Coupling proteomics and lipidomics to unravel lipid synthesis in oats (Avena sativa L.)

Oat (Avena sativa L.) is famously known for its high oil content as compared to other cereal grains, such as barley and wheat. It also has a unique nutritional profile with high β-glucan fiber, low gluten, high protein and avenanthramides, which have been shown to provide a range of health benefits. Hence, there is a high marketing appeal for oats to be made into nutrient-enriched products. However, the high oil content of oats contributes to the formation of clumps during milling and fractionation processes, which renders oat processing very inefficient due to clogging of machinery. Therefore, there is interest from research and industry in the breeding of low-oil oats to overcome this processing barrier. To achieve this, greater depth of knowledge on the regulation of oil synthesis in oats is essential.

We optimized a complementary proteomics and lipidomics approach to investigate differences in the regulation of oil synthesis in a large cohort of genotypically and phenotypically diverse oat lines, as well as grain development series of two milling-grade variety. Prior to analysis, lipids and proteins were sequentially extracted from minute amounts of a single sample. LC-MS/MS analyses were performed on the SCIEX ZenoTOF 7600 system. Proteomics and lipidomics data were processed using Spectronaut™ and MS-DIAL respectively.

From the oat cultivars, we observed correlations between their oil contents and the abundances of several proteins involved in the lipid synthesis pathway (eg. acetyl-CoA carboxylase, 3-hydroxyacyl-ACP dehydratase and long-chain acyl-CoA synthetase). While the expression levels of triacylglycerol species were also positively correlated with oil levels, phospholipid expression exhibited an opposite trend. To provide further insights into oat oil synthesis, we analysed a grain development series (4 to 20 days after pollination) of two varieties and identified significant changes in protein and lipid profile at different stages that reflected their difference in oil content. Findings from this study can help oat breeders to better understand oat oil regulation and potentially inform breeding strategies for low-oil oats.