Selective Alkane Hydroxylation in a Fluorous Solvent System Catalyzed by a Fluorocarbon-Soluble Transition-Metal Catalyst.

Hydroxylation of aliphatic hydrocarbons requires highly reactive oxidants, but their strength can lead to undesired oxidation of the initially formed alcohols and solvents, undermining the product selectivity. To address these problems, we developed a novel catalytic system using fluorocarbon solvents. A cobalt complex supported by the fluorinated ligand, N,N,N',N',N″-pentakis-[CF3(CF2)7(CH2)3]-diethylenetriamine (Rf-deta), acts as an efficient catalyst [turnover number (TON) = 1203, turnover frequency = 51 ± 1 min-1] for cyclohexane hydroxylation with the m-chloroperbenzoic acid oxidant, achieving high alcohol selectivity (96%). Overoxidation to form cyclohexanone is minimized due to the separation of cyclohexanol from the reaction phase, comprising perfluoromethylcyclohexane and α,α,α-trifluorotoluene. The catalyst hydroxylates primary carbons (5 examples) and exhibits significant reactivity toward the terminal C-H bond of normal hexane (TON = 13). This system extends to the hydroxylation of the gaseous substrate butane, yielding the corresponding alcohols.

Logical states for fault-tolerant quantum computation with propagating light.

To harness the potential of a quantum computer, quantum information must be protected against error by encoding it into a logical state that is suitable for quantum error correction. The Gottesman-Kitaev-Preskill (GKP) qubit is a promising candidate because the required multiqubit operations are readily available at optical frequency. To date, however, GKP qubits have been demonstrated only at mechanical and microwave frequencies. We realized a GKP state in propagating light at telecommunication wavelength and verified it through homodyne measurements without loss corrections. The generation is based on interference of cat states, followed by homodyne measurements. Our final states exhibit nonclassicality and non-Gaussianity, including the trident shape of faint instances of GKP states. Improvements toward brighter, multipeaked GKP qubits will be the basis for quantum computation with light.

Single-Shot Single-Mode Optical Two-Parameter Displacement Estimation beyond Classical Limit.

Uncertainty principle prohibits the precise measurement of both components of displacement parameters in phase space. We have theoretically shown that this limit can be beaten using single-photon states, in a single-shot and single-mode setting [F. Hanamura et al., Estimation of gaussian random displacement using non-gaussian states, Phys. Rev. A 104, 062601 (2021).PLRAAN2469-992610.1103/PhysRevA.104.062601]. In this Letter, we validate this by experimentally beating the classical limit. In optics, this is the first experiment to estimate both parameters of displacement using non-Gaussian states. This result is related to many important applications, such as quantum error correction.

Efficient Concatenated Bosonic Code for Additive Gaussian Noise.

Bosonic codes offer noise resilience for quantum information processing. Good performance often comes at a price of complex decoding schemes, limiting their practicality. Here, we propose using a Gottesman-Kitaev-Preskill code to detect and discard error-prone qubits, concatenated with a quantum parity code to handle the residual errors. Our method employs a simple linear-time decoder that nevertheless offers significant performance improvements over the standard decoder. Our Letter may have applications in a wide range of quantum computation and communication scenarios.

Non-Gaussian quantum state generation by multi-photon subtraction at the telecommunication wavelength.

In the field of continuous-variable quantum information processing, non-Gaussian states with negative values of the Wigner function are crucial for the development of a fault-tolerant universal quantum computer. While several non-Gaussian states have been generated experimentally, none have been created using ultrashort optical wave packets, which are necessary for high-speed quantum computation, in the telecommunication wavelength band where mature optical communication technology is available. In this paper, we present the generation of non-Gaussian states on wave packets with a short 8-ps duration in the 1545.32 nm telecommunication wavelength band using photon subtraction up to three photons. We used a low-loss, quasi-single spatial mode waveguide optical parametric amplifier, a superconducting transition edge sensor, and a phase-locked pulsed homodyne measurement system to observe negative values of the Wigner function without loss correction up to three-photon subtraction. These results can be extended to the generation of more complicated non-Gaussian states and are a key technology in the pursuit of high-speed optical quantum computation.

Desmethyl type germinone, a specific agonist for the HTL/KAI2 receptor, induces the Arabidopsis seed germination in a gibberellin-independent manner.

DWARF14 (D14) and HTL/KAI2 (KAI2) are paralogous receptors in the α/ß-hydrolase superfamily. D14 is the receptor for a class of plant hormones, strigolactones (SLs), and KAI2 is the receptor for the smoke-derived seed germination inducer, Karrikin (KAR), in Arabidopsis. Germinone (Ger) was previously reported as a KAI2 agonist with germination-inducing activity for thermo-inhibited Arabidopsis seed. However, Ger was not specific to KAI2, and could also bind to D14. It was reported that SL analogs with a desmethyl-type D-ring structure are specifically recognized by KAI2. On the basis of this observation, we synthesized a desmethyl-type germinone (dMGer). We found that dMGer is highly specific to KAI2. Moreover, dMGer induced Arabidopsis seed germination more effectively than did Ger. In addition, dMGer induced the seed germination of Arabidopsis in a manner independently of GA, a well-known germination inducer in plants.

Chemical inhibition of the auxin inactivation pathway uncovers the roles of metabolic turnover in auxin homeostasis.

The phytohormone auxin, indole-3-acetic acid (IAA), plays a prominent role in plant development. Auxin homeostasis is coordinately regulated by auxin synthesis, transport, and inactivation; however, the physiological contribution of auxin inactivation to auxin homeostasis has not been determined. The GH3 IAA-amino acid conjugating enzymes play a central role in auxin inactivation. Chemical inhibition of GH3 proteins in planta is challenging because the inhibition of these enzymes leads to IAA overaccumulation that rapidly induces GH3 expression. Here, we report the characterization of a potent GH3 inhibitor, kakeimide, that selectively targets IAA-conjugating GH3 proteins. Chemical knockdown of the auxin inactivation pathway demonstrates that auxin turnover is very rapid (about 10 min) and indicates that both auxin biosynthesis and inactivation dynamically regulate auxin homeostasis.

Efficient Backcasting Search for Optical Quantum State Synthesis.

Non-Gaussian states are essential for many optical quantum technologies. The so-called optical quantum state synthesizer (OQSS), consisting of Gaussian input states, linear optics, and photon-number resolving detectors, is a promising method for non-Gaussian state preparation. However, an inevitable and crucial problem is the complexity of the numerical simulation of the state preparation on a classical computer. This problem makes it very challenging to generate important non-Gaussian states required for advanced quantum information processing. Thus, an efficient method to design OQSS circuits is highly desirable. To circumvent the problem, we offer a scheme employing a backcasting approach, where the circuit of OQSS is divided into some sublayers, and we simulate the OQSS backwards from final to first layers. Moreover, our results show that the detected photon number by each detector is at most 2, which can significantly reduce the requirements for the photon-number resolving detector. By virtue of the potential for the preparation of a wide variety of non-Gaussian states, the proposed OQSS can be a key ingredient in general optical quantum information processing.

The main oxidative inactivation pathway of the plant hormone auxin.

Inactivation of the phytohormone auxin plays important roles in plant development, and several enzymes have been implicated in auxin inactivation. In this study, we show that the predominant natural auxin, indole-3-acetic acid (IAA), is mainly inactivated via the GH3-ILR1-DAO pathway. IAA is first converted to IAA-amino acid conjugates by GH3 IAA-amidosynthetases. The IAA-amino acid conjugates IAA-aspartate (IAA-Asp) and IAA-glutamate (IAA-Glu) are storage forms of IAA and can be converted back to IAA by ILR1/ILL amidohydrolases. We further show that DAO1 dioxygenase irreversibly oxidizes IAA-Asp and IAA-Glu into 2-oxindole-3-acetic acid-aspartate (oxIAA-Asp) and oxIAA-Glu, which are subsequently hydrolyzed by ILR1 to release inactive oxIAA. This work established a complete pathway for the oxidative inactivation of auxin and defines the roles played by auxin homeostasis in plant development.

On improving strigolactone mimics for induction of suicidal germination of the root parasitic plant Striga hermonthica.

Strigolactones (SLs) are plant hormones that regulate the branching of plants and seed germination stimulants of root parasitic plants. As root parasites are a great threat to agricultural production, the use of SL agonists could be anticipated to provide an efficient method for regulating root parasites as suicidal germination inducers. A series of phenoxyfuranone-type SL mimics, termed debranones, has been reported to show potent bioactivities, including reduction of the tiller number on rice, and stimulation of seed germination in the root parasite Striga hermonthica. To exert both activities, two substituents on the phenyl ring of the molecules were important but at least a substituent at the 2-position must be an electron-withdrawing group. However, little is known about the effect of the properties of the substituents at the 2-position on bioactivities. Here, we found that different substituents at the 2-position give different preferences for bioactivities. Halogenated debranones were more effective than the others and SL agonist GR24 for inhibiting rice tiller but far less effective in the induction of S. hermonthica germination. Meanwhile, nitrile and methyl derivatives clearly stimulated the germination of S. hermonthica seeds. Although their IC50 values were 100 times higher than that of GR24 in the receptor competitive binding assay, their physiological activities were approximately 1/10 of GR24. These differences could be due to their uptake in plants and/or their physicochemical stability under our experimental conditions. These findings could support the design of more potent and selective SL agonists that could contribute to solving big agricultural issues.

Ligand-receptor interactions in plant hormone signaling.

Small-molecule plant hormones principally control plant growth, development, differentiation, and environmental responses. Nine types of plant hormones are ubiquitous in angiosperms, and the molecular mechanisms of their hormone actions have been elucidated during the last two decades by genomic decoding of model plants with genetic mutants. In particular, the discovery of hormone receptors has greatly contributed to the understanding of signal transduction systems. The three-dimensional structure of the ligand-receptor complex has been determined for eight of the nine hormones by X-ray crystal structure analysis, and ligand perception mechanisms have been revealed at the atomic level. Collective research has revealed the molecular function of plant hormones that act as either molecular glue or an allosteric regulator for activation of receptors. In this review, we present an overview of the respective hormone signal transduction and describe the structural bases of ligand-receptor interactions.

Difference Between Day and Night Temperatures Affects Stem Elongation in Tomato (Solanum lycopersicum) Seedlings via Regulation of Gibberellin and Auxin Synthesis.

Temperature is a critical environmental factor governing plant growth and development. The difference between day temperature (DT) and night temperature (NT), abbreviated as DIF, influences plant architecture. Subjecting plants to artificial DIF treatments is an effective strategy in ornamental horticulture. For example, negative DIF (when DT - NT < 0) generally inhibits stem elongation, resulting in dwarf plants. However, the mechanisms underlying stem growth regulation by DIF remains to be completely elucidated. In this study, we aimed to analyze the growth, transcriptome, and phytohormone profiles of tomato (Solanum lycopersicum) seedlings grown under different DIF treatments. Under positive DIF (when DT - NT > 0), in contrast to the control temperature (25°C/20°C, DT/NT), high temperature (30°C/25°C) increased stem length and thickness, as well as the number of xylem vessels. Conversely, compared with the positive high temperature DIF treatment (30°C/25°C), under negative DIF treatment (25°C/30°C) stem elongation was inhibited, but stem thickness and the number of xylem vessels were not affected. The negative DIF treatment decreased the expression of gibberellin (GA)-, auxin-, and cell wall-related genes in the epicotyl, as well as the concentrations of GAs and indole-3-acetic acid (IAA). The expression of these genes and concentrations of these hormones increased under high temperature compared to those under the control temperature positive DIF. Our results suggest that stem length in tomato seedlings is controlled by changes in GA and IAA biosynthesis in response to varying day and night temperatures.

The auxin-inducible degron 2 technology provides sharp degradation control in yeast, mammalian cells, and mice.

Protein knockdown using the auxin-inducible degron (AID) technology is useful to study protein function in living cells because it induces rapid depletion, which makes it possible to observe an immediate phenotype. However, the current AID system has two major drawbacks: leaky degradation and the requirement for a high dose of auxin. These negative features make it difficult to control precisely the expression level of a protein of interest in living cells and to apply this method to mice. Here, we overcome these problems by taking advantage of a bump-and-hole approach to establish the AID version 2 (AID2) system. AID2, which employs an OsTIR1(F74G) mutant and a ligand, 5-Ph-IAA, shows no detectable leaky degradation, requires a 670-times lower ligand concentration, and achieves even quicker degradation than the conventional AID. We demonstrate successful generation of human cell mutants for genes that were previously difficult to deal with, and show that AID2 achieves rapid target depletion not only in yeast and mammalian cells, but also in mice.

UDP-glucosyltransferase UGT84B1 regulates the levels of indole-3-acetic acid and phenylacetic acid in Arabidopsis.

Auxin is a key plant growth regulator for diverse developmental processes in plants. Indole-3-acetic acid (IAA) is a primary plant auxin that regulates the formation of various organs. Plants also produce phenylacetic acid (PAA), another natural auxin, which occurs more abundantly than IAA in various plant species. Although it has been demonstrated that the two auxins have distinct transport characteristics, the metabolic pathways and physiological roles of PAA in plants remain unsolved. In this study, we investigated the role of Arabidopsis UDP-glucosyltransferase UGT84B1 in IAA and PAA metabolism. We demonstrated that UGT84B1, which converts IAA to IAA-glucoside (IAA-Glc), can also catalyze the conversion of PAA to PAA-glucoside (PAA-Glc), with a higher catalytic activity in vitro. Furthermore, we showed a significant increase in both the IAA and PAA levels in the ugt84b1 null mutants. However, no obvious developmental phenotypes were observed in the ugt84b1 mutants under laboratory growth conditions. Moreover, the overexpression of UGT84B1 resulted in auxin-deficient root phenotypes and changes in the IAA and PAA levels. Our results indicate that UGT84B1 plays an important role in IAA and PAA homeostasis in Arabidopsis.

Role of Arabidopsis INDOLE-3-ACETIC ACID CARBOXYL METHYLTRANSFERASE 1 in auxin metabolism.

The phytohormone auxin regulates a wide range of developmental processes in plants. Indole-3-acetic acid (IAA) is the main auxin that moves in a polar manner and forms concentration gradients, whereas phenylacetic acid (PAA), another natural auxin, does not exhibit polar movement. Although these auxins occur widely in plants, the differences between IAA and PAA metabolism remain largely unknown. In this study, we investigated the role of Arabidopsis IAA CARBOXYL METHYLTRANSFERASE 1 (IAMT1) in IAA and PAA metabolism. IAMT1 proteins expressed in Escherichia coli could convert both IAA and PAA to their respective methyl esters. Overexpression of IAMT1 caused severe auxin-deficient phenotypes and reduced the levels of IAA, but not PAA, in the root tips of Arabidopsis, suggesting that IAMT1 exclusively metabolizes IAA in vivo. We generated iamt1 null mutants via CRISPR/Cas9-mediated genome editing and found that the single knockout mutants had normal auxin levels and did not exhibit visibly altered phenotypes. These results suggest that other proteins, namely the IAMT1 homologs in the SABATH family of carboxyl methyltransferases, may also regulate IAA levels in Arabidopsis.

Synthetic agonist of HTL/KAI2 shows potent stimulating activity for Arabidopsis seed germination.

HTL/KAI2, a member of the α/ß-fold hydrolase superfamily, is known to be a receptor-like protein of lactone compounds and that triggers seed germination of Arabidopsis. However, the endogenous ligand and physiological roles of HTL/KAI2 have remained unclear. To understand the mechanism underlying seed germination involved in HTL/KAI2 signaling, it is necessary to identify the endogenous ligand of HTL/KAI2. To date, even a biosynthetic mutant of the ligand has not yet been isolated. Because exogenous agonistic chemicals can only be purchased in small amounts at high prices, the limited supply of those chemicals has hampered any large-scale experiments, such as mutant screening. Therefore, easily synthesized and scalable artificial agonist would remove the limitation of the chemical supply and contribute to the identification of the endogenous ligand of HTL/KAI2 and/or the biosynthetic mutants. In this study, we demonstrated that designed chemicals with a phenoxyfuranone scaffold potently stimulated seed germination via HTL/KAI2 in Arabidopsis. As a result of screening of these chemicals, we selected a representative compound with convincing selectivity. Here in, we provide a new promising synthetic agonist of HTL/KAI2.

Pinstatic Acid Promotes Auxin Transport by Inhibiting PIN Internalization.

Polar auxin transport plays a pivotal role in plant growth and development. PIN-FORMED (PIN) auxin efflux carriers regulate directional auxin movement by establishing local auxin maxima, minima, and gradients that drive multiple developmental processes and responses to environmental signals. Auxin has been proposed to modulate its own transport by regulating subcellular PIN trafficking via processes such as clathrin-mediated PIN endocytosis and constitutive recycling. Here, we further investigated the mechanisms by which auxin affects PIN trafficking by screening auxin analogs and identified pinstatic acid (PISA) as a positive modulator of polar auxin transport in Arabidopsis (Arabidopsis thaliana). PISA had an auxin-like effect on hypocotyl elongation and adventitious root formation via positive regulation of auxin transport. PISA did not activate SCFTIR1/AFB signaling and yet induced PIN accumulation at the cell surface by inhibiting PIN internalization from the plasma membrane. This work demonstrates PISA to be a promising chemical tool to dissect the regulatory mechanisms behind subcellular PIN trafficking and auxin transport.

New-Generation Chemical Tools for the Manipulation of Auxin Biosynthesis, Action, and Transport.

Auxin is the master regulator for almost every aspect of plant growth and development. Small molecule inhibitors, fluorescently labeled molecule, and hormone analogs on auxin biosynthesis, transport, and signaling, so-called auxin chemical tools, have been widely utilized to dissect physiological functions of gene families in auxin biosynthesis, transport, and signaling. Auxin chemical tools can manipulate specific auxin-regulated events at any developmental stage. Chemical tools can modulate the function of orthologs of target proteins and also can overcome the redundant function of large family gene controlling auxin-regulated response. On the other hand, chemical tool might induce the off-target effects at high concentration, if the chemical tool shows insufficient specificity on target proteins. This chapter describes a brief overview and practical application of the auxin chemical tools.

The Tetrazole Analogue of the Auxin Indole-3-acetic Acid Binds Preferentially to TIR1 and Not AFB5.

Indole-3-acetic acid (auxin) is considered one of the cardinal hormones in plant growth and development. It regulates a wide range of processes throughout the plant. Synthetic auxins exploit the auxin-signaling pathway and are valuable as herbicidal agrochemicals. Currently, despite a diversity of chemical scaffolds all synthetic auxins have a carboxylic acid as the active core group. By applying bio-isosteric replacement we discovered that indole-3-tetrazole was active by surface plasmon resonance spectrometry, showing that the tetrazole could initiate assembly of the Transport Inhibitor Resistant 1 (TIR1) auxin coreceptor complex. We then tested the tetrazole's efficacy in a range of whole plant physiological assays and in protoplast reporter assays, which all confirmed auxin activity, albeit rather weak. We then tested indole-3-tetrazole against the AFB5 homologue of TIR1, finding that binding was selective against TIR1, absent with AFB5. The kinetics of binding to TIR1 are contrasted to those for the herbicide picloram, which shows the opposite receptor preference, as it binds to AFB5 with far greater affinity than to TIR1. The basis of the preference of indole-3-tetrazole for TIR1 was revealed to be a single residue substitution using molecular docking, and assays using tir1 and afb5 mutant lines confirmed selectivity in vivo. Given the potential that a TIR1-selective auxin might have for unmasking receptor-specific actions, we followed a rational design, lead optimization campaign, and a set of chlorinated indole-3-tetrazoles was synthesized. Improved affinity for TIR1 and the preference for binding to TIR1 was maintained for 4- and 6-chloroindole-3-tetrazoles, coupled with improved efficacy in vivo. This work expands the range of auxin chemistry for the design of receptor-selective synthetic auxins.

Manipulation and Sensing of Auxin Metabolism, Transport and Signaling.

The plant hormone auxin is involved in virtually every aspect of plant growth and development. A chemical genetic approach has greatly contributed to the identification of important genes in auxin biosynthesis, transport and signaling. Molecular genetic technologies and structural information for auxin regulatory components have accelerated the identification and characterization of many novel small molecule modulators in auxin biology. These modulators have been widely utilized to dissect auxin responses. Here we provide an overview of the structure, primary target, in planta activity and application of small molecule modulators in auxin biology.