Immobilization of Metal Nanoparticles to an Ultrathin Two-Dimensional Conjugated Metal-Organic Framework for Synergistic Electrocatalysis.

Metal-organic frameworks (MOFs) have been considered as promising hosts for immobilizing ultrafine metal nanoparticles (MNPs) due to their high surface area and porosity. However, electrochemical applications of such emerging composites are severely limited by the poor electrical conductivity and large size of the MOFs. Herein, we report the general synthesis of incorporating various MNPs into a conjugated MOF ultrathin nanosheet (Cu-TCPP UNS) matrix, which not only prevents agglomeration and restricts the growth of MNPs but also benefits the exposure of active sites and the transport of electrons. Specifically, the obtained PtCu@Cu-TCPP UNSs exhibited nearly two times higher mass activity for the methanol oxidation reaction (MOR) than the commercial Pt/C catalyst. Mechanistic studies reveal that the strong interaction between MNPs and Cu-TCPP promotes the oxidation of the CO intermediate. Moreover, the PtCu@Cu-TCPP UNSs can be employed as bifunctional electrocatalysts to couple MOR with the hydrogen evolution reaction for highly efficient hydrogen production.

UGT76F1 glycosylates an isomer of the C7-necic acid component of pyrrolizidine alkaloids in Arabidopsis thaliana.

Identification of unknown metabolites and their biosynthetic genes is an active research area in plant specialized metabolism. By following a gene-metabolite association from a genome-wide association study of Arabidopsis stem metabolites, we report a previously unknown metabolite, 2-hydroxy-2-(1-hydroxyethyl)pentanoic acid glucoside, and demonstrated that UGT76F1 is responsible for its production in Arabidopsis. The chemical structure of the glucoside was determined by a series of analyses, including tandem MS, acid and base hydrolysis, and NMR spectrometry. T-DNA knockout mutants of UGT76F1 are devoid of the glucoside but accumulate increased levels of the aglycone. 2-hydroxy-2-(1-hydroxyethyl)pentanoic acid is structurally related to the C7-necic acid component of lycopsamine-type pyrrolizidine alkaloids such as trachelantic acid and viridifloric acid. Feeding norvaline greatly enhances the accumulation of 2-hydroxy-2-(1-hydroxyethyl)pentanoic acid glucoside in wild-type but not the UGT76F1 knockout mutant plants, providing evidence for an orthologous C7-necic acid biosynthetic pathway in Arabidopsis despite the apparent lack of pyrrolizidine alkaloids.

Accelerated Proton Transfer in Asymmetric Active Units for Sustainable Acidic Oxygen Evolution Reaction.

The poor durability of Ru-based catalysts limits the practical application in proton exchange membrane water electrolysis (PEMWE). Here, we report that the asymmetric active units in Ru1-xMxO2 (M = Sb, In, and Sn) binary solid solution oxides are constructed by introducing acid-resistant p-block metal sites, breaking the activity and stability limitations of RuO2 in acidic oxygen evolution reaction (OER). Constructing highly asymmetric Ru-O-Sb units with a strong electron delocalization effect significantly shortens the spatial distance between Ru and Sb sites, improving the bonding strength of the overall structure. The unique two-electron redox couples at Sb sites in asymmetric active units trigger additional chemical steps at different OER stages, facilitating continuous proton transfer. The optimized Ru0.8Sb0.2O2 solid solution requires a superlow overpotential of 160 mV at 10 mA cm-2 and a record-breaking stability of 1100 h in an acidic electrolyte. Notably, the scale-prepared Ru0.8Sb0.2O2 achieves efficient PEMWE performance under industrial conditions. General mechanism analysis shows that the enhanced proton transport in the asymmetric Ru-O-M unit provides a new working pathway for acidic OER, breaking the scaling relationship without sacrificing stability.

Dynamic Phase Transformations of Prussian Blue Analogue Crystals in Hydrotherms.

Prussian blue analogue (PBA)/metal-organic frameworks (MOFs) are multifunctional precursors for the synthesis of metal/metal compounds, carbon, and their derived composites (P/MDCs) in chemical, medical, energy, and other applications. P/MDCs combine the advantages of both the high specific surface area of PBA/MOF and the electronic conductivity of metal compound/carbon. Although the calcination under different atmospheres has been extensively studied, the transformation mechanism of PBA/MOF under hydrothermal conditions remains unclear. The qualitative preparation of P/MDCs in hydrothermal conditions remains a challenge. Here, we select PBA to construct a machine-learning model and measure its hydrothermal phase diagram. The architecture-activity relationship of substances among nine parameters was analyzed for the hydrothermal phase transformation of PBA. Excitingly, we established a universal qualitative model to accurately fabricate 31 PBA derivates. Additionally, we performed three-dimensional reconstructed transmission electron microscopy, X-ray absorption fine structure spectroscopy, ultraviolet photoelectron spectroscopy, in situ X-ray powder diffraction, and theoretical calculation to analyze the advantages of hydrothermal derivatives in the oxygen evolution reaction and clarify their reaction mechanisms. We uncover the unified principles of the hydrothermal phase transformation of PBA, and we expect to guide the design for a wide range of composites.

Electron-Spin Regulation Driving Heterointerface Electron Distribution and Phase Transition toward Ultrafast and Durable Sodium Storage.

Phase engineering is an effective strategy for modulating the electronic structure and electron transfer mobility of cobalt selenide (CoSe2) with remarkable sodium storage. Nevertheless, it remains challenging to improve fast-charging and cycling performance. Herein, a heterointerface coupling induces phase transformation from cubic CoSe2 to orthorhombic CoSe2 accompanied by the formation of MoSe2 to construct a CoSe2/MoSe2 heterostructure decorated with N-doped carbon layer on a 3D graphene foam (CoSe2/MoSe2@NC/GF). The incorporated Mo cations in the bridged o-CoSe2/MoSe2 not only act an electron donor to regulate charge-spin configurations with more active electronic states but also trigger the upshift of d/p band centers and a decreased ∆d-p band center gap, which greatly enhances ion adsorption capability and lowers the ion diffusion barrier. As expected, the CoSe2/MoSe2@NC/GF anode demonstrates a high-rate capability of 447 mAh g-1 at 2 A g-1 and an excellent cyclability of 298 mAh g-1 at 1 A g-1 over 1000 cycles. The work deepens the understanding of the elaborate construction of heterostructured electrodes for high-performance SIBs.

Enhancing Zinc Electrode Stability Through Pre-Desolvation and Accelerated Charge Transfer via a Polyimide Interface for Zinc-Ion Batteries.

Aqueous zinc-based energy storage devices possess superior safety, cost-effectiveness, and high energy density; however, dendritic growth and side reactions on the zinc electrode curtail their widespread applications. In this study, these issues are mitigated by introducing a polyimide (PI) nanofabric interfacial layer onto the zinc substrate. Simulations reveal that the PI nanofabric promotes a pre-desolvation process, effectively desolvating hydrated zinc ions from Zn(H2O)6 2+ to Zn(H2O)4 2+ before approaching the zinc surface. The exposed zinc ion in Zn(H2O)4 2+ provides an accelerated charge transfer process and reduces the activation energy for zinc deposition from 40 to 21 kJ mol-1. The PI nanofabric also acts as a protective barrier, reducing side reactions at the electrode. As a result, the PI-Zn symmetric cell exhibits remarkable cycling stability over 1200 h, maintaining a dendrite-free morphology and minimal byproduct formation. Moreover, the cell exhibits high stability and low voltage hysteresis even under high current densities (20 mA cm-2, 10 mAh cm-2) thanks to the 3D porous structure of PI nanofabric. When integrated into full cells, the PI-Zn||AC hybrid zinc-ion capacitor and PI-Zn||MnVOH@SWCNT zinc-ion battery achieve impressive lifespans of 15000 and 600 cycles with outstanding capacitance retention. This approach paves a novel avenue for high-performance zinc metal electrodes.

Electronic and Atomic Structural Properties Associated with Enhanced Photodegradation Activity in Mo-Doped TiO2 Nanoparticles.

The efficacy and structural evolution of Mo-doped titania nanoparticles (MTNPs) as advanced photocatalysts for degrading methyl blue (MB) are investigated by X-ray absorption spectroscopy (XAS). The 3 wt % MTNP, characterized by uniform size and anatase structure, exhibits higher efficiency. The spectral analyses unveiled structural variations in the TiO6 octahedral structure and revealed an active site of the distorted square pyramidal structure symmetry (C4v). The in situ XAS spectra illustrate that MTNPs, particularly at 3 wt % doping, effectively enhanced the hole carriers in Ti 3d orbitals with a charge transfer to Mo 4d orbitals and impeded electron-hole pair merging, significantly enhancing the photodegradation under light illumination. This study deepens our understanding of the crucial role of Mo doping in optimizing TiO2 nanoparticle performance for efficient environmental remediation, showcasing the potential of MTNPs as sustainable photocatalytic materials.

Encapsulation of Sn Sub-Nanoclusters in Multichannel Carbon Matrix for High-Performance Potassium-Ion Batteries.

Sub-nanoclusters with ultra-small particle sizes are particularly significant to create advanced energy storage materials. Herein, Sn sub-nanoclusters encapsulated in nitrogen-doped multichannel carbon matrix (denoted as Sn-SCs@MCNF) are designed by a facile and controllable route as flexible anode for high-performance potassium ion batteries (PIBs). The uniformly dispersed Sn sub-nanoclusters in multichannel carbon matrix can be precisely identified, which ensure us to clarify the size influence on the electrochemical performance. The sub-nanoscale effect of Sn-SCs@MCNF restrains electrode pulverization and enhances the K+ diffusion kinetics, leading to the superior cycling stability and rate performance. As freestanding anode in PIBs, Sn-SCs@MCNF manifests superior K+ storage properties, such as exceptional cycling stability ( around 331 mAh g-1 after 150 cycles at 100 mA g-1) and rate capability. Especially, the Sn-SCs@MCNF||KFe[Fe(CN)6] full cell demonstrates impressive reversible capacity of around 167 mAh g-1 at 0.4 A g-1 even after 200 cycles. Theoretical calculations clarify that the ultrafine Sn sub-nanoclusters are beneficial for electron transfer and contribute to the lower energy barriers of the intermediates, thereby resulting in promising electrochemical performance. Comprehensive investigation for the intrinsic K+ storage process of Sn-SCs@MCNF is revealed by in situ analysis. This work provides vital guidance to design sub-nanoscale functional materials for high-performance energy-storage devices.

Manipulating the Microenvironment of Single Atoms by Switching Support Crystallinity for Industrial Hydrogen Evolution.

Modulating the microenvironment of single-atom catalysts (SACs) is critical to optimizing catalytic activity. Herein, we innovatively propose a strategy to improve the local reaction environment of Ru single atoms by precisely switching the crystallinity of the support from high crystalline and low crystalline, which significantly improves the hydrogen evolution reaction (HER) activity. The Ru single-atom catalyst anchored on low-crystalline nickel hydroxide (Ru-LC-Ni(OH)2 ) reconstructs the distribution balance of the interfacial ions due to the activation effect of metal dangling bonds on the support. Single-site Ru with a low oxidation state induces the aggregation of hydronium ions (H3 O+ ), leading to the formation of a local acidic microenvironment in alkaline media, breaking the pH-dependent HER activity. As a comparison, the Ru single-atom catalyst anchored on high-crystalline nickel hydroxide (Ru-HC-Ni(OH)2 ) exhibits a sluggish Volmer step and a conventional local reaction environment. As expected, Ru-LC-Ni(OH)2 requires low overpotentials of 9 and 136 mV at 10 and 1000 mA cm-2 in alkaline conditions and operates stably at 500 mA cm-2 for 500 h in an alkaline seawater anion exchange membrane (AEM) electrolyzer. This study provides a new perspective for constructing highly active single-atom electrocatalysts.

Polarized Ultrathin BN Induced Dynamic Electron Interactions for Enhancing Acidic Oxygen Evolution.

Developing ruthenium-based heterogeneous catalysts with an efficient and stable interface is essential for enhanced acidic oxygen evolution reaction (OER). Herein, we report a defect-rich ultrathin boron nitride nanosheet support with relatively independent electron donor and acceptor sites, which serves as an electron reservoir and receiving station for RuO2, realizing the rapid supply and reception of electrons. Through precisely controlling the reaction interface, a low OER overpotential of only 180 mV (at 10 mA cm-2) and long-term operational stability (350 h) are achieved, suggesting potential practical applications. In situ characterization and theoretical calculations have validated the existence of a localized electronic recycling between RuO2 and ultrathin BN nanosheets (BNNS). The electron-rich Ru sites accelerate the adsorption of water molecules and the dissociation of intermediates, while the interconnection between the O-terminal and B-terminal edge establishes electronic back-donation, effectively suppressing the over-oxidation of lattice oxygen. This study provides a new perspective for constructing a stable and highly active catalytic interface.

Spiral-Concave Prussian Blue Crystals with Rich Steps: Growth Mechanism and Coordination Regulation.

Investigating the formation and transformation mechanisms of spiral-concave crystals holds significant potential for advancing innovative material design and comprehension. We examined the kinetics-controlled nucleation and growth mechanisms of Prussian Blue crystals with spiral concave structures, and constructed a detailed crystal growth phase diagram. The spiral-concave hexacyanoferrate (SC-HCF) crystals, characterized by high-density surface steps and a low stress-strain architecture, exhibit enhanced activity due to their facile interaction with reactants. Notably, the coordination environment of SC-HCF can be precisely modulated by the introduction of diverse metals. Utilizing X-ray absorption fine structure spectroscopy and in situ ultraviolet-visible spectroscopy, we elucidated the formation mechanism of SC-HCF to Co-HCF facilitated by oriented adsorption-ion exchange (OA-IE) process. Both experimental data, and density functional theory confirm that Co-HCF possesses an optimized energy band structure, capable of adjusting the local electronic environment and enhancing the performance of the oxygen evolution reaction. This work not only elucidates the formation mechanism and coordination regulation for rich steps HCF, but also offers a novel perspective for constructing nanocrystals with intricate spiral-concave structures.

Transferability of Alzheimer's disease progression subtypes to an independent population cohort.

In the past, methods to subtype or biotype patients using brain imaging data have been developed. However, it is unclear whether and how these trained machine learning models can be successfully applied to population cohorts to study the genetic and lifestyle factors underpinning these subtypes. This work, using the Subtype and Stage Inference (SuStaIn) algorithm, examines the generalisability of data-driven Alzheimer's disease (AD) progression models. We first compared SuStaIn models trained separately on Alzheimer's disease neuroimaging initiative (ADNI) data and an AD-at-risk population constructed from the UK Biobank dataset. We further applied data harmonization techniques to remove cohort effects. Next, we built SuStaIn models on the harmonized datasets, which were then used to subtype and stage subjects in the other harmonized dataset. The first key finding is that three consistent atrophy subtypes were found in both datasets, which match the previously identified subtype progression patterns in AD: 'typical', 'cortical' and 'subcortical'. Next, the subtype agreement was further supported by high consistency in individuals' subtypes and stage assignment based on the different models: more than 92% of the subjects, with reliable subtype assignment in both ADNI and UK Biobank dataset, were assigned to an identical subtype under the model built on the different datasets. The successful transferability of AD atrophy progression subtypes across cohorts capturing different phases of disease development enabled further investigations of associations between AD atrophy subtypes and risk factors. Our study showed that (1) the average age is highest in the typical subtype and lowest in the subcortical subtype; (2) the typical subtype is associated with statistically more-AD-like cerebrospinal fluid biomarkers values in comparison to the other two subtypes; and (3) in comparison to the subcortical subtype, the cortical subtype subjects are more likely to associate with prescription of cholesterol and high blood pressure medications. In summary, we presented cross-cohort consistent recovery of AD atrophy subtypes, showing how the same subtypes arise even in cohorts capturing substantially different disease phases. Our study opened opportunities for future detailed investigations of atrophy subtypes with a broad range of early risk factors, which will potentially lead to a better understanding of the disease aetiology and the role of lifestyle and behaviour on AD.

Switching the Oxygen Evolution Mechanism on Atomically Dispersed Ru for Enhanced Acidic Reaction Kinetics.

Designing stable single-atom electrocatalysts with lower energy barriers is urgent for the acidic oxygen evolution reaction. In particular, the atomic catalysts are highly dependent on the kinetically sluggish acid-base mechanism, limiting the reaction paths of intermediates. Herein, we successfully manipulate the steric localization of Ru single atoms at the Co3O4 surface to improve acidic oxygen evolution by precise control of the anchor sites. The delicate structure design can switch the reaction mechanism from the lattice oxygen mechanism (LOM) to the optimized adsorbate evolution mechanism (AEM). In particular, Ru atoms embedded into cation vacancies reveal an optimized mechanism that activates the proton donor-acceptor function (PDAM), demonstrating a new single-atom catalytic pathway to circumvent the classic scaling relationship. Steric interactions with intermediates at the anchored Ru-O-Co interface played a primary role in optimizing the intermediates' conformation and reducing the energy barrier. As a comparison, Ru atoms confined to the surface sites exhibit a lattice oxygen mechanism for the oxygen evolution process. As a result, the delicate atom control of the spatial position presents a 100-fold increase in mass activity from 36.96 A gRu(ads)-1 to 4012.11 A gRu(anc)-1 at 1.50 V. These findings offer new insights into the precise control of single-atom catalytic behavior.

Dynamic Electronic and Ionic Transport Actuated by Cobalt-Doped MoSe2 /rGO for Superior Potassium-Ion Batteries.

Molybdenum selenium (MoSe2 ) has tremendous potential in potassium-ion batteries (PIBs) due to its large interlayer distance, favorable bandgap, and high theoretical specific capacity. However, the poor conductivity and large K+ insertion/extraction in MoSe2 inevitably leads to sluggish reaction kinetics and poor structural stability. Herein, Coinduced engineering is employed to illuminate high-conductivity electron pathway and mobile ion diffusion of MoSe2 nanosheets anchored on reduced graphene oxide substrate (Co-MoSe2 /rGO). Benefiting from the activated electronic conductivity and ion diffusion kinetics, and an expanded interlayer spacing resulting from Co doping, combined with the interface coupling with highly conductive reduced graphene oxide (rGO) substrate through Mo-C bonding, the Co-MoSe2 /rGO anode demonstrates remarkable reversible capacity, superior rate capability, and stable long-term cyclability for potassium storage, as well as superior energy density and high power density for potassium-ion capacitors. Systematic performance measurement, dynamic analysis, in-situ/ex-situ measurements, and density functional theory (DFT) calculations elucidate the performance-enhancing mechanism of Co-MoSe2 /rGO in view of the electronic and ionic transport kinetics. This work offers deep atomic insights into the fundamental factors of electrodes for potassium-ion batteries/capacitors with superior electrochemical performance.

Activity-Stability Balance: The Role of Electron Supply Effect of Support in Acidic Oxygen Evolution.

Developing efficient and durable electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) electrolyzers represents a significant challenge. Herein, the cobalt-ruthenium oxide nano-heterostructures are successfully synthesized on carbon cloth (CoOx /RuOx -CC) for acidic OER through a simple and fast solution combustion strategy. The rapid oxidation process endows CoOx /RuOx -CC with abundant interfacial sites and defect structures, which enhances the number of active sites and the charge transfer at the electrolyte-catalyst interface, promoting the OER kinetics. Moreover, the electron supply effect of the CoOx support allows electrons to transfer from Co to Ru sites during the OER process, which is beneficial to alleviate the ion leaching and over-oxidation of Ru sites, improving the catalyst activity and stability. As a self-supported electrocatalyst, CoOx /RuOx -CC displays an ultralow overpotential of 180 mV at 10 mA cm-2 for OER. Notably, the PEM electrolyzer using CoOx /RuOx -CC as the anode can be operated at 100 mA cm-2 stably for 100 h. Mechanistic analysis shows that the strong catalyst-support interaction is beneficial to redistribute the electronic structure of RuO bond to weaken its covalency, thereby optimizing the binding energy of OER intermediates and lowering the reaction energy barrier.

Stabilizing Low-Valence Single Atoms by Constructing Metalloid Tungsten Carbide Supports for Efficient Hydrogen Oxidation and Evolution.

Designing novel single-atom catalysts (SACs) supports to modulate the electronic structure is crucial to optimize the catalytic activity, but rather challenging. Herein, a general strategy is proposed to utilize the metalloid properties of supports to trap and stabilize single-atoms with low-valence states. A series of single-atoms supported on the surface of tungsten carbide (M-WCx , M=Ru, Ir, Pd) are rationally developed through a facile pyrolysis method. Benefiting from the metalloid properties of WCx , the single-atoms exhibit weak coordination with surface W and C atoms, resulting in the formation of low-valence active centers similar to metals. The unique metal-metal interaction effectively stabilizes the low-valence single atoms on the WCx surface and improves the electronic orbital energy level distribution of the active sites. As expected, the representative Ru-WCx exhibits superior mass activities of 7.84 and 62.52 A mgRu -1 for the hydrogen oxidation and evolution reactions (HOR/HER), respectively. In-depth mechanistic analysis demonstrates that an ideal dual-sites cooperative mechanism achieves a suitable adsorption balance of Had and OHad , resulting in an energetically favorable Volmer step. This work offers new guidance for the precise construction of highly active SACs.

Brevibacillus dissolubilis sp. nov., Isolated from Fresh Water.

A Gram-positive-staining, strictly aerobic, motile, ellipsoidal endospore-forming bacterial strain, designated CHY01T, was isolated from the Chishui river in a section of Maotai Town, Guizhou Province, Southwest China. Strain CHY01T was found to grow optimally at pH 8.0 and 28 °C. The 16S rRNA gene sequence analysis indicated that strain CHY01T belonged to the genus Brevibacillus and clustered with the type strain of Brevibacillus panacihumi, with which it exhibited 16S rRNA gene sequence similarity values of 97.8%. The predominant respiratory quinone was MK-7, and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The major fatty acids were C14:0, iso-C15:0, anteiso-C15:0, C16:0, C15:1iso-H and/or C13:0 3-OH, and C16:1ω7c and/or C16:1ω6c. Genome sequencing revealed a genome size of 6.1 Mbp and a G + C content of 50.6%. The results of physiological and biochemical tests allowed strain CHY01T to be distinguished genotypically and phenotypically from Brevibacillus species with validly published names. Pairwise determined whole-genome average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values suggested that strain CHY01T represents a new species, for which we propose the name Brevibacillus dissolubilis sp. nov. with the type strain CHY01T (= CGMCC 1.15916 T = KCTC 33863 T).

Association of China's two-child policy with changes in number of births and birth defects rate, 2008-2017.

BACKGROUND: In October 2015, China's one-child policy was universally replaced by a so-called two-child policy. This study investigated the association between the enactment of the new policy and changes in the number of births, and health-related birth outcomes. METHODS: We used difference-in-difference model to analyse the birth record data in Pudong New Area, Shanghai.The design is descriptive before-and-after comparative study. RESULTS: The data covered three policy periods: the one-child policy period (January 2008 to November 2014); the partial two-child policy period (December 2014 to June 2016); the universal two-child policy period (July 2016 to December 2017). There was an estimate of 7656 additional births during the 18 months of the implementation of the universal two-child policy. The trend of monthly percentage of births to mothers aged ≥35 increased by 0.24 percentage points (95% confidence interval 0.19 to 0.28, p < 0.001) during the same period. Being a baby boy, preterm birth, low birth weight, parents with lower educational attainment, and assisted delivery were associated with a higher risk of birth defects. CONCLUSIONS: The universal two-child policy was associated with an increase in the number of births and maternal age. Preterm birth, low birth weight, and assisted delivery were associated with a higher risk of birth defects, which suggested that these infants needed additional attention in the future.

Clusters Induced Electron Redistribution to Tune Oxygen Reduction Activity of Transition Metal Single-Atom for Metal-Air Batteries.

Oxygen reduction reaction (ORR) activity can be effectively tuned by modulating the electron configuration and optimizing the chemical bonds. Herein, a general strategy to optimize the activity of metal single-atoms is achieved by the decoration of metal clusters via a coating-pyrolysis-etching route. In this unique structure, the metal clusters are able to induce electron redistribution and modulate M-N species bond lengths. As a result, M-ACSA@NC exhibits superior ORR activity compared with the nanoparticle-decorated counterparts. The performance enhancement is attributed to the optimized intermediates desorption benefiting from the unique electronic configuration. Theoretical analysis reinforces the significant roles of metal clusters by correlating the ORR activity with cluster-induced charge transfer. As a proof-of-concept, various metal-air batteries assembled with Fe-ACSA@NC deliver remarkable power densities and capacities. This strategy is an effective and universal technique for electron modulation of M-N-C, which shows great potential in application of energy storage devices.

An importin-beta-like protein mediates lignin-modification-induced dwarfism in Arabidopsis.

Perturbation of lignin biosynthesis often results in severe growth and developmental defects in plants, which imposes practical limitations to genetic enhancement of lignocellulosic biomass for biofuel production. Currently, little information is known about the cellular and genetic mechanisms of this important phenomenon. Here we show that defects in both cell division and cell expansion underlie the dwarfism of an Arabidopsis lignin mutant ref8, and report the identification of a GROWTH INHIBITION RELIEVED 1 (GIR1) gene from a suppressor screen. GIR1 encodes an importin-beta-like protein required for the nuclear import of MYB4, a transcriptional repressor of phenylpropanoid metabolism. Disruption of GIR1 and MYB4 similarly alleviates the cellular defects and growth inhibition in ref8, suggesting that the growth rescue effect of gir1 is likely due to compromised MYB4 transport and function. Importantly, the phenylpropanoid perturbation is not alleviated in gir1 ref8 and myb4 ref8, suggesting that the function of MYB4 in growth inhibition of lignin-modified plants is likely to be distinct from its known role in transcriptional regulation of phenylpropanoid biosynthetic genes. This study also provides evidence that lignin-modification-induced dwarfism is not merely due to compromised water transport brought about by lignin deficiency, as gir1 has no effect on the growth inhibition of other lignin mutants that show the collapsed xylem phenotype.