A truncated FatB resulting from a single nucleotide insertion is responsible for reducing saturated fatty acids in maize seed oil

Abstract

We identified a G-nucleotide insertion in a maize FatB responsible for reducing saturated fatty acids through QTL mapping and map-based cloning and developed an allele-specific DNA marker for molecular breeding. Vegetable oils with reduced saturated fatty acids have signficant health benefits. SRS72NE, a Dow AgroSciences proprietory maize inbred line, was found to contain signficantly reduced levels of palmitic acid and total saturated fatty acids in seed oil when compared to other common inbreds. Using F2 and F3 populations derived from a cross between SRS72NE and a normal inbred SLN74, we have demonstrated that the reduced saturated fatty acid phenotype in SRS72NE is controlled by a single QTL on chromosome 9 that explains 79.1 % of palmitic acid and 79.6 % total saturated fatty acid variations. The QTL was mapped to an interval of 105 kb that contains one single gene, a type B fatty acyl-ACP thioesterase (ZmFatB; GRMZM5G829544). ZmFatB alleles from SRS72NE and common inbreds were cloned and sequenced. SRS72NE fatb allele contains a single nucleotide (G) insertion in the 6th exon, which creates a premature stop codon 22 base pairs down stream. As a result, ZmFatB protein from SRS72NE is predicted to contain eight altered and 90 deleted amino acids at its C-terminus. Because the affected region is part of the conserved acyl-ACP thioesterase catalytic domain, the truncated ZmFatB in SRS72NE is likely non-functional. We also show that fatb RNA level in SRS72NE is reduced by 4.4-fold when compared to the normal allele SNL74. A high throughput DNA assay capable of differentiating the normal and reduced saturate fatty acid alleles has been developed and can be used for accelerated molecular breeding.

Fine-mapping and cross-validation of QTLs linked to fatty acid composition in multiple independent interspecific crosses of oil palm

“…In contrast, the phenotypic data for levels of C16:0 had a strong negative correlation with C18:1 levels which indicates that a reduction of C16:0 is associated with increased C18:1. This was also observed in maize seeds where a mutated FATB allele caused a dramatic reduction of C16:0 in the oil and increased the level of unsaturated FAs [ 47 ]. The truncated FATB was reported responsible for the non-functioning of a critical catalytic domain and this could have resulted in the channelling of more C16:0-ACP for elongation and subsequent desaturation into unsaturated acyl chains, such as C18:1-ACP.…”

“…A similar role was reported for PATE/FATB in oil biosynthesis in cotton seed [ 45 ]. Apart from a strong substrate preference for C16:0, the substrate specificity of palmitoyl-ACP thioesterase also extends to other saturated acyl-ACPs, including C14:0- and C18:0-ACPs [ 46 , 47 ]. This was shown in other species by over-expression of PATE/FATB in Arabidopsis thaliana [ 48 , 49 ] and canola seeds [ 50 ] which also had an elevated concentration of C14:0.…”

Transcriptome analysis identifies genes related to the waxy coating on blueberry fruit in two northern-adapted rabbiteye breeding populations

“…The gene is a blueberry homolog to acyl-[acyl-carrier-protein] hydrolase, also called the FatB gene in Arabidopsis . In maize, insertions in the FatB gene (GRMZM5G829544) have been shown to result in reduced palmitic acid (16:0) content in the seeds [27, 28]. In Arabidopsis , a T-DNA insertion in the FatB gene (AT1G08510) has been shown to result in lower levels of palmitate (16:0) and stearate (18:0) in various tissue types, resulting in a reduction in growth rate.…”

RppM, Encoding a Typical CC-NBS-LRR Protein, Confers Resistance to Southern Corn Rust in Maize

“…The development of specific markers for R genes and their application in MAS should significantly improve breeding efficiency and shorten the number of required breeding years. Many functional genes have been successfully deployed for the improvement of important traits and MAS in maize ( Ning et al, 2011 ; Chai et al, 2012 ; Zhou et al, 2012 ; Zheng et al, 2014 ), but this has not been true to the same extent with SCR owing to the lack of R genes and corresponding specific markers. In our study, we accordingly compared the CDS of the RppM allele among resistant and susceptible inbred lines and developed 24 KASP markers using different SNPs ( Supplementary Table 3 ).…”