Fatty acid composition and desaturase gene expression in flax (Linum usitatissimum L.)

Abstract

Little is known about the relationship between expression levels of fatty acid desaturase genes during seed development and fatty acid (FA) composition in flax. In the present study, we looked at promoter structural variations of six FA desaturase genes and their relative expression throughout seed development. Computational analysis of the nucleotide sequences of the sad1, sad2, fad2a, fad2b, fad3a and fad3b promoters showed several basic transcriptional elements including CAAT and TATA boxes, and several putative target-binding sites for transcription factors, which have been reported to be involved in the regulation of lipid metabolism. Using semi-quantitative reverse transcriptase PCR, the expression patterns throughout seed development of the six FA desaturase genes were measured in six flax genotypes that differed for FA composition but that carried the same desaturase isoforms. FA composition data were determined by phenotyping the field grown genotypes over four years in two environments. All six genes displayed a bell-shaped pattern of expression peaking at 20 or 24 days after anthesis. Sad2 was the most highly expressed. The expression of all six desaturase genes did not differ significantly between genotypes (P = 0.1400), hence there were no correlations between FA desaturase gene expression and variations in FA composition in relatively low, intermediate and high linolenic acid genotypes expressing identical isoforms for all six desaturases. These results provide further clues towards understanding the genetic factors responsible for FA composition in flax.Electronic supplementary materialThe online version of this article (doi:10.1007/s13353-014-0222-0) contains supplementary material, which is available to authorized users.

Genetic diversity of SAD and FAD genes responsible for the fatty acid composition in flax cultivars and lines

“…FAD3A and FAD3B expression correlated with the accumulation of linolenic acid and the mRNA level of FAD3B was higher than that of FAD3A [12,15,16]. However, in the work of Thambugala and Cloutier, for flax genotypes with identical isoforms of SAD1, SAD2, FAD2A, FAD2B, FAD3A, and FAD3B genes but diverse content of fatty acids (OLE -11.4-21.8%, LIO -9.9-14.9%, LIN -53.7-71.9%), no correlations between the expression of desaturase genes and oil composition were revealed [14]. Polymorphisms in SAD and FAD genes were shown to be associated with the fatty acid composition [10,17].…”

“…Two paralogous genes, SAD1 and SAD2 , have three exons and two introns with a total length of 2665 and 2592 bp respectively and encode 396-residue proteins; paralogous FAD2A and FAD2B are intronless with a length of 1137 bp ( FAD2A ) and 1149 bp ( FAD2B ) and encode proteins of 378 and 382 amino acid residues respectively; FAD3A and FAD3B are also paralogous with six exons and five introns with a total length of 3280 bp ( FAD3A ) and 3002 bp ( FAD3B ) and encode proteins of 392 and 391 amino acid residues respectively [ 10 , 12 ]. SAD1 and SAD2 genes have differential expression in flax: mRNA level of SAD1 was lower and more constant between seed development stages and genotypes than that of SAD2 [ 12 – 14 ]. It was supposed that FAD2B plays role in LIO accumulation, while FAD2A is important for the complete conversion of OLE to LIO [ 12 ].…”

Oil quality in sea‐level quinoa as determined by cultivar‐specific responses to temperature and radiation conditions

“…Changes in fatty acid composition have been associated with temperature conditions during the seed‐filling period because of their regulation of the activity of desaturase enzymes . It has been demonstrated that the level of fatty acid unsaturation is inversely associated with growth temperature during seed development .…”

“…It has been demonstrated that the level of fatty acid unsaturation is inversely associated with growth temperature during seed development . As a rule, a decrease in the unsaturation level occurs when the temperature is high during seed development . However, oilseed crops showed specific responses to temperature as this condition weakly affected the proportion of unsaturated fatty acids in safflower ( Carthamus tinctorius ) and castor bean ( Ricinus communis ), moderately in soybean ( Glycine max ), rapeseed ( Brassica napus ) and maize ( Zea mays ), and strongly in sunflower ( Helianthus annuus ) …”

Adapt your shuttling proteins for virulence: a lesson from the corn smut fungus Ustilago maydis

“…Another example of a well‐known plant protein family being hijacked by a fungal pathogen was recently reported in Fusarium oxysporum , which secretes an analog of the small regulatory peptide rapid alkalinization factor (RALF) as a virulence factor during infection (Masachis et al ., ). It will also be interesting to test the role of Scp2 proteins in other basidiomycete pathogens such as the rust fungus Melampsora lini , which infects flax, a plant species representing a rich source of polyunsaturated fatty acids (Thambugala & Cloutier, ). Currently, the functional role of apoplastic Scp2 in U. maydis awaits further elucidation.…”