Functions and interaction of plant lipid signalling under abiotic stresses

Lipids signaling and unsaturation of fatty acids participate in ramie response to submergence stress and hypoxia-responsive gene regulation

Ramie is a valuable crop that produces high-quality fibers and holds promise in ecological management and potential therapeutic properties. The damage of submergence during the fertile period seriously affects the growth of ramie. This study used transcriptomics and UPLC-QTOF/MS-based lipidomics analysis to reveal the lipids remodeling and stress adaptation mechanism in ramie response to submergence. The results of subcellular distribution showed that lipids in ramie leaf cells mostly aggregate in the inter-chloroplast cytoplasm to form lipid droplets under submergence stress. High-performance thin-layer chromatography (HPTLC) and lipidomics analysis showed that the composition and content of lipids in ramie leaves significantly changed under submergence stress, and the content of fatty acids (FAs) gradually accumulated with the extension of the submergence treatment time. Further analysis revealed that the content of 18:3 (n3) Coenzyme A (C18:3-CoA) increased significantly with the prolongation of submergence stress, and the exogenous addition of C18:3-CoA activated the expression of hypoxia-responsive marker genes such as BnADH1, BnPCO2, BnADH1, and BnPDC1. These results suggest that the ramie lipid metabolism pathways were significantly affected under submergence, and the C18:3-CoA may act directly or indirectly on the hypoxia-responsive genes to activate their transcriptional activities, thereby enhancing the tolerance of ramie to submergence stress.

Metabolome regulation and restoration mechanism of different varieties of rice (Oryza sativa L.) after lindane stress

There is a lack of studies on the ability of plants to metabolize chlorinated organic pollutants (COPs) and the dynamic expression changes of metabolic molecules during degradation. In this study, hybrid rice Chunyou 927 (CY) and Zhongzheyou 8 (ZZY), traditional rice subsp. Indica Baohan 1 (BH) and Xiangzaoxian 45 (XZX), and subsp. Japonica Yangjing 687 (YJ) and Longjing 31 (LJ) were stressed by a typical COPs of lindane and then transferred to a lindane-free culture to incubate for 9 days. The cumulative concentrations in the roots of BH, XZX, CY, ZZY, YJ and LJ were 71.46, 65.42, 82.06, 80.11, 47.59 and 56.10 mg·kg-1, respectively. And the degradation ratios on day 9 were 87.89 %, 86.92 %, 94.63 %, 95.49 %, 72.04 % and 82.79 %, respectively. On the 0 day after the release of lindane stress, the accumulated lindane inhibited the normal physiological activities of rice by affecting lipid metabolism in subsp. Indica BH, amino acid metabolism and synthesis and nucleotide metabolism in hybrid CY. Carbohydrate metabolism of subsp. Japonica YJ also was inhibited, but with low accumulation of lindane, YJ regulated amino acid metabolism to resist stress. With the degradation of lindane in rice, the amino acid metabolism of BH and CY, which had high degradation ratios on day 9, was activated to compound biomolecules required for the organism to recover from the damage. Amino acid metabolism and carbohydrate metabolism were disturbed and inhibited mainly in YJ with low degradation ratios. This study provides the difference of the metabolic capacity of the metabolic capacity of different rice varieties to lindane, and changes at the molecular level and metabolic response mechanism of rice during the metabolism of lindane.

Melatonin alleviates cadmium toxicity by regulating root endophytic bacteria community structure and metabolite composition in apple

The level of cadmium (Cd) accumulation in orchard soils is increasing, and excess Cd will cause serious damage to plants. Melatonin is a potent natural antioxidant and has a potential role in alleviating Cd stress. This study aimed to investigate the effects of exogenous melatonin on a root endophyte bacteria community and metabolite composition under Cd stress. The results showed that melatonin significantly scavenged the reactive oxygen species and restored the photosynthetic system (manifested by the improved photosynthetic parameters, total chlorophyll content and the chlorophyll fluorescence parameters (Fv/Fm)), increased the activity of antioxidant enzymes (the activities of catalase, superoxide dismutase, peroxidase and ascorbate oxidase) and reduced the concentration of Cd in the roots and leaves of apple plants. High-throughput sequencing showed that melatonin increased the endophytic bacterial community richness significantly and changed the community structure under Cd stress. The abundance of some potentially beneficial endophytic bacteria (Ohtaekwangia, Streptomyces, Tabrizicola and Azovibrio) increased significantly, indicating that the plants may absorb potentially beneficial microorganisms to resist Cd stress. The metabolomics results showed that melatonin significantly changed the composition of root metabolites, and the relative abundance of some metabolites decreased, suggesting that melatonin may resist Cd stress by depleting root metabolites. In addition, co-occurrence network analysis indicated that some potentially beneficial endophytes may be influenced by specific metabolites. These results provide a theoretical basis for studying the effects of melatonin on the endophytic bacterial community and metabolic composition in apple plants.

Heterologous overexpression of Tawzy1-2 gene encoding an SK3 dehydrin enhances multiple abiotic stress tolerance in Escherichia coli and Nicotiania benthamiana

MAIN CONCLUSION

The nuclear localized TaWZY1-2 helps plants resist abiotic stress by preserving the cell's ability to remove reactive oxygen species and decrease lipid oxidation under such conditions. In light of the unpredictable environmental conditions in which food crops grow, precise strategies must be developed by crops to effectively cope with abiotic stress and minimize damage over their lifespan. A key component in this endeavor is the group II of late embryogenesis abundant (LEA) proteins, known as dehydrins, which play crucial roles in enhancing the tolerance of plants to abiotic stress. Tawzy1-2 is a dehydrin-encoding gene which is constitutively expressed in various tissues of wheat. However, the biological function of TaWZY1-2 is not yet fully understood. In this study, TaWZY1-2 was isolated and identified in the wheat genome, and its functional role in conferring tolerance to abiotic stresses was detected in both prokaryotic and eukaryotic cells. Results showed that TaWZY1-2 is a nuclear localized hydrophilic protein that accumulates in response to multiple stresses. Escherichia coli cells expressing TaWZY1-2 showed enhanced tolerance to multiple stress conditions. Overexpression of TaWZY1-2 in Nicotiania benthamiana improved growth, germination and survival rate of the transgenic plants exposed to four kinds of abiotic stress conditions. Our results show that Tawzy1-2 transgenic plants exhibit improved capability in clearing reactive oxygen species and reducing lipid degradation, thereby enhancing their resistance to abiotic stress. This demonstrates a significant role of TaWZY1-2 in mitigating abiotic stress-induced damage. Consequently, these findings not only establish a basis for future investigation into the functional mechanism of TaWZY1-2 but also contribute to the expansion of functional diversity within the dehydrin protein family. Moreover, they identify potential candidate genes for crop optimization.

Discovery of novel neutral glycosphingolipids in cereal crops: rapid profiling using reversed-phased HPLC-ESI-QqTOF with parallel reaction monitoring

This study explores the sphingolipid class of oligohexosylceramides (OHCs), a rarely studied group, in barley (Hordeum vulgare L.) through a new lipidomics approach. Profiling identified 45 OHCs in barley (Hordeum vulgare L.), elucidating their fatty acid (FA), long-chain base (LCB) and sugar residue compositions; and was accomplished by monophasic extraction followed by reverse-phased high performance liquid chromatography electrospray ionisation quadrupole-time-of-flight tandem mass spectrometry (HPLC-ESI-QqTOF-MS/MS) employing parallel reaction monitoring (PRM). Results revealed unknown ceramide species and highlighted distinctive FA and LCB compositions when compared to other sphingolipid classes. Structurally, the OHCs featured predominantly trihydroxy LCBs associated with hydroxylated FAs and oligohexosyl residues consisting of two-five glucose units in a linear 1 → 4 linkage. A survey found OHCs in tissues of major cereal crops while noting their absence in conventional dicot model plants. This study found salinity stress had only minor effects on the OHC profile in barley roots, leaving questions about their precise functions in plant biology unanswered.

Genome-wide transcriptomic and functional analyses provide new insights into the response of spring barley to drought stress

Drought is a major abiotic stress that impairs the physiology and development of plants, ultimately leading to crop yield losses. Drought tolerance is a complex quantitative trait influenced by multiple genes and metabolic pathways. However, molecular intricacies and subsequent morphological and physiological changes in response to drought stress remain elusive. Herein, we combined morpho-physiological and comparative RNA-sequencing analyses to identify core drought-induced marker genes and regulatory networks in the barley cultivar 'Giza134'. Based on field trials, drought-induced declines occurred in crop growth rate, relative water content, leaf area duration, flag leaf area, concentration of chlorophyll (Chl) a, b and a + b, net photosynthesis, and yield components. In contrast, the Chl a/b ratio, stoma resistance, and proline concentration increased significantly. RNA-sequence analysis identified a total of 2462 differentially expressed genes (DEGs), of which 1555 were up-regulated and 907 were down-regulated in response to water-deficit stress (WD). Comparative transcriptomics analysis highlighted three unique metabolic pathways (carbohydrate metabolism, iron ion binding, and oxidoreductase activity) as containing genes differentially expressed that could mitigate water stress. Our results identified several drought-induced marker genes belonging to diverse physiochemical functions like chlorophyll concentration, photosynthesis, light harvesting, gibberellin biosynthetic, iron homeostasis as well as Cis-regulatory elements. These candidate genes can be utilized to identify gene-associated markers to develop drought-resilient barley cultivars over a short period of time. Our results provide new insights into the understanding of water stress response mechanisms in barley.

Salicylic Acid Treatment and Its Effect on Seed Yield and Seed Molecular Composition of Pisum sativum under Abiotic Stress

The reproductive stage of plant development has the most critical impact on yield. Flowering is highly sensitive to abiotic stress, and increasing temperatures and drought harm crop yields. Salicylic acid is a phytohormone that regulates flowering and promotes stress resilience in plants. However, the exact molecular mechanisms and the level of protection are far from understood and seem to be species-specific. Here, the effect of salicylic acid was tested in a field experiment with Pisum sativum exposed to heat stress. Salicylic acid was administered at two different stages of flowering, and its effect on the yield and composition of the harvested seeds was followed. Plants treated with salicylic acid produced larger seed pods, and a significant increase in dry weight was found for the plants with a delayed application of salicylic acid. The analyses of the seed proteome, lipidome, and metabolome did not show any negative impact of salicylic treatment on seed composition. Identified processes that could be responsible for the observed improvement in seed yields included an increase in polyamine biosynthesis, accumulation of storage lipids and lysophosphatidylcholines, a higher abundance of components of chromatin regulation, calmodulin-like protein, and threonine synthase, and indicated a decrease in sensitivity to abscisic acid signaling.