Down-Regulation of FAD2-1 Gene Expression Alters Lysophospholipid Composition in the Endosperm of Rice Grain and Influences Starch Properties

Abstract

Small quantities of lipids accumulate in the white rice grains. These are grouped into non-starch lipid and starch lipid fractions that affect starch properties through association with starch. Lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE) are two major lipid classes in the two fractions. Using high-oleic rice grains, we investigated the fatty-acid composition in flour and starch by LC-MS and evaluated its impact on starch properties. In the wild-type grain, nearly 50% of fatty acids in LPC and LPE were palmitic acid (C16:0), over 20% linoleic acid (C18:2) and less than 10% oleic acid (C18:1). In the high-oleic rice grain, C18:1 increased at the expense of C18:2 and C16:0. The compositional changes in starch lipids suggest that LPC and LPE are transported to an amyloplast with an origin from endoplasmic reticulum-derived PC and PE during endosperm development. The high-dissociation temperature of the amylose-lipid complex (ALC) and restricted starch swelling power in the high-oleic rice starch indicates that the stability of the ALC involving C18:1 is higher than that of C18:2 and C16:0. This study provides insight into the lipid deposition and starch properties of rice grains with optimized fatty-acid composition.

Natural Variation of Fatty Acid Desaturase Gene Affects Linolenic Acid Content and Starch Pasting Viscosity in Rice Grains

“…However, the eating quality of brown rice is usually not desirable and needs to be improved. Although fatty acids are minor components of the rice endosperm, they may play an important role in starch quality [ 27 , 28 , 29 ]. However, the effect of unsaturated fatty acids on the eating quality of rice is unclear.…”

Post-genomics revolution in the design of premium quality rice in a high-yielding background to meet consumer demands in the 21st century

“…They showed that downregulation of the major FAD2-1 resulted in increased oleic acid and reduced linoleic and palmitic acids in rice grains ( Zaplin et al., 2013 ). Luo et al. (2021a , 2021b) found that knockdown of FAD2-1 also influenced starch properties ( Luo et al., 2021a ).…”

“… Luo et al. (2021a , 2021b) found that knockdown of FAD2-1 also influenced starch properties ( Luo et al., 2021a ). Khan et al.…”

Rice Compounds with Impact on Diabetes Control

“…These complexes are formed during the synthesis of starch. They are best known for forming complexes with amylose molecules stabilized by hydrogen bounds [43,66], which inhibit the swelling of rice and reduce susceptibility to starch digestive enzymes. The study by Ye et al (2018) shows that the presence of endogenous lipids has effects on rice flour digestibility.…”

“…Triacylglycerols are the major non-starch lipids present in the rice grain; free fatty acid and lysophospholipids are the major starch lipids in the rice grain [ 43 ]. Starch lipids, although they exist in a smaller proportion, still play an important role in starch functionality and quality, affecting its digestibility by modifying starch swelling, gelatinization, and pasting [ 66 ]. These complexes are formed during the synthesis of starch.…”