Coumarin-Caged Compounds of 1-Naphthaleneacetic Acid as Light-Responsive Controlled-Release Plant Root Stimulators

Genome-Wide Association Studies Reveal That the Abietane Diterpene Isopimaric Acid Promotes Rice Growth through Inhibition of Defense Pathways

Plants are an important source for the discovery of novel natural growth regulators. We used activity screening to demonstrate that treatment of Nipponbare seeds with 25 μg/mL isopimaric acid significantly increased the resulting shoot length, root length, and shoot weight of rice seedlings by 11.37 ± 5.05%, 12.96 ± 7.63%, and 27.98 ± 10.88% and that it has a higher activity than Gibberellin A3 (GA3) at the same concentration. A total of 213 inbred lines of different rice lineages were screened, and we found that isopimaric acid had different growth promotional activities on rice seedlings of different varieties. After induction with 25 μg/mL isopimaric acid, 15.02% of the rice varieties tested showed increased growth, while 15.96% of the varieties showed decreased growth; the growth of the remaining 69.02% did not show any significant change from the control. In the rice varieties showing an increase in growth, the shoot length and shoot weight significantly increased, accounting for 21.88% and 31.25%. The root length and weight significantly increased, accounting for 6.25% and 3.13%. Using genome-wide association studies (GWASs), linkage disequilibrium block, and gene haplotype significance analysis, we identified single nucleotide polymorphism (SNP) signals that were significantly associated with the length and weight of shoots on chromosomes 2 and 8, respectively. After that, we obtained 17 candidate genes related to the length of shoots and 4 candidate genes related to the weight of shoots. Finally, from the gene annotation data and gene tissue-specific expression; two genes related to this isopimaric acid regulation phenotype were identified as OsASC1 (LOC_Os02g37080) on chromosome 2 and OsBUD13 (LOC_Os08g08080) on chromosome 8. Subcellular localization analysis indicated that OsASC1 was expressed in the plasma membrane and the nuclear membrane, while OsBUD13 was expressed in the nucleus. Further RT-qPCR analysis showed that the relative expression levels of the resistance gene OsASC1 and the antibody protein gene OsBUD13 decreased significantly following treatment with 25 μg/mL isopimaric acid. These results suggest that isopimaric acid may inhibit defense pathways in order to promote the growth of rice seedlings.

Application of TNB in dual photo-controlled release of phenamacril, imidacloprid, and imidacloprid synergist

Pesticides can improve crops' yield and quality, but unreasonable applications of pesticides lead to waste of pesticides which are further accumulated in the environment and threaten human health. Developing the release of controlled drugs can improve the utilization rate of pesticides. Among these methods, light-controlled release is a new technology of controlled release, which can realize spatiotemporal delivery of drugs by light. Four compounds, named Imidacloprid-Thioacetal o-nitrobenzyl-Phenamacril (IMI-TNB-PHE), Imidacloprid-Thioacetal o-nitrobenzyl- Imidacloprid (IMI-TNB-IMI), Phenamacril-Thioacetal o-nitrobenzyl-Phenamacril (PHE-TNB-PHE), and Imidacloprid-Thioacetal o-nitrobenzyl-Imidacloprid Synergist (IMI-TNB-IMISYN), were designed and synthesized by connecting thioacetal o-nitrobenzyl (TNB) with pesticides TNB displaying simple and efficient optical properties in this work. Dual photo-controlled release of pesticides including two molecules of IMI or PHE, both IMI and PHE, as well as IMI and IMISYN were, respectively, studied in this paper. Insecticidal/fungicidal activities of the photosensitive pesticides showed 2-4 times increments if they were exposed to light. In addition, a synergistic effect was observed after the light-controlled release of IMI-TNB-IMISYN, which was consistent with the effect of IMISYN. The results demonstrated whether dual photo-controlled release of the same or different pesticide molecules could be achieved with a TNB linker with spatiotemporal precision. We envisioned that TNB will be an innovative photosensitive protective group for light-dependent application of agrochemicals in the future.

o-Nitrobenzyl-Based Caged exo-16,17-Dihydro-gibberellin A5-13-acetate for Photocontrolled Release of Plant Growth Regulators

Caged plant growth regulators (caged PGRs) that release bioactive molecules under irradiation are critical in enhancing the efficacy and mitigating the negative environmental effects of PGRs. The synthetically derived plant growth inhibitor exo-16,17-dihydro-gibberellin A5-13-acetate (DHGA5) regulates the development and stress resilience of plants. We report here the conception of novel caged DHGA5 derivatives wherein the photoremovable protecting groups (PRPGs) serve not only to enable light-controlled release but also to protect the carboxyl group during chemical synthesis. Three o-nitrobenzyl-based caged DHGA5 derivatives with different substituents on the nitrobenzyl moiety were obtained and evaluated for their properties in vitro and in vivo. The photolysis half-life values of caged DHGA5 derivatives 7a, 7b, and 7c under a UV lamp were 15.6 h, 1.2 h, and 28.2 h, respectively. Experiments in vivo showed that 0.2 mM of the caged compounds significantly inhibited the growth of the model plant Arabidopsis thaliana and important crop rice in a precise photoactivated form.

Advances in nanoparticle and organic formulations for prolonged controlled release of auxins

Plant hormones have been well known since Charles Darwin as signaling molecules directing plant metabolism. Their action and transport pathways are at the top of scientific interest and were reviewed in many research articles. Modern agriculture applies phytohormones as supplements to achieve desired physiological plant response. Auxins are a class of plant hormones extensively used for crop management. Auxins stimulate the formation of lateral roots and shoots, seed germination, while extensively high concentrations of these chemicals act as herbicides. Natural auxins are unstable; light or enzyme action leads to their degradation. Moreover, the concentration dependant action of phytohormones denier one-shot injection of these chemicals and require constant slow additive of supplement. It obstructs the direct introduction of auxins. On the other hand, delivery systems can protect phytohormones from degradation and provide a slow release of loaded drugs. Moreover, this release can be managed by external stimuli like pH, enzymes, or temperature. The present review is focused on three auxins: indole-3-acetic, indole-3-butyric, and 1-naphthaleneacetic acids. We collected some examples of inorganic (oxides, Ag, layered double hydroxides) and organic (chitosan, organic formulations) delivery systems. The action of carriers can enhance auxin effects via protection and targeted delivery of loaded molecules. Moreover, nanoparticles can act as nano fertilizers, intensifying the phytohormone effect, providing slow controlled release. So delivery systems for auxins are extremely attractive for modern agriculture opening sustainable management of plant metabolism and morphogenesis.

The mechanism of coumarin inhibits germination of ryegrass (Lolium perenne) and its application as coumarin-carbon dots nanocomposites

BACKGROUND

As an important plant allelochemical, coumarin can effectively inhibit the germination of various seeds. However, little is known about the inhibition mechanism of coumarin on weed seed germination. Moreover, the herbicidal activity of coumarin is needed to be improved as a natural pesticide.

RESULTS

Coumarin had the highest inhibition effect on the ryegrass (Lolium perenne) seed, where coumarin disturbed the hormone pathway by decreasing the content of gibberellic acid 3, resulting in the reduction of amylase activity and consumption of starch during the germination process of ryegrass seed. Moreover, coumarin induced decreased activity of catalase and subsequently led to the accumulation of hydrogen peroxide and malondialdehyde, causing oxidative stress during the germination process of ryegrass seed. Furthermore, to enhance the herbicidal activity of coumarin, carbon dots (CDs) modified with polyetherimide were prepared, characterized, and then combined with coumarin to form coumarin-carbon dots (Cm-CDs) nanocomposites. Compared with coumarin, Cm-CDs nanocomposites significantly increased the herbicidal activity of coumarin on ryegrass, which implies that Cm-CDs nanocomposites could be used as a potential formulation to improve the herbicidal activity of coumarin.

CONCLUSION

This study not only reveals the mechanism of coumarin on ryegrass germination, but also develop Cm-CDs nanocomposites to enhance the herbicidal activity of coumarin. Our findings will stimulate the application of Cm-CDs nanomaterials as an effective and environmentally friendly formulation in agriculture. © 2023 Society of Chemical Industry.

The Light-Controlled Release of 2-fluoro-l-fucose, an Inhibitor of the Root Cell Elongation, from a nitrobenzyl-caged Derivative

Glycan metabolic engineering is a powerful tool for studying the glycosylation in living plant cells. The use of modified monosaccharides such as deoxy or fluorine-containing glycosides has been reported as a powerful pharmacological approach for studying the carbohydrate metabolism. 1,3,4-tri-O-acetyl-2-fluoro-l-fucose (2F-Fuc) is a potent inhibitor of the plant cell elongation. After feeding plant seedlings with 2F-Fuc, this monosaccharide derivative is deacetylated and converted by the endogenous metabolic machinery into the corresponding nucleotide-sugar, which then efficiently inhibits Golgi-localized fucosyltransferases. Among plant cell wall polymers, defects in the fucosylation of the pectic rhamnogalacturonan-II cause a decrease in RG-II dimerization, which in turn induce the arrest of the cell elongation. In order to perform the inhibition of the cell elongation process in a spatio-temporal manner, we synthesized a caged 3,4-di-O-acetyl-1-hydroxy-2-fluoro-l-fucose (1-OH-2F-Fuc) derivative carrying a photolabile ortho-nitrobenzyl alcohol function at the anomeric position: 3,4-di-O-acetyl-1-ortho-nitrobenzyl-2-fluoro-l-fucose (2F-Fuc-NB). The photorelease of the trapped 1-OH-2F-Fuc was performed under a 365 nm LED illumination. We demonstrated that the in planta elimination by photoexcitation of the photolabile group releases free 2F-Fuc in plant cells, which in turn inhibits in a dose-dependent manner and, reversibly, the root cell elongation.

Effects of Naphthaleneacetic Acid, Indole-3-Butyric Acid and Zinc Sulfate on the Rooting and Growth of Mulberry Cuttings

The mulberry tree (Morus alba) is a perennial and fast-growing tree distributed worldwide under different climatic conditions. Most of the world’s silk production (>90%) is facilitated by the feeding of silkworm larvae on the leaves of mulberry (Morus alba L.) varieties. Therefore, exploration of the protocol for improving the propagation efficiency and increasing the reproductive capacity of M. alba varieties could be of great significance. This study aimed to determine the effect of four concentrations (0, 100, 200 and 400 mg L−1) each of naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA), and zinc sulfate (0, 100 and 200 mg L−1), supplied separately or combined, on the rooting and growth of mulberry cuttings. M. alba cuttings were immersed for 5 s in each solution using the quick-dip method and subsequently, the cuttings were dried and planted in plastic pots and maintained in a greenhouse for 60 days. The number of leaves (NL), longest root size (LRS), longest stem size (LSS), number of rooted cuttings (NRC), number of stems per tree (NSP), rooting percentage (RP), wet root weight (WRW), dry root weight (DRW), wet stem weight (WSW), dry stem weight (DSW), wet leaf weight (WLW) and dry leaf weight (DLW) were evaluated. The results obtained showed an increase in all growth parameters of the mulberry cuttings. Treatments of hormones (IBA and NAA) and Zn sulfate were effective on LSS, LRS and WSW. The highest values of LSS were obtained for the treatments T5, T6, T14, T15, T16 and T18. Moreover, T5, T12 and T10 showed the highest values of LRS. The highest value of WSW was observed for T18, T5, T14, T15 and T16. The highest values of WLW and DLW were observed in T20 and T14. Dry stem weight (DSW) was high in T18 and T14. The application of NAA (at 200 mg L−1), IBA (200 and 400 mg L−1) and Zn sulfate (200 and 400 mg L−1), either alone or in double combination, can be a suitable and reliable method for mulberry propagation.

Caged Phytohormones: From Chemical Inactivation to Controlled Physiological Response

Plant hormones, also called phytohormones, are small signaling molecules regulating a wide range of growth and developmental processes. These unique compounds respond to both external (light, temperature, water, nutrition, or pathogen attack) and internal factors (e.g., age) and mediate signal transduction leading to gene expression with the aim of allowing plants to adapt to constantly changing environmental conditions. Within the regulation of biological processes, individual groups of phytohormones act mostly through a web of interconnected responses rather than linear pathways, making elucidation of their mode of action in living organisms quite challenging. To further progress with our knowledge, the development of novel tools for phytohormone research is required. Although plenty of small molecules targeting phytohormone metabolic or signaling pathways (agonists, antagonists, and inhibitors) and labeled or tagged (fluorescently, isotopically, or biotinylated) compounds have been produced, the control over them in vivo is lost at the time of their administration. Caged compounds, on the other hand, represent a new approach to the development of small organic substances for phytohormone research. The term "caged compounds" refers to light-sensitive probes with latent biological activity, where the active molecule can be freed using a light beam in a highly spatio/temporal-, amplitude-, or frequency-defined manner. This review summarizes the up-to-date development in the field of caged plant hormones. Research progress is arranged in chronological order for each phytohormone regardless of the cage compound formulation and bacterial/plant/animal cell applications. Several known drawbacks and possible directions for future research are highlighted.

Photocrosslinking of DNA using 4-methylpyranocarbazole nucleoside with thymine base selectivity

This report describes a novel photocrosslinker, 4-methylpyranocarbazole nucleoside (^MEPK), that can be induced to crosslink using visible light. Previously, we reported a visible light-responsive artificial nucleic acid, pyranocarbazole nucleoside (^PCX). ^MEPK can selectively photocrosslink to thymine bases in a complementary nucleic acid strand. It was synthesized by introducing a methyl group at the 4-position of ^PCX, and it can differentiate between thymine and cytosine. The previously reported visible light-responsive artificial nucleic acid ^PCX has a low synthetic yield. ^MEPK was synthesized by Pechmann condensation which suppressed by-product formation, making the synthesis more efficient, and resulting in a higher yield than that of ^PCX. ^MEPK is expected to have practical applications as a photocrosslinker that can be manipulated with visible light and that selectively targets thymine bases.

Multiple Roles of Mesoporous Silica in Safe Pesticide Application by Nanotechnology: A Review

Pollution related to pesticides has become a global problem due to their low utilization and non-targeting application, and nanotechnology has shown great potential in promoting sustainable agriculture. Nowadays, mesoporous silica-based nanomaterials have garnered immense attention for improving the efficacy and safety of pesticides due to their distinctive advantages of low toxicity, high thermal and chemical stability, and particularly size tunability and versatile functionality. Based on the introduction of the structure and synthesis of different types of mesoporous silica nanoparticles (MSNs), the multiple roles of mesoporous silica in safe pesticide application using nanotechnology are discussed in this Review: (i) as nanocarrier for sustained/controlled delivery of pesticides, (ii) as adsorbent for enrichment or removal of pesticides in aqueous media, (iii) as support of catalysts for degradation of pesticide contaminants, and (iv) as support of sensors for detection of pesticides. Several scientific issues, strategies, and mechanisms regarding the application of MSNs in the pesticide field are presented, with their future directions discussed in terms of their environmental risk assessment, in-depth mechanism exploration, and cost-benefit consideration for their continuous development. This Review will provide critical information to related researchers and may open up their minds to develop new advances in pesticide application.