Temperature effects on fatty acid composition during development of low-linolenic oilseed rape (Brassica napus L.)

Changes in Quinoa Seed Fatty Acid Profile Under Heat Stress Field Conditions

The nutritional quality of quinoa is often related to the high protein content of their seeds. However, and despite not being an oilseed crop, the oil composition of quinoa seeds is remarkable due to its profile, which shows a high proportion of polyunsaturated fatty acids (PUFAs), particularly in essential fatty acids such as linoleic (ω-6) and α-linolenic (ω-3). In line with this, this study aimed at evaluating the effect of elevated temperatures on the oil composition of different quinoa cultivars grown in the field in two consecutive years (i.e., 2017 and 2018). In 2017, heat stress episodes resulted in a reduced oil content and lower quality linked to decreased ratios of oleic acid:linoleic acid, larger omega-6 (ω-6) to omega-3 (ω-3) ratios, and lower monounsaturated fatty acid (MUFA) and higher PUFA contents. Furthermore, the correlations found between mineral nutrients such as phosphorous (P) and the contents of oleic and linoleic acids emphasize the possibility of optimizing oil quality by controlling fertilization. Overall, the results presented in this study show how the environmental and genetic factors and their interaction may impact oil quality in quinoa seeds.

High day and night temperatures distinctively disrupt fatty acid and jasmonic acid metabolism, inducing male sterility in cotton

High temperature stress is an inevitable environmental factor in certain geographical regions. To study the effect of day and night high temperature stress on male reproduction, the heat-sensitive cotton line H05 was subjected to high temperature stress. High day/normal night (HN) and normal day/high night (NH) temperature treatments were compared with normal day/normal night (NN) temperature as a control. At the anther dehiscence stage, significant differences were observed, with a reduction in flower size and filament length, and sterility in pollen, seen in NH more than in HN. A total of 36 806 differentially expressed genes were screened, which were mainly associated with fatty acid and jasmonic acid (JA) metabolic pathways. Fatty acid and JA contents were reduced more in NH than HN. Under NH, ACYL-COA OXIDASE 2 (ACO2), a JA biosynthesis gene, was down-regulated. Interestingly, aco2 CRISPR-Cas9 mutants showed male sterility under the NN condition. The exogenous application of methyl jasmonate to early-stage buds of mutants rescued the sterile pollen and indehiscent anther phenotypes at the late stage. These data show that high temperature at night may affect fatty acid and JA metabolism in anthers by suppressing GhACO2 and generate male sterility more strongly than high day temperature.

Fatty acid composition, bioactive phytochemicals, antioxidant properties and oxidative stability of edible fruit seed oil: effect of preharvest and processing factors

Fruit seed is a by-product of fruit processing into juice and other products. Despite being treated as waste, fruit seed contains oil with health benefits comparable or even higher than the conventional seed oil from field crops. In addition to essential fatty acids, the fruit seed oil is a rich source of bioactive compounds such as tocopherols, carotenoids, flavonoids, phenolic acids and phytosterols, which have been implicated in the prevention of chronic and degenerative diseases such as cancer, diabetes and cardiovascular diseases. The emerging potential of fruit seed oil application in food and nutraceuticals has prompted researchers to study the effect of preharvest and processing factors on the seed oil quality with respect to nutritional qualities, antioxidant compounds and properties. Herein, the effect of cultivar, fruit-growing region, seeds pretreatment, seeds drying and seed oil extraction on tocopherols, polyphenols, phytosterols, carotenoids, fatty acids, antioxidant activity and oxidative stability of the fruit seed oil is critically discussed. Understanding the influence of these factors on seed oil bioactive phytochemicals, nutritional qualities and antioxidant properties is critical not only for genetically improving the oilseeds plants with desired characteristics, but also in seed oil processing and value addition. Therefore, preharvest and processing factors are essential considerations when determining the application of fruit seed oil.

Fatty acid composition and desaturase gene expression in flax (Linum usitatissimum L.)

Little is known about the relationship between expression levels of fatty acid desaturase genes during seed development and fatty acid (FA) composition in flax. In the present study, we looked at promoter structural variations of six FA desaturase genes and their relative expression throughout seed development. Computational analysis of the nucleotide sequences of the sad1, sad2, fad2a, fad2b, fad3a and fad3b promoters showed several basic transcriptional elements including CAAT and TATA boxes, and several putative target-binding sites for transcription factors, which have been reported to be involved in the regulation of lipid metabolism. Using semi-quantitative reverse transcriptase PCR, the expression patterns throughout seed development of the six FA desaturase genes were measured in six flax genotypes that differed for FA composition but that carried the same desaturase isoforms. FA composition data were determined by phenotyping the field grown genotypes over four years in two environments. All six genes displayed a bell-shaped pattern of expression peaking at 20 or 24 days after anthesis. Sad2 was the most highly expressed. The expression of all six desaturase genes did not differ significantly between genotypes (P = 0.1400), hence there were no correlations between FA desaturase gene expression and variations in FA composition in relatively low, intermediate and high linolenic acid genotypes expressing identical isoforms for all six desaturases. These results provide further clues towards understanding the genetic factors responsible for FA composition in flax.

Genetic enhancement of Brassica napus seed quality

The ultimate value of the Brassica napus (canola) seed is derived from the oil fraction, which has long been recognized for its premium dietary attributes, including its low level of saturated fatty acids, high content of monounsaturated fatty acids, and favorable omega-3 fatty acid profile. However, the protein (meal) portion of the seed has also received favorable attention for its essential amino acids, including abundance of sulfur-containing amino acids, such that B. napus protein is being contemplated for large scale use in livestock and fish feed formulations. Efforts to optimize the composition of B. napus oil and protein fractions are well documented; therefore, this article will review research concerned with optimizing secondary metabolites that affect the quality of seed oil and meal, from undesirable anti-nutritional factors to highl value beneficial products. The biological, agronomic, and economic values attributed to secondary metabolites have brought much needed attention to those in Brassica oilseeds and other crops. This review focuses on increasing levels of beneficial endogenous secondary metabolites (such as carotenoids, choline and tochopherols) and decreasing undesirable antinutritional factors (glucosinolates, sinapine and phytate). Molecular genetic approaches are given emphasis relative to classical breeding.

Determination of antioxidant capacity, phenolic acids, and fatty acid composition of rapeseed varieties

Three different analytical methods: ferric-reducing antioxidant power (FRAP), 2,2'-diphenyl-1-picrylhydrazyl (DPPH), and oxygen radical absorbance capacity (ORAC) were used for determination of antioxidant capacity of seven rapeseed varieties. Antioxidant capacity and levels of the total phenolic content, individual phenolic acids, fatty acid composition, and the selected physicochemical properties of the studied rapeseed cultivars were determined. Mean ORAC values for methanolic extracts of rapeseeds (4092-12989 mmol of Trolox/100 g) were significantly higher than FRAP and DPPH values (6218-7641 and 6238-7645 mumol of Trolox/100 g, respectively). Although FRAP and DPPH results were lower than ORAC values for all studied rapeseed varieties, there are linear and significant correlations between these three analytical methods (correlation coefficients ranged between 0.9124 and 0.9930, p < 0.005). Also, total phenolic compounds in rapeseeds correlated with antioxidant capacity (correlation coefficients ranged between 0.8708 and 0.9516, p < 0.01). Total phenolic acids determined by HPLC varied from 20.3 mg to 40.7 mg per 100 g of rapeseed flour, and the main phenolic acid is sinapic acid (17.4-36.4 mg/100 g). Fatty acid composition (SAFA = 7.2-8.6%, MUFA = 58.5-68.0%, PUFA = 24.7-33.9%) and the absence of trans-fatty acids indicate that the studied rapeseed varieties can be a source of unsaturated fatty acids and have a positive impact on human health.

Warm and cold parental reproductive environments affect seed properties, fitness, and cold responsiveness in Arabidopsis thaliana progenies

Conditions in the parental environment during reproduction can affect the performance of the progenies. The goals of this study were to investigate whether warm or cold temperatures in the parental environment during flowering and seed development affect Arabidopsis thaliana seed properties, growth performance, reproduction and stress tolerance of the progenies, and to find candidate genes for progeny-related differences in stress responsiveness. Parental plants were raised at 20 degrees C and maintained from bolting to seed maturity at warm (25 degrees C) or cold (15 degrees C) temperatures. Analysis of seed properties revealed significant increases in nitrogen in seeds from warm temperature and significant increases in lipids and in the ratio of alpha-linolenic to oleic acid in seeds from the cold parental environment. Progenies of the warm parental environment showed faster germination rates, faster root elongation growth, higher leaf biomass and increased seed production at various temperatures compared with those from the cold parental environment. This indicates that under stable environmental conditions, progenies from warm parental environments had a clear adaptive advantage over those from cold parental environments. This parental effect was presumably transmitted by the higher nitrogen content of the seeds developed in warm conditions. When offspring from parents grown at different temperatures were exposed to chilling or freezing stress, photosynthetic yield recovered faster in progenies originating from cold parental environments. Cold acclimation involved up-regulation of transcripts of flavanone 3-hydroxylase (F3H) and pseudo response regulator 9 (PRR9) and down-regulation of growth-associated transcription factors (TFs) NAP and AP2domain containing RAP2.3. NAP, a regulator of senescence, and PRR9, a temperature-sensitive modulator of the circadian clock, were probably involved in mediating parent-of-origin effects, because they showed progeny-related expression differences under chilling. Because low temperatures also delay senescence, cold responsiveness of NAP suggests that this factor is linked with the regulatory network that is important for environmental acclimation of plants.

Mapping of the loci controlling oleic and linolenic acid contents and development of fad2 and fad3 allele-specific markers in canola (Brassica napus L.)

The quality of canola oil is determined by its constituent fatty acids such as oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). Most canola cultivars normally produce oil with about 55-65% oleic acid and 8-12% linolenic acid. High concentrations of linolenic acid lead to oil instability and off-type flavor, while high levels of oleic acid increase oxidative stability and nutritional value of oil. Therefore, development of canola cultivars with increased oleic acid and reduced linolenic acid is highly desirable for canola oil quality. In this study, we have mapped one locus that has a major effect and one locus that has a minor effect for high oleic acid and two loci that have major effects for low linolenic acid in a doubled haploid population. The major locus for high C18:1 was proven to be the fatty acid desaturase-2 (fad2) gene and it is located on the linkage group N5; the minor locus is located on N1. One major QTL for C18:3 is the fatty acid desaturase-3 gene of the genome C (fad3c) and it is located on N14. The second major QTL resides on N4 and is the fad3a gene of the A genome. We have sequenced genomic clones of the fad2 and fad3c genes amplified from an EMS-induced mutant and a wild-type canola cultivar. A comparison of the mutant and wild-type allele sequences of the fad2 and fad3c genes revealed single nucleotide mutations in each of the genes. Detailed sequence analyses suggested mechanisms by which both the mutations can cause altered fatty acid content. Based on the sequence differences between the mutant and wild-type alleles, two single nucleotide polymorphism (SNP) markers, corresponding to the fad2 and fad3c gene mutations, were developed. These markers will be highly useful for direct selection of desirable fad2 and fad3c alleles during marker-assisted trait introgression and breeding of canola with high oleic and low linolenic acid.