2015 , Yan et al 2015 ). The abundance, relative stability, ubiquity and interspersed nature of SNPs make them ideal candidate molecular markers for the construction of high-density genetic maps, quantitative trait loci (QTL) fine mapping, marker-assisted breeding and genetic association studies ( Rafalski 2002 ).…”

Heterogeneous Distribution of Erucic Acid in Brassica napus Seeds

“…There are two major seed-oil types of B. napus, low-erucic acid type and high-erucic acid type. Low erucic acid content (< 2%) is a major evaluation index for edible rapeseed cultivars (Hristov et al, 2011;Yan et al, 2015), and reducing erucic acid content has been a major goal for rapeseed breeding programs (Yan et al, 2015;Zhao et al, 2019). Alternatively, cultivars of B. napus containing high erucic acid are an important resource for industrial applications (Hristov et al, 2011).…”