Synthesis, structural characterization and effect on human granulocyte intracellular cAMP levels of abscisic acid analogs

cAMP Is a Promising Regulatory Molecule for Plant Adaptation to Heat Stress

With gradual warming or increased frequency and magnitude of high temperature, heat stress adversely affects plant growth and eventually reduces plant productivity and quality. Plants have evolved complex mechanisms to sense and respond to heat stress which are crucial to avoiding cell damage and maintaining cellular homeostasis. Recently, 33″,55″-cyclic adenosine monophosphate (cAMP) has been proved to be an important signaling molecule participating in plant adaptation to heat stress by affecting multi-level regulatory networks. Significant progress has been made on many fronts of cAMP research, particularly in understanding the downstream signaling events that culminate in the activation of stress-responsive genes, mRNA translation initiation, vesicle trafficking, the ubiquitin-proteasome system, autophagy, HSPs-assisted protein processing, and cellular ion homeostasis to prevent heat-related damage and to preserve cellular and metabolic functions. In this present review, we summarize recent works on the genetic and molecular mechanisms of cAMP in plant response to heat stress which could be useful in finding thermotolerant key genes to develop heat stress-resistant varieties and that have the potential for utilizing cAMP as a chemical regulator to improve plant thermotolerance. New directions for future studies on cAMP are discussed.

Photostable Abscisic Acid Agonists with a Geometrically Rigid Cyclized Side Chain

The plant hormone abscisic acid (ABA) plays a central role in adaptive responses to abiotic stresses that adversely affect crop growth and productivity. However, ABA photoinstability limits its use in agriculture. To overcome this drawback, in this study, we developed photostable ABA analogues, the (+)-BP2A compound series (compounds 5-9), in which the dienoic acid side chain of ABA was replaced with phenylacetic acid. All BP2A analogues showed higher stability against UV-B irradiation at 302 nm than ABA, and compounds 6 and 7 barely decomposed even under sunlight. In physiological assays, (+)-BP2A and (+)-compound 7, in which the α,β-unsaturated carbonyl group of BP2A was reduced, exhibited ABA-like activities, including inhibition of seed germination and induced drought tolerance in Arabidopsis. Biochemical studies revealed that (+)-compound 7, unlike (+)-BP2A, did not activate pyrabactin resistance-like (PYL) receptors in vitro and was converted to (+)-BP2A in plants, suggesting that it functions as a prodrug PYL agonist. Furthermore, (+)-compound 7 inhibited seed germination of tomato, lettuce, and rice. Thus, this compound represents a potential plant growth regulator that induces ABA-type responses in agricultural fields.

Synthesis of Conjugated Dienes in Natural Compounds

This review describes the various synthetic methods commonly used to obtain molecules possessing conjugated dienes. We focus on methods involving cross-coupling reactions using various metals such as nickel, palladium, ruthenium, cobalt, cobalt/zinc, manganese, zirconium, or iron, mainly through examples that aimed to access natural molecules or their analogues. Among the natural molecules covered in this review, we discuss the total synthesis of a phytohormone, Acid Abscisic (ABA), carried out by our team involving the development of a conjugated diene chain.

A new adenylyl cyclase, putative disease-resistance RPP13-like protein 3, participates in abscisic acid-mediated resistance to heat stress in maize

In plants, 3´,5´-cyclic adenosine monophosphate (cAMP) is an important second messenger with varied functions; however, only a few adenylyl cyclases (ACs) that synthesize cAMP have been identified. Moreover, the biological roles of ACs/cAMP in response to stress remain largely unclear. In this study, we used quantitative proteomics techniques to identify a maize heat-induced putative disease-resistance RPP13-like protein 3 (ZmRPP13-LK3), which has three conserved catalytic AC centres. The AC activity of ZmRPP13-LK3 was confirmed by in vitro enzyme activity analysis, in vivo RNAi experiments, and functional complementation in the E. coli cyaA mutant. ZmRPP13-LK3 is located in the mitochondria. The results of in vitro and in vivo experiments indicated that ZmRPP13-LK3 interacts with ZmABC2, a possible cAMP exporter. Under heat stress, the concentrations of ZmRPP13-LK3 and cAMP in the ABA-deficient mutant vp5 were significantly less than those in the wild-type, and treatment with ABA and an ABA inhibitor affected ZmRPP13-LK3 expression in the wild-type. Application of 8-Br-cAMP, a cAMP analogue, increased heat-induced expression of heat-shock proteins in wild-type plants and alleviated heat-activated oxidative stress. Taken together, our results indicate that ZmRPP13-LK3, a new AC, can catalyse ATP for the production of cAMP and may be involved in ABA-regulated heat resistance.

Dumbbell-like Pt-Fe3O4 Nanoparticles Encapsulated in N-Doped Carbon Hollow Nanospheres as a Novel Yolk@Shell Nanostructure toward High-Performance Nanocatalysis

Noble metal-Fe₃O₄ dumbbell-like nanoparticles have aroused considerable attention because of their high potential as heterogeneous nanocatalysts. The designed synthesis of the advanced architecture of noble metal-Fe₃O₄ dumbbell-like nanoparticles with both improved catalytic activity and stability is still a challenge. Herein, through the combination of yolk@shell and dumbbell-like nanostructures, dumbbell-like Pt-Fe₃O₄ nanoparticles encapsulated in N-doped carbon hollow nanospheres (Pt-Fe₃O₄@N-carbon) as a special yolk@shell nanostructure were developed. In comparison with Pt-Fe₃O₄ dumbbell-like nanoparticles, Pt-Fe₃O₄@N-carbon yolk@shell nanoparticles showed improved catalytic activity and stability toward the liquid-phase 4-nitrophenol reduction and β-ionone oxidation, making them a promising candidate for catalysis applications.

Rational Discovery of (+) (S) Abscisic Acid as a Potential Antifungal Agent: a Repurposing Approach

Fungal infections are spreading widely worldwide, and the types of treatment are limited due to the lack of diverse therapeutic agents and their associated side effects and toxicity. The discovery of new antifungal classes is vital and critical. We discovered the antifungal activity of abscisic acid through a rational drug design methodology that included the building of homology models for fungal chorismate mutases and a pharmacophore model derived from a transition state inhibitor. Ligand-based virtual screening resulted in some hits that were filtered using molecular docking and molecular dynamic simulations studies. Both in silico methods and in vitro antifungal assays were used as tools to select and validate the abscisic acid repurposing. Abscisic acid inhibition assays confirmed the inhibitory effect of abscisic acid on chorismate mutase through the inhibition of phenylpyruvate production. The repositioning of abscisic acid, the well-known and naturally occurring plant growth regulator, as a potential antifungal agent because of its suggested action as an inhibitor to several fungal chorismate mutases was the main result of this work.

Solvent-Free Mizoroki-Heck Reaction Applied to the Synthesis of Abscisic Acid and Some Derivatives

Abscisic acid (ABA) is a natural product, which is a well-known phytohormone. However, this molecule has recently exhibited interesting biological activities, emphasizing the need for a simple and direct access to new analogues based on the ABA framework. Our strategy relies on a pallado-catalyzed Mizoroki-Heck cross-coupling as key reaction performed in solvent and ligand free conditions. After a careful optimization, we succeeded in accessing various (E/Z)-dienes and (E/E/Z)-trienes in moderate to good yields without isomerization and applied the same approach to the synthesis of ABA in an environmentally sound manner.

Fabrication of Se/C using carbohydrates as biomass starting materials: an efficient catalyst for regiospecific epoxidation of β-ionone with ultrahigh turnover numbers

Fabrication of Se/C catalyst from glucose as the biomass starting materials was reported for the first time, affording an efficient and regiospecific epoxidation of β-ionone.

Plant Hormones: Key Players in Gut Microbiota and Human Diseases?

It is well established that plant hormones such as auxins, cytokinins (CKs), and abscisic acid (ABA) not only govern important plant physiological traits but are key players in plant-microbe interactions. A poorly appreciated fact, however, is that both microbes and animals produce and perceive plant hormones and their mimics. Moreover, dietary plant hormones impact on human physiological process such as glucose assimilation, inflammation, and cell division. This leads us to wonder whether plant hormones could ensure functions in microbes per se as well as in animal-microbe interactions. We propose here and explore the hypothesis that plant hormones play roles in animal-microbiota relationships, with consequences for human health.

Abscisic Acid as Pathogen Effector and Immune Regulator

Abscisic acid (ABA) is a sesquiterpene signaling molecule produced in all kingdoms of life. To date, the best known functions of ABA are derived from its role as a major phytohormone in plant abiotic stress resistance. Different organisms have developed different biosynthesis and signal transduction pathways related to ABA. Despite this, there are also intriguing common themes where ABA often suppresses host immune responses and is utilized by pathogens as an effector molecule. ABA also seems to play an important role in compatible mutualistic interactions such as mycorrhiza and rhizosphere bacteria with plants, and possibly also the animal gut microbiome. The frequent use of ABA in inter-species communication could be a possible reason for the wide distribution and re-invention of ABA as a signaling molecule in different organisms. In humans and animal models, it has been shown that ABA treatment or nutrient-derived ABA is beneficial in inflammatory diseases like colitis and type 2 diabetes, which confer potential to ABA as an interesting nutraceutical or pharmacognostic drug. The anti-inflammatory activity, cellular metabolic reprogramming, and other beneficial physiological and psychological effects of ABA treatment in humans and animal models has sparked an interest in this molecule and its signaling pathway as a novel pharmacological target. In contrast to plants, however, very little is known about the ABA biosynthesis and signaling in other organisms. Genes, tools and knowledge about ABA from plant sciences and studies of phytopathogenic fungi might benefit biomedical studies on the physiological role of endogenously generated ABA in humans.

Organoselenium-catalyzed selectivity-switchable oxidation of β-ionone

The selectivities of the oxidations of β-ionone 1 were switched by the organoselenium catalyst used. [3,5-(CF₃)₂C₆H₃Se]₂ led to (E)-5,6-epoxy-β-ionone (2, 72% yield), while (PhCH₂Se)₂ gave the major Baeyer–Villiger oxidation product 3 in excellent yield (91%).