Duplicated FAD2 genes, fatty acid profiles and membrane integrity in cold stress response of durum wheat genotypes

Abstract Fatty acid desaturases (FADs) introduce double bonds at specific positions of fatty acyl chains and are involved in the protection of membrane integrity at low temperatures. Three genotypes of Triticum turgidum ssp. durum with differences in cold tolerance were considered. The analysis of TdFAD2 sequences identified an intronless gene encoding a 387 amino acid protein including three histidine domains. The in silico mapping on the cv Svevo genome revealed the occurrence of four FAD2 copies in tandem localized in 6A and 6B chromosomes and suggested an inversion in 6B. Three out of eight copies consisted of non-functional sequences. The exploration of the 5´regulatory region showed differences in TF binding sites among the copies suggesting certain specificity in gene expression. The evaluation of FAD2 by qRT-PCR, in plants exposed at 4 ˚C, showed transcriptional induction and variations among the genotypes. The fatty acid profiles determined by gas chromatography revealed that the major component of the fatty acids (60–80%) was linolenic acid (18:3). The more cold-tolerant genotypes increased 18:1 and 18:2 (the product of FAD2 ) content whereas the sensitive genotype did not show marked variations. Membrane integrity evaluated through electrolyte leakage was in accordance with phenotypic differences in cold tolerance. Our work provides information about the structure of TdFAD2 locus and the FAD2 expression and fatty acid profiles under the cold effect. Molecular and biochemical characterization of germplasm contributes to explain phenotypic variability in complex traits and thus facilitates the development of new varieties adapted to specific cultivation areas.