Physiological and Molecular Aspects of Two Thymus Species Differently Sensitive to Drought Stress

Sexually dimorphic acetyl-CoA biosynthesis and utilization in response to drought and exogenous acetic acid

Female willows exhibit greater drought tolerance and benefit more from exogenous acetic acid (AA)-improved drought tolerance than males. However, the potential mechanisms driving these sex-specific responses remain unclear. To comprehensively investigate the sexually dimorphic responsive mechanisms of willows to drought and exogenous AA, here, we performed physiological, proteomic, Lys-acetylproteomic, and transgenic analyses in female and male Salix myrtillacea exposed to drought and AA-applicated drought treatments, focusing on protein abundance and lysine acetylation (LysAc) changes. Drought-tolerant females suffered less drought-induced photosynthetic and oxidative damage, did not activate AA and acetyl-CoA biosynthesis, TCA cycle, fatty acid metabolism, and jasmonic acid signaling as strongly as drought-sensitive males. Exogenous AA caused overaccumulation of endogenous AA and inhibition of acetyl-CoA biosynthesis and utilization in males. However, exogenous AA greatly enhanced acetyl-CoA biosynthesis and utilization and further enhanced drought performance of females, possibly determining that AA improved drought tolerance more in females than in males. Interestingly, overexpression of acetyl-CoA synthetase (ACS) could reprogram fatty acids, increase LysAc levels, and improve drought tolerance, highlighting the involvement of ACS-derived acetyl-CoA in drought responses. In addition, drought and exogenous AA induced sexually dimorphic LysAc associated with histones, transcription factors, and metabolic enzymes in willows. Especially, exogenous AA may greatly improve the photosynthetic capacity of S. myrtillacea males by decreasing LysAc levels and increasing the abundances of photosynthetic proteins. While hyperacetylation in glycolysis, TCA cycle, and fatty acid biosynthesis potentially possibly serve as negative feedback to acclimate acetyl-CoA biosynthesis and utilization in drought-stressed males and AA-applicated females. Thus, acetyl-CoA biosynthesis and utilization determine the sexually dimorphic responses of S. myrtillacea to drought and exogenous AA.

Evaluation of Differentially Expressed Genes in Leaves vs. Roots Subjected to Drought Stress in Flax (Linum usitatissimum L.)

Drought stress is a common environmental challenge that plants face, severely constraining plant growth and reducing crop yield and quality. Several studies have highlighted distinct responses between monocotyledonous and dicotyledonous plants. However, the mechanisms underlying flax tolerance to abiotic stress, such as drought, remain unclear. In this study, we investigated the morphological, physiological, and biochemical characteristics and the genome-wide gene expression of oil flax and fiber flax in response to drought stress. The results revealed that drought stress caused significant wilting of flax leaves. Within the first 24 h of stress, various physiological and biochemical characteristics exhibited rapid responses. These included fresh weight, relative water content (RWC), proline, soluble protein, soluble sugar, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves or roots of flax. Additionally, drought stress led to a significant rise in lignin content in fiber flax. In addition, the transcriptome analysis demonstrated genome-wide variations in gene expression induced by drought stress. Specifically, genes associated with photosynthesis, proline biosynthesis, and phytohormone metabolism exhibited significant differences in expression levels under stress conditions in flax. These findings highlight the rapid response of flax to drought stress within a short-term period. Our experiment also revealed that, although there were variations in the levels of small compound content or gene expression between Longya10 and Fany under drought stress, most stress-resistance responses were similar. Furthermore, the results provide additional evidence supporting the existence of mechanisms underlying the response to drought stress in plants.

On the Future Perspectives of Some Medicinal Plants within Lamiaceae Botanic Family Regarding Their Comprehensive Properties and Resistance against Biotic and Abiotic Stresses

Lamiaceae is one of the largest botanical families, encompassing over 6000 species that include a variety of aromatic and medicinal spices. The current study is focused on three plants within this botanical family: basil (Ocimum basilicum L.), thyme (Thymus vulgaris L.), and summer savory (Satureja hortensis L.). These three species contain primary and secondary metabolites such as phenolic and flavonoid compounds, fatty acids, antioxidants, and essential oils and have traditionally been used for flavoring, food preservation, and medicinal purposes. The goal of this study is to provide an overview of the nutraceutical, therapeutic, antioxidant, and antibacterial key features of these three aromatics to explore new breeding challenges and opportunities for varietal development. In this context, a literature search has been performed to describe the phytochemical profile of both primary and secondary metabolites and their pharmacological uses, as well as to further explore accession availability in the medicine industry and also to emphasize their bioactive roles in plant ecology and biotic and abiotic stress adaptability. The aim of this review is to explore future perspectives on the development of new, highly valuable basil, summer savory, and thyme cultivars. The findings of the current review emphasize the importance of identifying the key compounds and genes involved in stress resistance that can also provide valuable insights for further improvement of these important medicinal plants.

Light-Dependence of Formate (C1) and Acetate (C2) Transport and Oxidation in Poplar Trees

Although apparent light inhibition of leaf day respiration is a widespread reported phenomenon, the mechanisms involved, including utilization of alternate respiratory pathways and substrates and light inhibition of TCA cycle enzymes are under active investigation. Recently, acetate fermentation was highlighted as a key drought survival strategy mediated through protein acetylation and jasmonate signaling. Here, we evaluate the light-dependence of acetate transport and assimilation in Populus trichocarpa trees using the dynamic xylem solution injection (DXSI) method developed here for continuous studies of C1 and C2 organic acid transport and light-dependent metabolism. Over 7 days, 1.0 L of [¹³C]formate and [¹³C₂]acetate solutions were delivered to the stem base of 2-year old potted poplar trees, while continuous diurnal observations were made in the canopy of CO₂, H₂O, and isoprene gas exchange together with δ¹³CO₂. Stem base injection of 10 mM [¹³C₂]acetate induced an overall pattern of canopy branch headspace ¹³CO₂ enrichment (δ¹³CO₂ +27‰) with a diurnal structure in δ¹³CO₂ reaching a mid-day minimum followed by a maximum shortly after darkening where δ¹³CO₂ values rapidly increased up to +12‰. In contrast, 50 mM injections of [¹³C]formate were required to reach similar δ¹³CO₂ enrichment levels in the canopy with δ¹³CO₂ following diurnal patterns of transpiration. Illuminated leaves of detached poplar branches pretreated with 10 mM [¹³C₂]acetate showed lower δ¹³CO₂ (+20‰) compared to leaves treated with 10 mM [¹³C]formate (+320‰), the opposite pattern observed at the whole plant scale. Following dark/light cycles at the leaf-scale, rapid, strong, and reversible enhancements in headspace δ¹³CO₂ by up to +60‰ were observed in [¹³C₂]acetate-treated leaves which showed enhanced dihydrojasmonic acid and TCA cycle intermediate concentrations. The results are consistent with acetate in the transpiration stream as an effective activator of the jasmonate signaling pathway and respiratory substrate. The shorter lifetime of formate relative to acetate in the transpiration stream suggests rapid formate oxidation to CO₂ during transport to the canopy. In contrast, acetate is efficiently transported to the canopy where an increased allocation towards mitochondrial dark respiration occurs at night. The results highlight the potential for an effective integration of acetate into glyoxylate and TCA cycles and the light-inhibition of citrate synthase as a potential regulatory mechanism controlling the diurnal allocation of acetate between anabolic and catabolic processes.

Different Seasonal Collections of Ficus carica L. Leaves Diversely Modulate Lipid Metabolism and Adipogenesis in 3T3-L1 Adipocytes

Due to the high prevalence of obesity and type 2 diabetes, adipogenesis dysfunction and metabolic disorders are common features in the elderly population. Thus, the identification of novel compounds with anti-adipogenic and lipolytic effects is highly desirable to reduce diabetes complications. Plants represent an important source of bioactive compounds. To date, the antidiabetic potential of several traditional plants has been reported, among which Ficus carica L. is one of the most promising. Considering that plant metabolome changes in response to a number of factors including seasonality, the aim of this study was to evaluate whether Ficus carica leaves extracts collected in autumn (FCa) and spring (FCs) differently modulate lipid metabolism and adipogenesis in 3T3-L1 adipocytes. The 1H-NMR profile of the extracts showed that FCs have a higher content of caffeic acid derivatives, glucose, and sucrose than FCa. In contrast, FCa showed a higher concentration of malic acid and furanocoumarins, identified as psoralen and bergapten. In vitro testing showed that only FCa treatments were able to significantly decrease the lipid content (Ctrl vs. FCa 25 μg/mL, 50 μg/mL and 80 μg/mL; p < 0.05, p < 0.01 and p < 0.001, respectively). Furthermore, FCa treatments were able to downregulate the transcriptional pathway of adipogenesis and insulin sensitivity in 3T3-L1 adipocytes. In more detail, FCa 80 μg/mL significantly decreased the gene expression of PPARγ (p < 0.05), C/EBPα (p < 0.05), Leptin (p < 0.0001), adiponectin (p < 0.05) and GLUT4 (p < 0.01). In conclusion, this study further supports an in-depth investigation of F. carica leaves extracts as a promising source of active compounds useful for targeting obesity and diabetes.

The Therapeutic Potential of Ethnomedicinally Important Anatolian Thyme Species: A Phytochemical and Biological Assessment

Thyme has been used for various therapeutic purposes in many different cultures, which makes it one of the most riveting medicinal plants throughout history. From its beneficial effects on the respiratory tract or the gastrointestinal system, to its unique skin-related activities, the investigation of the medicinal properties of thyme has always been an alluring topic for researchers aiming to develop conventional medications from this traditional herb. With an incentive to contribute to the extensive thyme research, three Thymus L. species namely Thymus cariensis Hub-Mor. & Jalas (endemic), Thymus praceox subsp. grossheimii (Ronniger) Jalas, and Thymus pubescens Boiss. et Kotschy ex Celak from Turkey were deeply investigated within this study. The analysis of the phytochemical constituents of the extracts was conducted by LC-MS/MS. 12 biologically important secondary metabolites (p-coumaric acid, caffeic acid, salicylic acid, quinic acid, fumaric acid, vanillin, malic acid, rutin, apigenin, naringenin, and nicotiflorin) were detected in all extracts. Their total phenolic and flavonoid contents were calculated (11.15 ± 0.17—61.12 ± 2.59 μg PEs/mg extract, 2.53 ± 0.04—40.28 ± 0.92 μg QEs/mg extract, respectively), and the antioxidant potential of the extracts was evaluated by DPPH and ABTS radical scavenging and CUPRAC activity methods, accordingly, the extracts were shown to possess significant antioxidant activity. Among them, Thymus cariensis Hub-Mor. & Jalas was the most active with IC₅₀ values of 34.97 ± 1.00 μg/ml and 9.98 ± 0.04 μg/ml regarding the DPPH and ABTS radical scavenging assays, respectively, and an A_0.5 value of 5.80 ± 0.02 μg/ml according to CUPRAC activity method. Their anticholinesterase, antityrosinase, and antiurease activities were also tested, Thymus cariensis Hub-Mor. & Jalas (35.61 ± 1.20%) and Thymus pubescens Boiss. et Kotschy ex Celak aerial part extract (33.49 ± 1.39%) exhibited moderate antibutyrylcholinesterase activity at 200 μg/ml concentration. The results of the cell viability assay indicated that the extracts demonstrated moderate-to-low cytotoxicity on A498 human renal cell lines. Furthermore, all studied extracts exerted noteworthy antimicrobial activity, especially against Candida tropicalis (MIC values: 19.53—78.12 μg/ml). The presented data substantiates the use of thyme extracts as therapeutic agents in both ethnomedicine and conventional therapies.

Plants' Physio-Biochemical and Phyto-Hormonal Responses to Alleviate the Adverse Effects of Drought Stress: A Comprehensive Review

Water, a necessary component of cell protoplasm, plays an essential role in supporting life on Earth; nevertheless, extreme changes in climatic conditions limit water availability, causing numerous issues, such as the current water-scarce regimes in many regions of the biome. This review aims to collect data from various published studies in the literature to understand and critically analyze plants' morphological, growth, yield, and physio-biochemical responses to drought stress and their potential to modulate and nullify the damaging effects of drought stress via activating natural physiological and biochemical mechanisms. In addition, the review described current breakthroughs in understanding how plant hormones influence drought stress responses and phytohormonal interaction through signaling under water stress regimes. The information for this review was systematically gathered from different global search engines and the scientific literature databases Science Direct, including Google Scholar, Web of Science, related studies, published books, and articles. Drought stress is a significant obstacle to meeting food demand for the world's constantly growing population. Plants cope with stress regimes through changes to cellular osmotic potential, water potential, and activation of natural defense systems in the form of antioxidant enzymes and accumulation of osmolytes including proteins, proline, glycine betaine, phenolic compounds, and soluble sugars. Phytohormones modulate developmental processes and signaling networks, which aid in acclimating plants to biotic and abiotic challenges and, consequently, their survival. Significant progress has been made for jasmonates, salicylic acid, and ethylene in identifying important components and understanding their roles in plant responses to abiotic stress. Other plant hormones, such as abscisic acid, auxin, gibberellic acid, brassinosteroids, and peptide hormones, have been linked to plant defense signaling pathways in various ways.

Salicylic Acid Stimulates Defense Systems in Allium hirtifolium Grown under Water Deficit Stress

Nowadays, the use of the growth regulator salicylic acid for improving a plant's resistance to environmental stresses such as drought is increasing. The present study investigated the effect of salicylic acid on the physiological traits, antioxidant enzymes, yield, and quality of Allium hirtifolium (shallots) under drought conditions for three years (2016-2017, 2017-2018, and 2018-2019). The experiment was conducted as a split-plot based on a randomized complete block design with four repeats. Irrigation as the main factor in four levels of 100% (full irrigation), 75% and 50% of the plant water requirements with non-irrigation (dryland), and salicylic acid as the sub-factor in four levels of 0, 0.75, and 1 mmol, were the studied factors in this research. The combined analysis of three-year data showed that drought reduced leaf relative water content (RWC), membrane stability index (MSI), chlorophyll content, onion yield, and increased activity of antioxidant enzymes, proline content, tang, and allicin of shallots. Shallot spraying with salicylic acid improved leaf RWC, MSI, chlorophyll content, and onion yield. The highest yield of onion (1427 gr m-2) belonged to full irrigation and foliar application of 1 mmol salicylic acid. The lowest yield (419.8 gr m-2) belonged to plats with non-irrigation and non-application of salicylic acid. By improving the effective physiological traits in resistance to water deficit, salicylic acid adjusted the effects of water deficit on the yield of shallots. Foliar application of 1 mmol salicylic acid in dryland and irrigation of 50% of the plant water requirement increased onion yield by 15.12% and 29.39%, respectively, compared to the control treatment without salicylic acid.

Abiotic Stresses in Plants and Their Markers: A Practice View of Plant Stress Responses and Programmed Cell Death Mechanisms

Understanding how plants cope with stress and the intricate mechanisms thereby used to adapt and survive environmental imbalances comprise one of the most powerful tools for modern agriculture. Interdisciplinary studies suggest that knowledge in how plants perceive, transduce and respond to abiotic stresses are a meaningful way to design engineered crops since the manipulation of basic characteristics leads to physiological remodeling for plant adaption to different environments. Herein, we discussed the main pathways involved in stress-sensing, signal transduction and plant adaption, highlighting biochemical, physiological and genetic events involved in abiotic stress responses. Finally, we have proposed a list of practice markers for studying plant responses to multiple stresses, highlighting how plant molecular biology, phenotyping and genetic engineering interconnect for creating superior crops.