Salt stress-induced protein pattern associated with photosynthetic parameters and andrographolide content in Andrographis paniculata Nees

Application of proteomics in investigating the responses of plant to abiotic stresses

MAIN CONCLUSION

This review summarizes the application of proteomic techniques in investigating the responses of plant to abiotic stresses. In the natural environment, the plants are exposed to a diverse range of adverse abiotic factors that significantly impact their growth and development. The plants have evolved intricate stress response mechanisms at the genetic, protein, metabolic, and phenotypic levels to mitigate damage caused by unfavorable conditions. Proteomics serves as an effective tool for studying protein changes in plants and provides valuable insights into the physiological mechanisms underlying plant stress resistance. Several proteins involved in abiotic stress responses have been identified in plants, including transcription factors, protein kinases, ATP synthases, heat shock proteins, redox proteins, and enzymes in secondary metabolite pathways. Medicinal plants are a unique category of crops capable of synthesizing secondary metabolites, which play a crucial role in resisting abiotic stress and exhibit changes in content under stress conditions. In this review, we present an overview of proteomic tools employed for investigating the responses of plants to abiotic stresses and summarize alterations observed at the protein level under various abiotic stresses such as signal transduction, oxidative damage, carbohydrate and energy metabolism, protein and amino acid metabolism, cellular homeostasis, and enzyme involvement in secondary metabolism. This work aims to facilitate the application of proteomics techniques in plants research while enhancing our understanding of the response mechanisms exhibited by these plants towards abiotic stresses.

The ability of low levels of elevated ozone to change the growth and phytochemical constituents of a medicinal plant Andrographis paniculata (Burm. f.) Nees

Ground-level ozone (O3) is well recognized as a secondary air pollutant with detrimental effects on plant growth and biochemistry. In a field study, Andrographis paniculata (King of Bitter) was exposed to ambient O3 and elevated O3 (AO + 20 ppb) at three growth stages [45, 90, and 135 days after treatment, (DAT)] using open-top chambers. Elevated O3 stress negatively impacted plant growth, increased cell damage, and induced foliar injuries. However, elevated O3 also boosted antioxidant production such as proline, phenol, and enzymatic antioxidants, as well as certain secondary metabolites such as tannins, phytosterols, saponins, and alkaloids. This may enhance the plant's medicinal properties, including compounds limonene dioxide, phytol, palmitic acid, and androstadiene. While, certain metabolites like Citronellol, Khusenol, and tocopherol displayed an adverse reaction under elevated O3 exposure. The novel detection of acrodiene, squalene, and neophytadiene under O3 stress emphasizes their medicinal significance. Notably, an important bioactive compound andrographolide in A. paniculata showed increased synthesis under elevated O3 at 45 and 90 DAT, suggesting that O3 exposure could enhance the plant's pharmaceutical value.

Dihydroporphyrin iron (III) enhances low temperature tolerance by increasing carbon and nitrogen metabolism in Andrographis paniculata

Dihydroporphyrin iron (DH-Fe) is a novel plant growth regulator that plays significant roles in plant stress resistance. We found that Andrographis paniculata is extremely sensitive to low temperature (LT) with a threshold of 25°C. To evaluate whether and how DH-Fe alleviates LT stress in A. paniculata, different DH-Fe concentrations (0, 10, 20, and 40 μg·L-1) were applied to estimate its effects on C and N metabolism and antioxidative capacity in A. paniculata grown under 20°C. Pre-treatment of DH-Fe alleviated LT-induced anthocyanin accumulation. Additionally, it relieved LT-induced oxidative stress by increasing the activity of catalase (CAT). DH-Fe reduced the contents of sucrose, soluble sugar and starch and the activities of sucrose synthase (SS) and hexokinase (HXK), but stimulated the activities of sucrose phosphate synthase (SPS), glucose-6-phosphate dehydrogenase (G6PDH), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), phosphoenolpyruvate carboxylase (PEPC), isocitrate dehydrogenase (ICDH), and malic enzyme (ME). Soluble protein and proline contents were decreased by DH-Fe, while total N and free amino acids contents were increased, accompanying by the enhancement of the activities of glutamine synthase (GS), glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GTP). Simultaneously, the content of andrographolide, the bioactive ingredient of A. paniculata, was remarkably declined. These results indicated that DH-Fe alleviates LT-induced oxidation by increasing sugar catabolism and allocating C metabolic flow to N assimilation. A concentration of 20 μg·L-1 DH-Fe is recommended to be used to enhance LT tolerance in A. paniculata. Our results update the understanding of the mechanism of plant cold tolerance and provide new ideas for relieving plant cold damage.

Targeting TLR4 and regulating the Keap1/Nrf2 pathway with andrographolide to suppress inflammation and ferroptosis in LPS-induced acute lung injury

Acute lung injury (ALI) is a severe inflammatory condition with a high mortality rate, often precipitated by sepsis. The pathophysiology of ALI involves complex mechanisms, including inflammation, oxidative stress, and ferroptosis, a novel form of regulated cell death. This study explores the therapeutic potential of andrographolide (AG), a bioactive compound derived from Andrographis, in mitigating Lipopolysaccharide (LPS)-induced inflammation and ferroptosis. Our research employed in vitro experiments with RAW264.7 macrophage cells and in vivo studies using a murine model of LPS-induced ALI. The results indicate that AG significantly suppresses the production of pro-inflammatory cytokines and inhibits ferroptosis in LPS-stimulated RAW264.7 cells. In vivo, AG treatment markedly reduces lung edema, decreases inflammatory cell infiltration, and mitigates ferroptosis in lung tissues of LPS-induced ALI mice. These protective effects are mediated via the modulation of the Toll-like receptor 4 (TLR4)/Kelch-like ECH-associated protein 1(Keap1)/Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. Molecular docking simulations identified the binding sites of AG on the TLR4 protein (Kd value: -33.5 kcal·mol-1), and these interactions were further corroborated by Cellular Thermal Shift Assay (CETSA) and SPR assays. Collectively, our findings demonstrate that AG exerts potent anti-inflammatory and anti-ferroptosis effects in LPS-induced ALI by targeting TLR4 and modulating the Keap1/Nrf2 pathway. This study underscores AG's potential as a therapeutic agent for ALI and provides new insights into its underlying mechanisms of action.

Andrographolide Inhibits Inflammatory Cytokines Secretion in LPS-Stimulated RAW264.7 Cells through Suppression of NF-κB/MAPK Signaling Pathway

Andrographolide, the main active component extracted from Andrographis paniculata (Burm.f.) Wall. ex Nees, exerts anti-inflammatory effects; however, the principal molecular mechanisms remain unclear. The objective of this study was to investigate the molecular mechanisms of Andrographolide in modifying lipopolysaccharide- (LPS-) induced signaling pathway in RAW264.7 cells. An in vitro model of inflammation was induced by LPS in mouse RAW264.7 cells in the presence of Andrographolide. The concentration and expression levels of proinflammatory cytokines were determined by an enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. The nuclear level of NF-κB was measured by an electrophoretic mobility shift assay (EMSA). The expression levels of NF-κB, p38, ERK, and JNK were determined by western blot. Andrographolide dose-dependently inhibited the release and mRNA expression of TNF-α, IL-6, and IL-1β in LPS-stimulated RAW264.7 cells. The nuclear level of p65 protein was decreased in Andrographolide treatment group. Western blot analysis showed that Andrographolide suppressed LPS-induced NF-κB activation and the phosphorylation of IkBa, ERK1/2, JNK, and p38. These results suggest that Andrographolide exerts an anti-inflammatory effect by inhibiting the activation of NF-κB/MAPK signaling pathway and the induction of proinflammatory cytokines.

Genoproteomics-assisted improvement of Andrographis paniculata: toward a promising molecular and conventional breeding platform for autogamous plants affecting the pharmaceutical industry

Andrographis paniculata (Burm. f.) Wall. ex Nees. (AP) is a hermaphroditic, self-compatible, and habitual inbreeding plant. Its main bioactive component is andrographolide, which is capable of inducing autophagic cell death in some human cancer cells and helps fight HIV/AIDS. Increasing the andrographolide content by investigating the genetic mechanisms controlling its biosynthesis in order to improve and develop high-yielding cultivars are the main breeding targets for AP. However, there might exist some limitations or barriers for crossability within AP accessions. Recently, this problem was addressed in AP by using a combination of crossbreeding and biotechnology-aided genetic methods. This review emphasizes that development of a breeding platform in a hard-to-breed plant, such as AP, requires the involvement of a broad range of methods from classical genetics to molecular breeding. To this end, a phenological stage (for example, flowering and stigma development) can be simplified to a quantitative morphological trait (for example, bud or stigma length) to be used as an index to express the highest level of receptivity in order to manage outcrossing. The outcomes of the basic crossability research can be then employed in diallel mating and crossbreeding. This review explains how genomic data could produce useful information regarding genetic distance and its influence on the crossability of AP accessions. Our review indicates that co-dominant DNA markers, such as microsatellites, are also capable of resolving the evolutionary pathway and cryptic features of plant populations and such information can be used to select the best breeding strategy. This review also highlights the importance of proteomic analysis as a breeding tool. In this regard, protein diversification, as well as the impact of normal and stress-responsive proteins on morphometric and physiological behaviors, could be used in breeding programs. These findings have immense potential for improving plant production and, therefore, can be regarded as prospective breeding platforms for medicinal plants that have an autogamous mode of reproduction. Finally, this review suggests that novel site-directed genome editing approaches such as TALENs (Transcription Activator-Like Effector Nucleases) and CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR-associated protein-9 nuclease) systems together with other new plant breeding technologies (NPBT) should simultaneously be taken into consideration for improvement of pharmaceutical plants.