Jasmonic Acid Pathway in Plants 2.0

Effects of Jasmonic Acid on Stress Response and Quality Formation in Vegetable Crops and Their Underlying Molecular Mechanisms

The plant hormone jasmonic acid plays an important role in plant growth and development, participating in many physiological processes, such as plant disease resistance, stress resistance, organ development, root growth, and flowering. With the improvement in living standards, people have higher requirements regarding the quality of vegetables. However, during the growth process of vegetables, they are often attacked by pests and diseases and undergo abiotic stresses, resulting in their growth restriction and decreases in their yield and quality. Therefore, people have found many ways to regulate the growth and quality of vegetable crops. In recent years, in addition to the role that JA plays in stress response and resistance, it has been found to have a regulatory effect on crop quality. Therefore, this study aims to review the jasmonic acid accumulation patterns during various physiological processes and its potential role in vegetable development and quality formation, as well as the underlying molecular mechanisms. The information provided in this manuscript sheds new light on the improvements in vegetable yield and quality.

The role of phytomelatonin in plant homeostasis, signaling, and crosstalk in abiotic stress mitigation

In recent years, there has been an increase in the study of phytomelatonin. Having numerous functions in animals, melatonin produced by plants (phytomelatonin) is also a multi-regulatory molecule with great potential in plant physiology and in mitigating abiotic stresses, such as drought, salinity, chilling, heat, chemical contamination, and UV-radiation stress. This review highlights the primary functions of phytomelatonin as an anti-stress molecule against abiotic stress. We discuss the role of phytomelatonin as a master regulator, oxidative stress manager, reactive oxygen species and reactive nitrogen species regulator, and defense compounds inducer. Although there exist a handful of reviews on the crosstalk of phytomelatonin with other signaling molecules like auxin, cytokinin, gibberellin, abscisic acid, ethylene, nitric oxide, jasmonic acid, and salicylic acid, this review looks at studies that have reported a few aspects of phytomelatonin with newly discovered signaling molecules along with classical signaling molecules with relation to abiotic stress tolerance. The research and applications of phytomelatonin with hydrogen sulfide, strigolactones, brassinosteroids, and polyamines are still in their nascent stage but hold a promising scope for the future. Additionally, this review states the recent developments in the signaling of phytomelatonin with nitrogen metabolism and nitrosative stress in plants.

A TaSnRK1α Modulates TaPAP6L-Mediated Wheat Cold Tolerance through Regulating Endogenous Jasmonic Acid

Here, a sucrose non-fermenting-1-related protein kinase alpha subunit (TaSnRK1α-1A) is identified as associated with cold stress through integration of genome-wide association study, bulked segregant RNA sequencing, and virus-induced gene silencing. It is confirmed that TaSnRK1α positively regulates cold tolerance by transgenes and ethyl methanesulfonate (EMS) mutants. A plastid-lipid-associated protein 6, chloroplastic-like (TaPAP6L-2B) strongly interacting with TaSnRK1α-1A is screened. Molecular chaperone DJ-1 family protein (TaDJ-1-7B) possibly bridged the interaction of TaSnRK1α-1A and TaPAP6L-2B. It is further revealed that TaSnRK1α-1A phosphorylated TaPAP6L-2B. Subsequently, a superior haplotype TaPAP6L-2B30S /38S is identified and confirmed that both R30S and G38S are important phosphorylation sites that influence TaPAP6L-2B in cold tolerance. Overexpression (OE) and EMS-mutant lines verified TaPAP6L positively modulating cold tolerance. Furthermore, transcriptome sequencing revealed that TaPAP6L-2B-OE lines significantly increased jasmonic acid (JA) content, possibly by improving precursor α-linolenic acid contributing to JA synthesis and by repressing JAR1 degrading JA. Exogenous JA significantly improved the cold tolerance of wheat plants. In summary, TaSnRK1α profoundly regulated cold stress, possibly through phosphorylating TaPAP6L to increase endogenous JA content of wheat plants.

Melatonin enhances drought tolerance by affecting jasmonic acid and lignin biosynthesis in wheat (Triticum aestivum L.)

Drought severely affects the yield of wheat (Triticum aestivum L.), which is mainly grown in arid and semi-arid regions. Melatonin plays an important role in various types of stress resistance in plants, including drought resistance. However, the molecular mechanism through which melatonin affects drought tolerance remains largely unknown. In this study, we revealed that melatonin (100 μM) significantly improved drought resistance during the maturation stage of Chinese Spring, Shi4185, and Hanxuan10 varieties, but not Chang6878. Further physiological, transcriptomic, and proteomic data analysis at the wheat seedling stage revealed that melatonin increased jasmonic acid (JA) content, upregulating the expression of JA genes (LOX1.5 and LOX2.1) and two transcription factors (HY5 and MYB86) under drought conditions. It also upregulated genes related to lignin biosynthesis (4CL2, P5CS1, and CCR2) as well as starch and sucrose metabolism (PME53 and SUS4). Additionally, melatonin alleviated photosynthetic and cell membrane damage caused by drought stress through maintaining low levels of hydrogen peroxide. The current results elucidate melatonin-regulated pathways in wheat and provide evidence for using melatonin as a potential biostimulant to improve wheat drought resistance under field conditions in the future.

Lipo-chitooligosaccharide and thuricin 17 act as plant growth promoters and alleviate drought stress in Arabidopsis thaliana

Lipo-chito-oligosaccharide (LCO-from Bradyrhizobium japonicum) and thuricin 17 (Th17-from Bacillus thuringiensis) are bacterial signal compounds from the rhizosphere of soybean that have been shown to enhance plant growth in a range of legumes and non-legumes. In this study, an attempt to quantify phytohormones involved in the initial hours after exposure of Arabidopsis thaliana to these compounds was conducted using UPLC-ESI-MS/MS. A petri-plate assay was conducted to screen for drought stress tolerance to PEG 8000 infusion and plant growth was studied 21-days post-stress. Arabidopsis thaliana plants grown in trays with drought stress imposed by water withhold were used for free proline determination, elemental analysis, and untargeted proteomics using LC-MS/MS studies. At 24 h post-exposure to the signal compounds under optimal growth conditions, Arabidopsis thaliana rosettes varied in their responses to the two signals. While LCO-treated rosettes showed a decrease in total IAA, cytokinins, gibberellins, and jasmonic acid, increases in ABA and SA was very clear. Th17-treated rosettes, on the other hand, showed an increase in IAA and SA. Both treatments resulted in decreased JA levels. Under severe drought stress imposed by PEG 8000 infusion, LCO and Th17 treatments were found to significantly increase fresh and dry weight over drought-stressed control plates, indicating that the presence of the signaling compounds decreased the negative effects experienced by the plants. Free proline content increased in LCO- and Th17-treated plants after water-withhold drought stress. Elemental analysis showed a significant increase in carbon percentage at the lower concentration of Th17. Untargeted proteomics revealed changes in the levels of drought-specific ribosomal proteins, glutathione S-transferase, late embryogenesis proteins, vegetative storage proteins 1 and 2, thaumatin-like proteins, and those related to chloroplast and carbon metabolism. The roles of some of these significantly affected proteins detected under drought stress are discussed.

Indole-3-Carboxylic Acid From the Endophytic Fungus Lasiodiplodia pseudotheobromae LPS-1 as a Synergist Enhancing the Antagonism of Jasmonic Acid Against Blumeria graminis on Wheat

The discovery of natural bioactive compounds from endophytes or medicinal plants against plant diseases is an attractive option for reducing the use of chemical fungicides. In this study, three compounds, indole-3-carbaldehyde, indole-3-carboxylic acid (3-ICA), and jasmonic acid (JA), were isolated from the EtOAc extract of the culture filtrate of the endophytic fungus Lasiodiplodia pseudotheobromae LPS-1, which was previously isolated from the medicinal plant, Ilex cornuta. Some experiments were conducted to further determine the antifungal activity of these compounds on wheat powdery mildew. The results showed that JA was much more bioactive than indole-3-carbaldehyde and 3-ICA against Blumeria graminis, and the disease severity caused by B. graminis decreased significantly with the concentration increase of JA treatment. The assay of the interaction of 3-ICA and JA indicated that there was a significant synergistic effect between the two compounds on B. graminis in each of the ratios of 3-ICA to JA (3-ICA:JA) ranging from 1:9 to 9:1. When the compound ratio of 3-ICA to JA was 2:8, the synergistic coefficient was the highest as 22.95. Meanwhile, a histological investigation indicated that, under the treatment of JA at 500 μg/ml or 3-ICA:JA (2:8) at 40 μg/ml, the appressorium development and haustorium formation of B. graminis were significantly inhibited. Taken together, we concluded that JA plays an important role in the infection process of B. graminis and that 3-ICA as a synergist of JA enhances the antagonism against wheat powdery mildew.