Improvement of Bioactive Polyphenol Accumulation in Callus of Salvia atropatana Bunge.

Callus cultures of the Iranian medicinal plant Salvia atropatana were initiated from three-week-old seedlings on Murashige and Skoog (MS) medium supplemented with α-naphthaleneacetic acid (NAA) and various cytokinins. Although all tested hormonal variants of the medium and explant enabled callus induction, the most promising growth was noted for N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU)-induced calli. Three lines obtained on this medium (cotyledon line-CL, hypocotyl line-HL, and root line-RL) were preselected for further studies. Phenolic compounds in the callus tissues were identified using UPLC-MS (ultra-performance liquid chromatography-mass spectrometry) and quantified with HPLC (high-performance liquid chromatography). All lines exhibited intensive growth and contained twelve phenolic acid derivatives, with rosmarinic acid predominating. The cotyledon-derived callus line displayed the highest growth index values and polyphenol content; this was exposed to different light-emitting diodes (LED) for improving biomass accumulation and secondary metabolite yield. Under LED treatments, all callus lines exhibited enhanced RA and total phenolic content compared to fluorescent light, with the highest levels observed for white (48.5-50.2 mg/g dry weight) and blue (51.4-53.9 mg/g dry weight) LEDs. The selected callus demonstrated strong antioxidant potential in vitro based on the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) tests. Our findings confirm that the S. atropatana callus system is suitable for enhanced rosmarinic acid production; the selected optimized culture provide high-quality plant-derived products.

One pot green synthesis of m-aminophenol-urea-glyoxal resin as pipette tip solid-phase extraction adsorbent for simultaneous determination of four plant hormones in watermelon juice.

Plant hormones (PHs) are a type of pesticide that can potentially affect human health. Therefore, their quantitative detection is particularly important. In this study, a green and economic method for the simultaneous extraction and determination of four PHs, namely thidiazuron, forchlorfenuron, 1-naphthylacetic acid, and 2-naphthoxyacetic acid, in watermelon juice was developed by using m-aminophenol-urea-glyoxal resin as the adsorbent for pipette tip solid phase extraction (PT-SPE) coupled with liquid chromatography. The resin was synthesized via a simple (one pot hydrothermal synthesis) and green (ethanol as the solvent and glyoxal as crosslinking agent) process. The synthesized resin possesses multiple functional groups (hydroxyl, amino, and imino, among others), high adsorption capacity, larger specific surface area than the urea-glyoxal resin and m-aminophenol-glyoxal resin, and can be regenerated easily. The PT-SPE device is simple, cheap, and easy to obtain, and the adsorbent dosage is only 5.0 mg. The proposed method has a wide linear detection range, high recovery, good precision, and high sensitivity, and satisfies the measurement requirements for detecting trace levels of PHs in fruits and vegetables.

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

Six coumarin-caged compounds of 1-naphthaleneacetic acid (NAA) comprising different substituents on the coumarin moiety were synthesized and evaluated for their photophysical and chemical properties as light-responsive controlled-release plant root stimulators. The 1H NMR and HPLC techniques were used to verify the release of NAA from the caged compounds. After irradiation at 365 nm, the caged compounds exhibited the fastest release rate at t1/2 of 6.7 days and the slowest release rate at t1/2 of 73.7 days. Caged compounds at high concentrations (10-5 and 10-6 M) significantly stimulate secondary root germination while free NAA at the same level is toxic and leads to inhibition of secondary root germination. The cytotoxicity of the caged compounds against fibroblasts and vero cells were evaluated, and the results suggested that, at 10-5-10-6 M, caged compounds exhibited no significant cytotoxicity to the cells. Thus, the caged compounds of NAA in this study could be of great benefit as efficient agrochemicals.

High frequency regeneration of plants via callus-mediated organogenesis from cotyledon and hypocotyl cultures in a multipurpose tropical tree (Neolamarkia Cadamba).

In this works, a simple, efficient and repeatable protocol was developed for in vitro regeneration via callus-mediated organogenesis of Neolamarkia Cadamba using cotyledonary petioles and hypocotyls. Effects of basal medium, plant growth regulators, the types and age of explant on the formation of adventitious buds/shoots were studied. Meanwhile, histological analysis for early ontogenic stages and genetic stability assessment by flow cytometry were investigated. Our investigation demonstrated that, compared with 6-benzyladenine (BA), N6-(2-isopentenyl) adenine (2-ip), Thidiazuron (TDZ) was the optimal cytokinin for buds/shoots induction on cotyledon and hypocotyl explants. Douglas-fir and sugar pine medium (DCR) supplemented with 22.7 µM TDZ and 0.27 µM α-naphthalene acetic acid (NAA) was most effective on bud induction, with the highest bud-induction rate and numbers of buds on cotyledon and hypocotyl explants. The available shoot per explant hit 35.2 when the induced callus sub-cultured to a medium without TDZ. It was found that TDZ could promote induction of the callus and the buds, however, continuous exposure beyond 4 weeks of supplemented high concentration (exceed 11.35 µM), TDZ was harmful to the proliferation and growth of buds/shoots. DCR appeared more efficiency than Murashige and Skoog medium (MS), Woody Plant medium (WPM), anther culture of cereal crops medium (N6) on bud induction. Age of cotyledon and hypocotyl explants in 20-day to 25-day was most beneficial to adventitious buds/shoots formation. Histological investigation confirmed that the buds originated from the wounded incisions of cotyledonary petiole and hypocotyl fragments, with callus formation. The regeneration plantlets were successfully acclimatized in greenhouse, yielded above 95% survival rate in field, exhibited normal morphology and growth characteristics. The analysis of flow cytometry on N. cadamba indicated no variation in the ploidy levels between the regenerated plantlets and the donor trees. The developed procedure can be used for mass production, germplasm exchange and transgenic studies to improve the resistance of the species via Agrobacterium-mediated.

Rapid Degradation of Caenorhabditis elegans Proteins at Single-Cell Resolution with a Synthetic Auxin.

As developmental biologists in the age of genome editing, we now have access to an ever-increasing array of tools to manipulate endogenous gene expression. The auxin-inducible degradation system allows for spatial and temporal control of protein degradation via a hormone-inducible Arabidopsis F-box protein, transport inhibitor response 1 (TIR1). In the presence of auxin, TIR1 serves as a substrate-recognition component of the E3 ubiquitin ligase complex SKP1-CUL1-F-box (SCF), ubiquitinating auxin-inducible degron (AID)-tagged proteins for proteasomal degradation. Here, we optimize the Caenorhabditis elegans AID system by utilizing 1-naphthaleneacetic acid (NAA), an indole-free synthetic analog of the natural auxin indole-3-acetic acid (IAA). We take advantage of the photostability of NAA to demonstrate via quantitative high-resolution microscopy that rapid degradation of target proteins can be detected in single cells within 30 min of exposure. Additionally, we show that NAA works robustly in both standard growth media and physiological buffer. We also demonstrate that K-NAA, the water-soluble, potassium salt of NAA, can be combined with microfluidics for targeted protein degradation in C. elegans larvae. We provide insight into how the AID system functions in C. elegans by determining that TIR1 depends on C. elegans SKR-1/2, CUL-1, and RBX-1 to degrade target proteins. Finally, we present highly penetrant defects from NAA-mediated degradation of the FTZ-F1 nuclear hormone receptor, NHR-25, during C. elegans uterine-vulval development. Together, this work improves our use and understanding of the AID system for dissecting gene function at the single-cell level during C. elegans development.

A supramolecular hydrogel for spatial-temporal release of auxin to promote plant root growth.

Short peptide-based hydrogels have attracted extensive research interests in drug delivery because of their responsive properties. So far, most drug molecules have been conjugated with short peptides via an amide bond, restricting the release of the native drug molecules. In this study, we demonstrated the effectiveness of an auxin-based hydrogelator linked by a hydrolysable ester bond. Hydrogel I, formed by the gelator (NAA-G'FFY) linked with an ester bond, was able to release 1-naphthaleneacetic acid (NAA), whereas hydrogel II, formed by the gelator without an ester bond (NAA-GFFY), was not. By mixing NAA-G'FFY with Fmoc-GFFY to form a two-component hydrogel, the spatial and temporal release of NAA was achieved, promoting on-site auxin responses including primary root elongation and lateral root formation in the model plant Arabidopsis thaliana. The strategy of using a hydrolysable ester bond to connect drug molecules and self-assembling peptides could lead to the development of supramolecular hydrogels with more controllable drug release profiles.

1-Naphthyl acetate: A chromogenic substrate for the detection of erythrocyte acetylcholinesterase activity.

Erythrocyte acetylcholinesterase (AChE) is a preferred biomarker for the detection of organophosphorus poisoning. Acetylthiocholine (ATCh) is the most popular substrate for the detection of AChE activity. However, oximolysis is a prominent feature with ATCh. In this context, we have searched alternative substrates for AChE using in silico tools for screening of a better substrate. The in silico approach was performed to understand the fitness and the Total Interaction Energy (TIE) of substrates for AChE. The alternative substrates for AChE were screened in terms of high Goldscore and favorable TIE in comparison to acetylcholine (ACh)-AChE complex and other relevant esterases. Among the screened substrates, 1-Naphthyl acetate (1-NA) exhibited the most favorable interaction with AChE in terms of highest TIE and corresponding high Goldscore. The Molecular Dynamic (MD) simulation of the 1-NA-AChE complex showed a stable complex formation over a period of 5 ns. The results obtained in the in silico studies were validated in vitro using pure erythrocyte AChE and hemolysate. We observed 1-NA to be a better alternative substrate for AChE than ATCh in terms of lower Km value. Its specificity appeared at least similar to ATCh. Therefore, we propose that 1-NA can be an attractive chromogenic substrate for the measurement of AChE activity, and it possess the potential to detect organophosphorus pesticide (OP) poisoning.

Crystal structure of phospholipase A2 in complex with 1-naphthaleneacetic acid.

Phospholipase A2 (PLA2 ) is one of the rate limiting enzymes involved in the production of arachidonic acid, a potent inflammatory mediator. PLA2 is widely distributed all over the animal kingdom. It is also seen in inflammatory exudation and venoms of different organisms. The studies demonstrated that PLA2 inhibitors have broad spectrum activities that they can either be used against inflammation or envenomation. In this study, the inhibitory activity of 1-napthaleneacetic acid (NAA) against porcine pancreatic PLA2 has been explained through isothermal titration calorimetry and enzyme kinetics studies. The atomic level of interactions of NAA with PLA2 was also studied using X-ray crystallography. Apart from these findings, the theoretical binding affinities and mode of interactions of two naphthalene-based NSAIDs such as naproxen (NAP) and nabumetone (NAB) were studied through molecular modeling. The studies proved that the selected ligands are binding at the doorway of the active site cleft and hindering the substrate entry to the active site. The study brings out a potential scaffold for the designing of broad spectrum PLA2 inhibitors which can be used for inflammation or envenomation. © 2018 IUBMB Life, 70(10):995-1001, 2018.

Exploring Orthogonal Hydrogen Bonding towards Designing Organic-Salt-Based Supramolecular Gelators: Synthesis, Structures, and Anticancer Properties.

A series of primary ammonium monocarboxylate (PAM) salts derived from ß-alanine derivatives of pyrene and naphthalene acetic acid, along with the parent acids, were explored to probe the plausible role of orthogonal hydrogen bonding resulting from amide⋅⋅⋅amide and PAM synthons on gelation. Single-crystal X-ray diffraction (SXRD) studies were performed on two parent acids and five PAM salts in the series. The data revealed that orthogonal hydrogen bonding played an important role in gelation. Structure-property correlation based on SXRD and powder X-ray diffraction data also supported the working hypothesis upon which these gelators were designed. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell migration assay on a highly aggressive human breast cancer cell line, MDA-MB-231, revealed that one of the PAM salts in the series, namely, PAA.B2, displayed anticancer properties, and internalization of the gelator salt in the same cell line was confirmed by cell imaging.

Optimized Direct Organogenesis from Shoot Tip Explants of Date Palm.

In vitro propagation is an available alternative to produce uniform and good-quality planting material to establish large-scale date palm cultivation in a short time. This study was carried out to achieve organogenesis and multiplication directly from shoot tips without callus formation, thus avoiding any possibility of undesirable genetic variability among the regenerated plants. The shoot tips explants are cultured on Murashige and Skoog (MS) medium supplemented with 1 mg/L naphthaleneacetic acid (NAA), 1 mg/L naphthoxyacetic acid (NOA), 2.5 mg/L benzyladenine (BA), and 2.5 mg/L isopentenyladenine (2iP). Numerous adventitious buds appeared from the shoot tip explants in darkness after six subcultures at 4-week intervals. Vegetative buds pass through three stages: initiation bud formation, vegetative bud differentiation, and shoot bud proliferation. Shoots are transferred onto medium containing low concentrations of growth regulators for shoot multiplication. The organogenesis protocol described herein consists of six steps: initiation of meristematic buds, multiplication, elongation, rooting, pre-acclimatization, and finally plant acclimatization.

Histological Evidence of Indirect Somatic Embryogenesis from Immature Female Date Palm Inflorescences.

Rapid production of somatic embryogenesis and date palm regeneration is achieved by culturing immature female inflorescence explants. Inflorescence explants are soft, creamy in color, average 6-7 cm in length, and cultured on Murashige and Skoog (MS) medium containing 1 mg/L thidiazuron (TDZ). Callus induction occurs after 4-5 weeks of culture on the callus induction medium. Subsequently, callus develops embryogenic calli on MS medium supplemented with 0.1 mg/L naphthalene acetic acid (NAA). Histological samples were collected successively at the culturing time and during morphogenetic changes throughout the developmental stages of somatic embryos. Initiation of callus and different successive developmental stages for somatic embryos including two-celled, four-celled, globular, bipolar, and fully developed cotyledonary somatic embryos were observed. Mature somatic embryos develop within 10-12 weeks after culture establishment.

An enantiomer-based virtual screening approach: Discovery of chiral organophosphates as acetyl cholinesterase inhibitors.

Chiral organophosphates (OPs) have been used widely around the world, very little is known about binding mechanisms with biological macromolecules. An in-depth understanding of the stereo selectivity of human AChE and discovering bioactive enantiomers of OPs can decrease health risks of these chiral chemicals. In the present study, a flexible molecular docking approach was conducted to investigate different binding modes of twelve phosphorus enantiomers. A pharmacophore model was then developed on basis of the bioactive conformations of these compounds. After virtual screening, twenty-four potential bioactive compounds were found, of which three compounds (Ethyl p-nitrophenyl phenylphosphonate (EPN), 1-naphthaleneacetic anhydride and N,4-dimethyl-N-phenyl-benzenesulfonamide) were tested by use of different in vitro assays. S-isomer of EPN was also found to exhibit greater inhibitory activity towards human AChE than the corresponding R-isomer. These findings affirm that stereochemistry plays a crucial role in virtual screening, and provide a new insight into designing safer organ phosphorus pesticides on human health.

The impact of auxins used in assisted phytoextraction of metals from the contaminated environment on the alterations caused by lead(II) ions in the organization of model lipid membranes.

Auxins are successfully used to improve phytoextraction efficiency of metal ions from the contaminated environment, however, the mechanism of their activity in this field is not explained. Auxins are known to exert various biochemical alterations in the plant membranes and cells, but their activity involves also direct interactions with lipids leading to changes in membrane organization. Following the suggestion that the auxins-induced modifications in membrane properties alleviate toxic effect of metal ions in this paper we have undertaken the comparative studies on the effect of metal ions and metal ions/auxins mixtures on model membrane systems. The experiments were done on lipid monolayers differing in their composition spread on water subphase and on Pb(2+), Indole-3-acetic acid (IAA), 1-Naphthaleneacetic acid (NAA) and Pb(2+)/IAA and Pb(2+)/NAA water solutions. The analysis of the collected data suggests that metal ions and auxins can change fluidity of the lipid systems and weaken the interactions between monolayer components. This manifested in the increase of the mean area per molecule and the excess area per molecule values for the films on Pb(2+), auxins as well as Pb(2+)/auxin solutions as compared to the values on pure water subphase. However, the presence of auxin in the mixture with lead(II) ions makes the alterations induced by sole metal ions weaker. This effect was more pronounced for the membranes of a higher packing. Thus it was proposed that auxins may enhance phytoextraction of metal ions by weakening their destabilizing effect on membrane.

Free radical scavenging activity in in vitro-derived tissues of Eruca sativa.

Feasible regeneration protocol for economically important plant Eruca sativa was established and 1, 1-diphenyl-2-picrylhydrazyl scavenging activity of regenerated tissues was evaluated and compared with plant material collected from the wild. Leaf portions inoculated onto Murashige and Skoog (MS) medium responded to all plant growth regulators exploited. Optimum callus production was achieved on a combination of 2.0 mg l(-1) 6-benzyladenine (BA) + 1.0 mg l(-1) α-naphthalene acetic acid (NAA) and the lowest response was recorded for 0.5 mg l(-1) gibberellic acid (GA3) + 1.0 mg l(-1) NAA. The callus was subcultured on similar composition/concentrations of plant growth regulators after 4 weeks of culture time. A 5.0 mg l(-1) 6-BA + 1.0 mg l(-1) NAA produced optimum percentage shoot organogenesis after 4 weeks of subculturing. However, optimum number of shoots per explant was recorded for moderate concentrations (1.0 and 2.0 mg l(-1)) of kinetin. Incorporation of NAA into MS medium-containing GA3 also produced a feasible number of shoots/explant. Similar mean shoot length was recorded for 2.0 mg l(-1) kinetin + 1.0 mg l(-1) NAA and optimum concentrations (2.0, 5.0, and 10.0 mg l(-1)) of GA3 + 1.0 mg l(-1) NAA. In vitro generated shoots were shifted to MS medium augmented with indole acetic acid (IAA) for rooting after 4 weeks of subculturing. Moderate concentrations (5.0 mg l(-1)) of IAA produced feasible rooting. Investigation of radical scavenging activity showed that callus possesses higher levels of radical scavengers than other plant tissues tested. Phenolics and glucosides are reported to be active components of Eruca sativa phytochemistry.

Enhanced skin permeation of 6-methoxy-2-naphthylacetic acid by salt formation.

The aim of this work was to prepare salts of 6-methoxy-2-naphthylacetic acid (6-MNA) to improve its physicochemical properties for percutaneous application. 6-MNA, an active metabolite of non-steroidal anti-inflammatory drug nabumetone has long half life and has the tendency to penetrate well into synovial fluid. The physicochemical properties of 6-MNA salts were investigated by solubility measurements, differential scanning calorimetry (DSC) and infrared (IR). The DSC thermograms and Fourier transform infrared (FT-IR) spectra indicated that 6-MNA formed salts with organic and alkali metal bases. Among the series, salts formed with amine bases (ethanolamine, diethanolamine, triethanolamine and diethylamine) had lower melting points while alkali metal salt (sodium) had higher melting point than 6-MNA. The salts had higher solubilities than 6-MNA as determined in phosphate buffer at pH 5.0 and 7.4. There is no significant difference in partition coefficient (log P) values between salts and 6-MNA at pH 5.0 but, at pH 7.4, the log P values for the salts increased by 4-10 times as compared to 6-MNA. In vitro permeation studies showed that all the salts increased the flux in comparision to 6-MNA, and the ethanolamine salt (1b) was found to be having 7.7 and 9.4 times higher permeability as compared to 6-MNA at pH 5.0 and 7.4, respectively.

Molecular dynamics simulations of the auxin-binding protein 1 in complex with indole-3-acetic acid and naphthalen-1-acetic acid.

Auxin-binding protein 1 (ABP1) is suggested to be an auxin receptor which plays an important role in several processes in green plants. Maize ABP1 was simulated with the natural auxin indole-3-acetic acid (IAA) and the synthetic analog naphthalen-1-acetic acid (NAA), to elucidate the role of the KDEL sequence and the helix at the C-terminus. The KDEL sequence weakens the intermolecular interactions between the monomers but stabilizes the C-terminal helix. Conformational changes at the C-terminus occur within the KDEL sequence and are influenced by the binding of the simulated ligands. This observation helps to explain experimental findings on ABP1 interactions with antibodies that are modulated by the presence of auxin, and supports the hypothesis that ABP1 acts as an auxin receptor. Stable hydrogen bonds between the monomers are formed between Glu40 and Glu62, Arg10 and Thr97, Lys39, and Glu62 in all simulations. The amino acids Ile22, Leu25, Trp44, Pro55, Ile130, and Phe149 are located in the binding pocket and are involved in hydrophobic interactions with the ring system of the ligand. Trp151 is stably involved in a face to end interaction with the ligand. The calculated free energy of binding using the linear interaction energy approach showed a higher binding affinity for NAA as compared to IAA. Our simulations confirm the asymmetric behavior of the two monomers, the stronger interaction of NAA than IAA and offers insight into the possible mechanism of ABP1 as an auxin receptor.

Natural vs synthetic auxin: studies on the interactions between plant hormones and biological membrane lipids.

Analysis of the interactions between two representatives of plant hormones: synthetic (1-naphthaleneacetic acid, NAA) as well as natural (indole-3-acetic acid, IAA) and phospholipids occurring in biological membrane of both plant and animal cells was the subject of present studies. The aim of undertaken experiments was to elucidate the problem of direct influence of these plant growth regulators on phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) in monolayers at the air/water solution interface. The studied phospholipids differ not only as regards the structure of polar head-groups but also in the length of hydrophobic chains as well as their saturation degree. These differences result also in the main properties and functions of these phospholipids in biomembranes. The analysis of the results was based on the characteristics of the surface pressure (π)--area (A) isotherms registered for monolayers spread on the subphase containing plant hormone and as a reference on the surface of pure water. Moreover, as a complementary technique, Brewster angle microscopy was applied for the direct visualization of the investigated surface films. The obtained results revealed that auxins effectively influence phospholipids monolayers, regardless of the lipid structure, at the concentration of 10(-4)M. It was found that for this concentration, the influence of auxins was visibly larger in the case of PCs as compared to PEs. On the other hand, in the case of auxins solution of ≤ 10(-5)M, the observed trend was opposite. Generally, our studies showed that the natural plant hormone (IAA) interacts with the investigated lipid monolayers stronger than its synthetic derivative (NAA). The reason of these differences connects with the steric properties of both auxins; namely, the naphthalene ring of NAA molecule occupies larger space than the indole system of IAA. Therefore molecules of the latter compound penetrate easier into the region of phospholipids׳ polar head-groups. Moreover, the NH group of the indole moiety is capable of hydrogen bond formation with the acceptor groups in the polar fragment of lipid molecules. We proved also that among the investigated phospholipids, the highest susceptibility toward auxin influence show these lipids, for which during compression, surface film increases the degree of condensation.

Heterogeneous photocatalytic degradation of pesticides using decatungstate intercalated macroporous layered double hydroxides.

Decatungstate W10O32(4-) was efficiently intercalated between the layers of three-dimensionally ordered macroporous Mg2Al-layered double hydroxide. The structural and textural properties of as-prepared intercalated compound were characterized using different solid-state characterization techniques such as X-ray powder diffraction, FTIR and Raman spectroscopies and electronic microscopy. The photocatalytic properties of immobilized W10O32 (4-) within Mg2Al structure were investigated using 2-(1-naphthyl) acetamide (NAD) as a model of pesticide. The influence of different parameters such as amount of catalyst, pH and oxygen concentration were investigated. An optimal NAD degradation was obtained for a photocatalyst concentration of 60 mg l(-1). Under our experimental conditions, this heterogeneous photocatalyst induces photodegradation of 60 % of NAD after 17 h of irradiation at 365 nm and at pH 6.6. Interestingly, pesticide photodegradation leads to the mineralization of substrates to H2O and CO2 and the photocatalyst can be recycled and reused without any loss of activity over four cycles.

Auxin-induced hydrogen sulfide generation is involved in lateral root formation in tomato.

Similar to auxin, hydrogen sulfide (H2S), mainly produced by l-cysteine desulfhydrase (DES; EC 4.4.1.1) in plants, could induce lateral root formation. The objective of this study was to test whether H2S is also involved in auxin-induced lateral root development in tomato (Solanum lycopersicum L.) seedlings. We observed that auxin depletion-induced down-regulation of transcripts of SlDES1, decreased DES activity and endogenous H2S contents, and the inhibition of lateral root formation were rescued by sodium hydrosulfide (NaHS, an H2S donor). However, No additive effects were observed when naphthalene acetic acid (NAA) was co-treated with NaHS (lower than 10 mM) in the induction of lateral root formation. Subsequent work revealed that a treatment with NAA or NaHS could simultaneously induce transcripts of SlDES1, DES activity and endogenous H2S contents, and thereafter the stimulation of lateral root formation. It was further confirmed that H2S or HS(-), not the other sulfur-containing components derived from NaHS, was attributed to the stimulative action. The inhibition of lateral root formation and decreased of H2S metabolism caused by an H2S scavenger hypotaurine (HT) were reversed by NaHS, but not NAA. Molecular evidence revealed that both NaHS- or NAA-induced modulation of some cell cycle regulatory genes, including the up-regulation of SlCDKA;1, SlCYCA2;1, together with simultaneous down-regulation of SlKRP2, were differentially reversed by HT pretreatment. To summarize, above results clearly suggested that H2S might, at least partially, act as a downstream component of auxin signaling to trigger lateral root formation.

Molecular cocrystals of 5-(4-bromophenyl)-1,3,4-thiadiazol-2-amine: hydrogen bonding in the structures of the 1:1 adduct with 2-(naphthalen-2-yloxy)acetic acid and the salt with 3,5-dinitrobenzoic acid.

The crystal structures of the anhydrous products from the interaction of 5-(4-bromophenyl)-1,3,4-thiadiazol-2-amine with 2-(naphthalen-2-yloxy)acetic acid, viz. the 1:1 adduct C8H6BrN3S·C12H10O3, (I), and with 3,5-dinitrobenzoic acid, viz. the salt 2-amino-5-(4-bromophenyl)-1,2,4-thiadiazol-3-ium 3,5-dinitrobenzoate, C8H7BrN3S(+)·C7H3N2O6(-), (II), have been determined. In adduct (I), a heterodimer is formed through a cyclic hydrogen-bonding motif [graph set R2(2)(8)], involving carboxylic acid-heteroatom O-H···N and amine-carboxylic acid N-H···O interactions. The heterodimers are essentially planar, with a thiadiazole-to-naphthalene ring dihedral angle of 15.9 (2)° and an intramolecular thiadiazole-to-benzene ring angle of 4.7 (2)°. An amine-heteroatom N-H···N hydrogen bond between the heterodimers generates a one-dimensional chain structure extending down [001]. Also present are weak benzene-benzene and naphthalene-naphthalene π-π stacking interactions down the b axis [minimum ring-centroid separation = 3.936 (3) Å]. With salt (II), the cation-anion association is also through a cyclic R2(2)(8) motif but involving duplex N-H···O(carboxylate) hydrogen bonds, giving a heterodimer that is close to planar [dihedral angles between the thiadiazole ring and the two benzene rings = 5.00 (16) (intra) and 7.23 (15)° (inter)]. A secondary centrosymmetric cyclic RR4(2)(8) N-H···O(carboxylate) hydrogen-bonding association involving the second amino H atom generates a heterotetramer. Also present in the crystal structure are weak π-π interactions between thiadiazolium rings [minimum ring-centroid separation = 3.9466 (18) Å], as well as a short Br···O(nitro) interaction [3.314 (4) Å]. The two structures reported here now provide a total of three crystallographically characterized examples of cocrystalline products from the interaction of 5-(4-bromophenyl)-1,3,4-thiadiazol-2-amine with carboxylic acids, of which only one involves proton transfer.