Recovery from chilling modulates the acyl-editing of phosphatidic acid molecular species in barley roots (Hordeum vulgare L.)

Quality assessment of flax advanced breeding lines varying in seed coat color and their potential use in the food and industrial applications

BACKGROUND

With the increasing consumer awareness of the strong relationship between food and health, flax became a promising functional food due to its bioactive nutraceutical composition. Intra-specific crosses of eight contrasting flax genotypes were performed previously, and within segregating F6 progeny families, we investigated a close-up composition of phytochemicals derived from whole seeds.

RESULTS

The considerable genetic variation among the flax F6 families suggested that intra-specific hybridization is essential in flax breeding to obtain and broaden genetic variability and largely affirmed the opportunity for selecting promising lines. Also, significant variations in the targeted metabolite contents and antioxidant properties were observed among brown and yellow-seeded families. Notably, brown-seeded families expressed the highest average values of saturated fatty acids, protein, fiber, tocopherol, phenolics, SDG, and SECO lignans. Yellow-seeded families represented the highest average content of unsaturated fatty acids and mucilage. The cultivation year significantly affects flaxseed's composition and functional properties, presumably due to temperature, humidity, and sunshine time differences. Interestingly, the seeds obtained in warmer conditions were more potent and had more chemical constituents. The favorable genetic correlations among all evaluated traits suggest the possibility of joint genetic selection for several nutritional and phytochemical characteristics in flax. The current study highlights the importance and utilization of 19 top families as their seeds and oil play imperative roles in the pharmaceuticals and food industries. The antioxidant capacity of the seeds showed that families 84B, 23B, 35Y, 95Y, 30B, 88B, and 78B serve as a natural source of dietary antioxidants beneficial to human health. To increase the oxidative stability of the flaxseed oil, the quality evaluation identified some families with low levels of linolenic acid.

CONCLUSIONS

These findings are essential to improving flaxseed's nutritional quality and therapeutic properties through a bulk breeding program.

Lipid signaling and proline catabolism are activated in barley roots (Hordeum vulgare L.) during recovery from cold stress

Previous findings have shown that phospholipase D (PLD) contributes to the response to long-term chilling stress in barley by regulating the balance of proline (Pro) levels. Although Pro accumulation is one of the most prominent changes in barley roots exposed to this kind of stress, the regulation of its metabolism during recovery from stress remains unclear. Research has mostly focused on the responses to stress per se, and not much is known about the dynamics and mechanisms underlying the subsequent recovery. The present study aimed to evaluate how PLD, its product phosphatidic acid (PA), and diacylglycerol pyrophosphate (DGPP) modulate Pro accumulation in barley during recovery from long-term chilling stress. Pro metabolism involves different pathways and enzymes. The rate-limiting step is mediated by pyrroline-5-carboxylate synthetase (P5CS) in its biosynthesis, and by proline dehydrogenase (ProDH) in its catabolism. We observed that Pro levels decreased in recovering barley roots due to an increase in ProDH activity. The addition of 1-butanol, a PLD inhibitor, reverted this effect and altered the relative gene expression of ProDH. When barley tissues were treated with PA before recovery, the fresh weight of roots increased and ProDH activity was stimulated. These data contribute to our understanding of how acidic membrane phospholipids like PA help to control Pro degradation during recovery from stress.

Comparative transcriptomes reveal molecular mechanisms of apple blossoms of different tolerance genotypes to chilling injury

Apple (Malus domestica, Borkh.) is one of the four largest fruits in the world. Freezing damage during the flowering period of apples is one of the main factors leading to the reduction or even extinction of apple production. Molecular breeding of hardy apples is a good solution to these problems. However, the current screening of cold tolerance genes still needs to be resolved. Therefore, in this article, the transcriptome detection and cold tolerance gene screening during the cold adaptation process of apple were studied in order to obtain potential cold-resistant genes. Herein, two high-quality apple tree species (Malus robusta Rehd and M. domestica) were used for cold adaptation experiments and studied under different low-temperature stress conditions (0, -2 and -4°C). The antioxidant levels of two apple flower tissues were tested, and the transcriptome of the flowers after cold culture was tested by next-generation sequencing technology. Antioxidant test results show that the elimination of peroxides in M. robusta Rehd and the adjustment of the expression of antioxidant enzymes promote the cold resistance of this variety of apples. Functional enrichment found that the expression of enzyme activity, cell wall and cell membrane structure, glucose metabolism/gluconeogenesis, and signal transmission are the main biological processes that affect the differences in the cold resistance characteristics of the two apples. In addition, three potential cold-resistant genes AtERF4, RuBisCO activase 1, and an unknown gene (ID: MD09G1075000) were screened. In this study, three potential cold-resistant genes (AtERF4, RuBisCO activase 1, and an unknown gene [ID: MD09G1075000]) and three cold-repressed differential genes (AtDTX29, XTH1, and TLP) were screened.

Using MetaboAnalyst to introduce undergraduates to lipidomic analysis and lipid remodeling in barley roots

Lipidomics is a discipline that focuses on the identification and quantification of lipids. Although a part of the larger omics field, lipidomics requires specific approaches for the analysis and biological interpretation of datasets. This article presents a series of activities for introducing undergraduate microbiology students to lipidomic analysis through tools from the web-based platform MetaboAnalyst. The students perform a complete lipidomic workflow, which includes experiment design, data processing, data normalization, and statistical analysis of molecular phospholipid species obtained from barley roots exposed to Fusarium macroconidia. The input data are provided by the teacher, but students also learn about the methods through which they were originally obtained (untargeted liquid chromatography coupled with mass spectrometry). The ultimate aim is for students to understand the biological significance of phosphatidylcholine acyl editing. The chosen methodology allows users who are not proficient in statistics to make a comprehensive analysis of quantitative lipidomic datasets. We strongly believe that virtual activities based on the analysis of such datasets should be incorporated more often into undergraduate courses, in order to improve students' data-handling skills for omics sciences.

Biophysical Properties of Lipid Membranes from Barley Roots during Low-Temperature Exposure and Recovery

Glycerolipid remodeling, a dynamic mechanism for plant subsistence under cold stress, has been posited to affect the biophysical properties of cell membranes. In barley roots, remodeling has been observed to take place upon exposure to chilling stress and to be partially reverted during stress relief. In this study, we explored the biophysical characteristics of membranes formed with lipids extracted from barley roots subjected to chilling stress, or during a subsequent short- or long-term recovery. Our aim was to determine to what extent barley roots were able to offset the adverse effects of temperature on their cell membranes. For this purpose, we analyzed the response of the probe Laurdan inserted in bilayers of different extracts, the zeta potential of liposomes, and the behavior of Langmuir monolayers upon compression. We found important changes in the order of water molecules, which is in agreement with the changes in the unsaturation index of lipids due to remodeling. Regarding Langmuir monolayers, we found that films from all the extracts showed a reorganization at a surface pressure that depends on temperature. This reorganization occurred with an increase in entropy for extracts from control plants and without entropy changes for extracts from acclimated plants. In summary, some membrane properties were recovered after the stress, while others were not, suggesting that the membrane biophysical properties play a role in the mechanism of plant acclimation to chilling. These findings contribute to our understanding of the impact of lipid remodeling on biophysical modifications in plant roots.

Do betaine lipids replace phosphatidylcholine as fatty acid editing hubs in microalgae?

Acyl editing refers to a deacylation and reacylation cycle on a lipid, which allows for fatty acid desaturation and modification prior to being removed and incorporated into other pools. Acyl editing is an important determinant of glycerolipid synthesis and has been well-characterized in land plants, thus this review begins with an overview of acyl editing in plants. Much less is known about acyl editing in algae, including the extent to which acyl editing impacts lipid synthesis and on which lipid substrate(s) it occurs. This review compares what is known about acyl editing on its major hub phosphatidylcholine (PC) in land plants with the evidence for acyl editing of betaine lipids such as diacylglyceryltrimethylhomoserine (DGTS), the structural analog that replaces PC in several species of microalgae. In land plants, PC is also known to be a major source of fatty acids and diacylglycerol (DAG) for synthesis of the neutral lipid triacylglycerol (TAG). We review the evidence that DGTS contributes substantially to TAG accumulation in algae as a source of fatty acids, but not as a precursor to DAG. We conclude with evidence of acyl editing on other membrane lipid substrates in plants and algae apart from PC or DGTS, and discuss future analyses to elucidate the role of DGTS and other betaine lipids in acyl editing in microalgae.

LC-HR/MS Analysis of Lipophilic Extracts from Calendula arvensis (Vaill.) L. Organs: An Unexplored Source in Cosmeceuticals

As part of a project aimed at promoting the use of Calendula arvensis (Vaill.) L. (field marigold, Asteraceae) phytocomplexes in cosmeceutical formulations, the chemical composition in apolar specialized metabolites is herein elucidated. Furthermore, the screening of the cytotoxicity of the apolar extracts was evaluated in order to underline their safety as functional ingredients for cosmetics. After dissection of Calendula organs (florets, fruits, leaves, bracts, stems, and roots), ultrasound-assisted maceration in n-hexane as an extracting solvent allowed us to obtain oil-like mixtures, whose chemical composition has been highlighted through a UHPLC-ESI-QqTOF-MS/MS approach. Twenty-nine metabolites were tentatively identified; different compounds, among which the well-known poly-unsaturated fatty acids, and oxylipins and phosphatides were detected for the first time in Calendula genus. The screening of the dose-response cytotoxicity of the apolar extracts of C. arvensis highlighted the concentration of 10 μg/mL as the most suitable for the formulation of cosmeceutical preparations. Sera enriched with leaf and fruit apolar extracts turned out to have the best activity, suggesting it can be used as a new source in skin care thanks to their higher content in fatty acids.

The Electrostatic Basis of Diacylglycerol Pyrophosphate—Protein Interaction

Diacylglycerol pyrophosphate (DGPP) is an anionic phospholipid formed in plants, yeast, and parasites under multiple stress stimuli. It is synthesized by the phosphorylation action of phosphatidic acid (PA) kinase on phosphatidic acid, a signaling lipid with multifunctional properties. PA functions in the membrane through the interaction of its negatively charged phosphomonoester headgroup with positively charged proteins and ions. DGPP, like PA, can interact electrostatically via the electrostatic-hydrogen bond switch mechanism but differs from PA in its overall charge and shape. The formation of DGPP from PA alters the physicochemical properties as well as the structural dynamics of the membrane. This potentially impacts the molecular and ionic binding of cationic proteins and ions with the DGPP enriched membrane. However, the results of these important interactions in the stress response and in DGPP’s overall intracellular function is unknown. Here, using ³¹P MAS NMR, we analyze the effect of the interaction of low DGPP concentrations in model membranes with the peptides KALP23 and WALP23, which are flanked by positively charged Lysine and neutral Tryptophan residues, respectively. Our results show a significant effect of KALP23 on the charge of DGPP as compared to WALP23. There was, however, no significant effect on the charge of the phosphomonoester of DGPP due to the interaction with positively charged lipids, dioleoyl trimethylammonium propane (DOTAP) and dioleoyl ethyl-phosphatidylcholine (EtPC). Divalent calcium and magnesium cations induce deprotonation of the DGPP headgroup but showed no noticeable differences on DGPP’s charge. Our results lead to a novel model for DGPP—protein interaction.