Flavonoids ubiquitously distribute to the terrestrial plants and chalcone isomerase (CHI)-catalyzed intramolecular and stereospecific cyclization of chalcones is a committed step in the production of ...flavonoids. However, so far the bona fide CHIs are found only in vascular plants, and their origin and evolution remains elusive.
We conducted transcriptomic and/or genomic sequence search, subsequent phylogenetic analysis, and detailed biochemical and genetic characterization to explore the potential existence of CHI proteins in the basal bryophyte liverwort species and the lycophyte Selaginella moellendorffii.
We found that both liverwort and Selaginella species possess canonical CHI-fold proteins that cluster with their corresponding higher plant counterparts. Among them, some members exhibited bona fide CHI activity, which catalyze stereospecific cyclization of both 6′-hydroxychalcone and 6′-deoxychalcone, yielding corresponding 5-hydroxy and 5-deoxyflavanones, resembling the typical type II CHIs currently known to be ‘specific’ for legume plants. Expressing those primitive bona fide CHIs in the Arabidopsis chi mutant restores the seed coat transparent testa phenotype and the accumulation of flavonoids.
These findings, in contrast to our current understanding of the evolution of enzymatic CHIs, suggest that emergence of the bona fide type II CHIs is an ancient evolution event that occurred before the divergence of liverwort lineages.
Good path planning technology of mobile robot can not only save a lot of time, but also reduce the wear and capital investment of mobile robot. Several methodologies have been proposed and reported ...in the literature for the path planning of mobile robot. Although these methodologies do not guarantee an optimal solution, they have been successfully applied in their works. The purpose of this paper is to review the modeling, optimization criteria and solution algorithms for the path planning of mobile robot. The survey shows GA (genetic algorithm), PSO (particle swarm optimization algorithm), APF (artificial potential field), and ACO (ant colony optimization algorithm) are the most used approaches to solve the path planning of mobile robot. Finally, future research is discussed which could provide reference for the path planning of mobile robot.
Abstract
Three-legged bosonic/fermionic magnetic ladder, reproducing the main features of magnetic lattice systems, is an ideal model to study the edge-bulk coupling and chiral edge dynamics, which ...are a hallmark of quantum Hall physics. Here, the ground state transition, localization, and chiral edge (bulk) states of an interacting three-legged bosonic magnetic ladder are studied analytically and numerically. When the system is in a quasi-steady state, using variational analysis, the threshold for the transition from zero momentum state to plane wave state is obtained. The energy spectrum, the ground state diagram, the chiral current of the system are presented, and the chiral current reversal at the state transition point is observed. Furthermore, the localization and its stability in the system are discussed, and rich localized phenomena (diffusion, breather, soliton, and self-trapping) are predicted. Stable soliton/breather prefers to form an edge state, while the self-trapping is favorite to form a bulk state, i.e. localized edge and bulk states are obtained. Particularly, for the unstable soliton in the ground state or metastable state, different kinds of chiral edge/bulk state and edge-bulk coupling are observed. The stability of the localized states, the edge-bulk coupling characteristics, and the chirality of the system depend on the energy band structure of the system. Additionally, a controllable transition between localized edge state and bulk state is realized by quenching the soliton state. We proposed a theoretical evidence to design and manipulate edge-bulk coupling and different kinds of localized/chiral edge (bulk) states in three-legged bosonic magnetic ladder.
Abstract
The interacting Bose–Hubbard flux ladder provides an ideal model to probe novel quantum phenomena of many-body systems. Here, we report on the first direct observation of dynamical quantum ...phase transition (DQPT) in interacting Bose–Hubbard flux ladder induced by defect perturbation, which provides a new scheme for experimental design and manipulation of the DQPT in ultracold atomic system. Under the mean-field approximation, DQPT is identified by resolving the order parameter and the temporal evolution of patterns of atomic density distributions and local current configurations of the system. The threshold for occurrence of DQPT is obtained analytical and the physical mechanism of DQPT is revealed explicitly. Periodic appearance and annihilation of dynamical vortex and the manifestation of symmetry restoration after perturbation from broken-symmetry phase are observed. A thorough connection among the order parameter dynamics, the underlying ground state phase transition and nonequilibrium dynamics is established in real time and real space for the first time. Interestingly, by quenching the defect, the underlying ground state phases are captured, which provides a feasible dynamical measurement scheme for the observation of the underlying ground state phase which is challenging to reach experimentally.
Based on particle-in-cell simulation and theoretical analysis, we demonstrate the possibility of the realization of the electric quadrupole radiation (EQR) and the quasi dipole radiation (QDR) modes ...at the THz band from the electrostatic oscillation of the electrons driven by the two-color lasers inside the plasma. Interestingly, an implantation of the external magnetic field will induce the flexible conversion between the EQR mode and the QDR mode. The emission angle, radiation frequency, and radiation field strength of the two radiation modes can be highly modulated by adjusting the intensity of the magnetic field, the frequency of the laser pulses, and the density of the plasma. This provides a new and practical way toward the generation and conversion of the multiple radiation modes, greatly extending the potential for optical manipulation in magnetized plasma.
ABSTRACT
The key enzymes involved in the flavonoid biosynthesis pathway have been extensively studied in seed plants, but relatively less in ferns. In this study, two 4‐Coumarate: coenzyme A ligases ...(Sc4CL1 and Sc4CL2) and one novel chalcone synthase (ScCHS1) were functionally characterized by mining the Stenoloma chusanum transcriptome database. Recombinant Sc4CLs were able to esterify various hydroxycinnamic acids to corresponding acyl‐coenzyme A (CoA). ScCHS1 could catalyze p‐coumaroyl‐CoA, cinnamoyl‐CoA, caffeoyl‐CoA, and feruloyl‐CoA to form naringenin, pinocembrin, eriodictyol, and homoeriodictyol, respectively. Moreover, enzymatic kinetics studies revealed that the optimal substrates of ScCHS1 were feruloyl‐CoA and caffeoyl‐CoA, rather than p‐coumaroyl‐CoA, which was substantially different from the common CHSs. Crystallographic and site‐directed mutagenesis experiments indicated that the amino acid residues, Leu87, Leu97, Met165, and Ile200, located in the substrate‐binding pocket near the B‐ring of products, could exert a significant impact on the unique catalytic activity of ScCHS1. Furthermore, overexpression of ScCHS1 in tt4 mutants could partially rescue the mutant phenotypes. Finally, ScCHS1 and Sc4CL1 were used to synthesize flavanones and flavones with multi‐substituted hydroxyl and methoxyl B‐ring in Escherichia coli, which can effectively eliminate the need for the cytochrome P450 hydroxylation/O‐methyltransferase from simple phenylpropanoid acids. In summary, the identification of these important Stenoloma enzymes provides a springboard for the future production of various flavonoids in E. coli.
Functional and structural characterization of a novel chalcone synthase from the fern Stenoloma chusanum, ScCHS1, revealed its promiscuous activity on various hydroxycinnamic acids. ScCHS1 was used to synthesize flavonoids with multi‐substituted hydroxyl and methoxyl B‐rings in E. coli.
Summary
Unlike bibenzyls derived from the vascular plants, lunularic acid (LA), a key precursor for macrocyclic bisbibenzyl synthesis in nonvascular liverworts, exhibits the absence of one hydroxy ...group within the A ring. It was hypothesized that both polyketide reductase (PKR) and stilbenecarboxylate synthase 1 (STCS1) were involved in the LA biosynthesis, but the underlined mechanisms have not been clarified.
This study used bioinformatics analysis with molecular, biochemical and physiological approaches to characterize STCS1s and PKRs involved in the biosynthesis of LA.
The results indicated that MpSTCS1s from Marchantia polymorpha catalyzed both C2→C7 aldol‐type and C6→C1 Claisen‐type cyclization using dihydro‐p‐coumaroyl‐coenzyme A (CoA) and malonyl‐CoA as substrates to yield a C6‐C2‐C6 skeleton of dihydro‐resveratrol following decarboxylation and the C6‐C3‐C6 type of phloretin in vitro. The protein–protein interaction of PKRs with STCS1 (PPI‐PS) was revealed and proved essential for LA accumulation when transiently co‐expressed in Nicotiana benthamiana. Moreover, replacement of the active domain of STCS1 with an 18‐amino‐acid fragment from the chalcone synthase led to the PPI‐PS greatly decreasing and diminishing the formation of LA. The replacement also increased the chalcone formation in STCS1s.
Our results highlight a previously unrecognized PPI in planta that is indispensable for the formation of LA.
See also the Commentary on this article by Davies & Andre, 237: 371–373.
The distribution of type I and II chalcone isomerases (CHIs) in plants is highly family specific. We have previously reported that ancient land plants, such as the liverworts and Selaginella ...moellendorffii, harbor type II CHIs. To better understand the function and evolution of CHI-fold proteins, transcriptomic data obtained from 52 pteridophyte species were subjected to sequence alignment and phylogenetic analysis. The residues determining type I/II CHI identity in the pteridophyte CHIs were identical to those of type I CHIs. The enzymatic characterization of a sample of 24 CHIs, representing all the key pteridophyte lineages, demonstrated that 19 of them were type I enzymes and that five exhibited some type II activity due to an amino acid mutation. Two pteridophyte chalcone synthases (CHSs) were also characterized, and a type IV CHI (CHIL) was demonstrated to interact physically with CHSs and CHI, and to increase CHS activity by decreasing derailment products, thus enhancing flavonoid production. These findings suggest that the emergence of type I CHIs may have coincided with the divergence of the pteridophytes. This study deepens our understanding of the molecular mechanism of CHIL as an enhancer in the flavonoid biosynthesis pathway.
Phytophthora genomes encode a myriad of Crinkler (CRN) effectors, some of which contain putative kinase domains. Little is known about the host targets of these kinase-domain-containing CRNs and ...their infection-promoting mechanisms. Here, we report the host target and functional mechanism of a conserved kinase CRN effector named CRN78 in a notorious oomycete pathogen, Phytophthora sojae. CRN78 promotes Phytophthora capsici infection in Nicotiana benthamiana and enhances P. sojae virulence on the host plant Glycine max by inhibiting plant H2O2 accumulation and immunity-related gene expression. Further investigation reveals that CRN78 interacts with PIP2-family aquaporin proteins including NbPIP2;2 from N. benthamiana and GmPIP2-13 from soybean on the plant plasma membrane, and membrane localization is necessary for virulence of CRN78. Next, CRN78 promotes phosphorylation of NbPIP2;2 or GmPIP2-13 using its kinase domain in vivo, leading to their subsequent protein degradation in a 26S-dependent pathway. Our data also demonstrates that NbPIP2;2 acts as a H2O2 transporter to positively regulate plant immunity and reactive oxygen species (ROS) accumulation. Phylogenetic analysis suggests that the phosphorylation sites of PIP2 proteins and the kinase domains of CRN78 homologs are highly conserved among higher plants and oomycete pathogens, respectively. Therefore, this study elucidates a conserved and novel pathway used by effector proteins to inhibit host cellular defenses by targeting and hijacking phosphorylation of plant aquaporin proteins.
The nonequilibrium quantum dynamics and nonlinear chiral Bloch oscillation in interacting flux ladder induced by arbitrarily distributed defects are studied analytically and numerically. Under a ...time-dependent two-mode approximation, the system with arbitrarily distributed defects can be deduced to the case with single defect and the dynamical behavior of the system can be predicted analytically. The nontrivial competition between the atomic interaction and defects causes the system to undergo a dynamical quantum phase transition (DQPT) which can be identified by the chiral Bloch oscillation induced by the defects. Importantly, the DQPT is not only related to the underlying ground state of the system but also to the properties of the defects. The DQPT can be well modulated by different types of defects. This work provides a feasible theoretical scheme for the experimental design and operation of DQPT by defect perturbations.
•The nonequilibrium dynamics and chiral Bloch oscillation in flux ladder induced by defects are studied.•Under a time-dependent two-mode approximation, the system can be mapped onto a single defect system.•DQPT can be identified by the chiral characteristics of the Bloch oscillation induced by defects.•The DQPT can be well modulated by different types of defects.•We propose an efficient way to manipulate the DQPT in controllable way by defect perturbations.
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