Annual ryegrass modulates gene expression in cold environments to enhance synthesis of monounsaturated and saturated fatty acids

Context Low temperatures alter biochemical routes, modifying plant fatty acid profile. Aim This study investigated the effect of low temperature on the fatty acid profile and gene expression of acetyl-coA carboxylase alpha (ACACAα), myristoil-acyl carrier protein thioesterase (MACPT) and stearoyl-acyl-carrier-protein 9-desaturase 5 (DESAT5) in diploid and tetraploid annual ryegrass (Lolium multiflorum L.), cultivated in two locations with contrasting temperatures (colder vs warmer). Methods Pasture sampling was conducted, total RNA extraction and complementary DNA synthesis were performed and quantitative real-time PCR (RT-qPCR) was performed. Key results The average temperature was lower in colder than warmer location (8.4°C vs 18.4°C, P = 0.001). The abundance of mRNA of ACACAα was reduced by 45, whrereas MACPT increased by 352% (P = 0.001) for the colder location and diploid cultivar. The abundance of DESAT5 was increased by 61.5% (P = 0.0001) and 27% at the colder location and diploid cultivar (P = 0.002) respectively. The fatty acids C14:0, C16:1 and C18:1 were found in higher concentrations mainly on diploid cultivar at the colder location. Conclusion The adaptation of annual ryegrass to a colder environment increased medium-chain saturated fatty acids and lower melting-point monounsaturated fatty acids, caused by reduced expression of ACACAα and increased expression of MACPT and DESAT5. Implications Genotypes with enhanced expression of cold-responsive lipid metabolism genes could be selected for greater cold tolerance, improving pasture productivity in temperate climates increasing medium-chain saturated and monounsaturated fatty acids under cold stress changing forage lipid composition, which could affect animal nutrition and animal products quality.