The structural analysis of wheat flour glycerolipids

Fatty acid desaturases (FADs) modulate multiple lipid metabolism pathways to improve plant resistance

BACKGROUND

Biological and abiotic stresses such as salt, extreme temperatures, and pests and diseases place major constraints on plant growth and crop yields. Fatty acids (FAs) and FA- derivatives are unique biologically active substance that show a wide range of functions in biological systems. They are not only participated in the regulation of energy storage substances and cell membrane plasm composition, but also extensively participate in the regulation of plant basic immunity, effector induced resistance and systemic resistance and other defense pathways, thereby improving plant resistance to adversity stress. Fatty acid desaturases (FADs) is involved in the desaturation of fatty acids, where desaturated fatty acids can be used as substrates for FA-derivatives.

OBJECTIVE

In this paper, the role of omega-FADs (ω-3 FADs and ω-6 FADs) in the prokaryotic and eukaryotic pathways of fatty acid biosynthesis in plant defense against stress (biological and abiotic stress) and the latest research progress were summarized. Moreover' the existing problems in related research and future research directions were also discussed.

RESULTS

Fatty acid desaturases are involved in various responses of plants during biotic and abiotic stress. For example, it is involved in regulating the stability and fluidity of cell membranes, reactive oxygen species signaling pathways, etc. In this review, we have collected several experimental studies to represent the differential effects of fatty acid desaturases on biotic and abiotic species.

CONCLUSION

Fatty acid desaturases play an important role in regulating biotic and abiotic stresses.

Identification of Non-Volatile Compounds That Impact Flavor Disliking of Whole Wheat Bread Made with Aged Flours

Whole wheat flour has a shorter shelf life than refined wheat flour due to off-flavor development. An untargeted liquid chromatography/mass spectrometry (LC/MS) flavoromics approach was applied to identify compounds that negatively impact the flavor liking in whole wheat bread made from aged flours. The chemical profiles of thirteen breads made from aged flours were obtained using LC/MS and modeled by orthogonal partial least squares (OPLS) to predict flavor liking. Top predictive chemical features (negatively correlated) were identified as pinellic acid (9S,12S,13S-trihydroxy-10E-octadecenoic acid), 12,13-dihydroxy-9Z-octadecenoic acid, and 1-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine. The sensory analysis confirmed the three compounds increased the bitterness intensity of the bread samples. The formation of the trihydroxy fatty acid bitter compound, pinellic acid (9S,12S,13S-trihydroxy-10E-octadecenoic acid), was impacted by the lipoxygenase activity of the flour; however, there was no influence on the formation of 12,13-dihydroxy-9Z-octadecenoic acid or 1-(9Z,12Z-octadecadienoyl)-sn-glycero-3-phosphocholine. Additionally, the concentrations of all bitter compounds were significantly higher in bread made from aged flour versus non-aged flour.

Identification of non-volatile compounds that negatively impact whole wheat bread flavor liking

Untargeted LC-MS flavoromic analysis was utilized to identify chemical compounds that impact consumer liking of whole wheat bread. Chemical fingerprints of thirteen whole wheat breads were modeled against consumer flavor liking scores by orthogonal partial least squares (OPLS) with good fit (R²Y = 0.98) and predictive ability (Q² = 0.95). The four most predictive features (negatively correlated) were identified as 9S,12S,13S-trihydroxy-octadec-10E-enoic acid (pinellic acid), 9S,12S,13S-trihydroxy-octadeca-10E,15Z-dienoic acid, 8R*,9R*,10S*-trihydroxy-octadec-6Z-enoic acid, and 1-(octadeca-9Z,12Z-dienoyl)-sn-glycero-3-phosphocholine. Sensory validation studies including bitter threshold determination and recombination tests confirmed the contribution of these compounds to the perceived bitterness intensity of the bread samples and the overall negative impact on flavor liking. Lipoxygenase activity of the flour was reported to have a significant impact on the formation of the three bitter compounds (trihydroxy fatty acids) in the bread samples.

Adjustments of lipid pathways in plant adaptation to temperature stress

Modulation of membrane lipid composition under varying environmental conditions is an important part of plant stress adaptation. Most notably, proportional changes of lipid composition in response to temperature changes are a major cellular response to requirements of membrane fluidity adjustment. In higher plants, synthesis of glycerolipids is accomplished by 2 major pathways, the prokaryotic and eukaryotic pathway, located in the chloroplast and the endoplasmic reticulum (ER), respectively. Recently, we systematically investigated the re-adjustments of glycerolipid pathways under temperature stress at the metabolite and transcript levels using 3 plant species with distinct lipid profiles. The relative contributions of 2 pathways and lipid channeling from the ER and chloroplast were both observed in plants under temperature stress. Potential factors controlling the lipid flux were identified through transcriptome analysis.

Differentiation of Whole Grain from Refined Wheat (T. aestivum) Flour Using Lipid Profile of Wheat Bran, Germ, and Endosperm with UHPLC-HRAM Mass Spectrometry

A comprehensive analysis of wheat lipids from milling fractions of bran, germ, and endosperm was performed using ultrahigh-performance liquid chromatography-high-resolution accurate-mass multistage mass spectrometry (UHPLC-HRAM-MS(n)) with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) in both positive and negative modes. About 155 lipid compounds, including free fatty acids (FA), oxylipins, alk(en)ylresorcinols (ARs), γ-oryzanol, sphingolipids, triglycerides (TGs), diglycerides (DGs), phospholipids, and galactolipids were characterized from the three milling fractions. Galactolipids and phospholipids were proposed to be potential discriminatory compounds for refined flour, whereas γ-oryzanols, ARs, TGs, and DGs could distinguish whole wheat flour from a refined one based on principal component analysis (PCA).

Understanding the biochemical basis of temperature-induced lipid pathway adjustments in plants

Glycerolipid biosynthesis in plants proceeds through two major pathways compartmentalized in the chloroplast and the endoplasmic reticulum (ER). The involvement of glycerolipid pathway interactions in modulating membrane desaturation under temperature stress has been suggested but not fully explored. We profiled glycerolipid changes as well as transcript dynamics under suboptimal temperature conditions in three plant species that are distinctively different in the mode of lipid pathway interactions. In Arabidopsis thaliana, a 16:3 plant, the chloroplast pathway is upregulated in response to low temperature, whereas high temperature promotes the eukaryotic pathway. Operating under a similar mechanistic framework, Atriplex lentiformis at high temperature drastically increases the contribution of the eukaryotic pathway and correspondingly suppresses the prokaryotic pathway, resulting in the switch of lipid profile from 16:3 to 18:3. In wheat (Triticum aestivum), an 18:3 plant, low temperature also influences the channeling of glycerolipids from the ER to chloroplast. Evidence of differential trafficking of diacylglycerol moieties from the ER to chloroplast was uncovered in three plant species as another layer of metabolic adaptation under temperature stress. We propose a model that highlights the predominance and prevalence of lipid pathway interactions in temperature-induced lipid compositional changes.

Variation in corn (Zea mays L.) for fatty acid compositions of triglycerides and phospholipids

The percentage of linoleic acid in corn germ oil of three crosses, C103D x B73, C103D x B84, and T220 x H51, and their reciprocals was investigated. Corn germ oil from F2, F3, and backcrossed generations was also examined. More than one gene locus appeared to be involved in conditioning the linoleic acid content in these crosses. Strong maternal effects were exhibited in the F1's. Genotype also superimposed variations in fatty acid compositions within the characteristic lipid class patterns of the phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. Fatty acid placements in triglycerides, digalactosyldiglycerides, and phospholipids of one inbred, H51, were determined by lipase and phospholipase hydrolysis. The overall pattern of placement showed that the fatty acids at the 1 position were predominantly saturated saturated and those at the 2 position were predominantly unsaturated, but the fatty acid distribution was different for each individual lipid class. The molecular species of the phosphatidylcholines and phosphatidylethanolamines were separated by silver nitrate thin-layer chromatography. The major differences in the molecular species were a higher level of the dienoic-dienoic species and a lower level of the monoenoic-monoenoic species in the phosphatidylethanolamines than in the phosphatidylcholines.