Plant Cells Research Articles

Photoactive hyperbranched poly(azo‐ester) urethanes as fluorescent staining agent for plant cells

Photoactive hyperbranched poly(azo‐ester) urethanes as fluorescent staining agent for plant cells

Mechanistic insights to Paenibacillus lentimorbus mediated biocontrol of Alternaria solani in Solanum lycopersicum L. through carbohydrate reallocation and sweet immunity suppression

Researchers envisaged that PGPR (plant growth promoting rhizobacteria) has vast possibilities as a bioinoculant that will lead to revolution. However, it's still very far from becoming commercially successful. Here, the information regarding the root colonization of PGPR in host plants and plant response towards PGPR is inadequate. It can provide valuable information for developing successful biofertilizers and biocontrol agents. PGPR (Paenibacillus lentimorbus NRRL B-30488 or CHM12) has been previously reported as a successful commercial biofertilizer and biocontrol agent. However, the exact mechanism of plant growth promotion and biocontrol is poorly studied. So, CHM12 was appraised for biotic stress amelioration of pathogen Alternaria solani in Tomato (Solanum lycopersicum L.) var. S-22 plants. PGPR CHM12 was assessed for various plant growth parameters such as proline, sugar content, etc. in pathogen A. solani (AS) challenged plants and compared with the CHM12 treated plants in a greenhouse study. Then, the metabolomics tool (GC-MS) was used to identify metabolites and their respective genes playing pivotal roles in colonization tactics availed by PGPR. Further, gene expression analysis was done to affirm the involvement of various genes related to metabolites providing biotic stress tolerance in Tomato plants. The current research discerned that PGPR CHM12 revealed significant differences in different plant growth parameters studied. There were 33 distinct metabolites identified, which stipulated the involvement of carbohydrate metabolism mainly in combating biotic stress in this study. Thus, our study reconfirmed very few reported previous results through gene expression analysis, suggesting the downregulation of carbohydrate metabolism genes in PGPR-treated plants. This downregulation of carbohydrate genes might be the critical factor for suppressing the plant's immune response to gaining entry inside the host plant. This also helps in retaining and reallocating carbohydrates in plant cells to reduce pathogen proliferation.

In Situ Enzymatic Polymerization of Ethylene Brassylate Mediated by Artificial Plant Cell Walls in Reactive Extrusion.

Herein, we describe a solvent-free bioinspired approach for the polymerization of ethylene brassylate. Artificial plant cell walls (APCWs) with an integrated enzyme were fabricated by self-assembly, using microcrystalline cellulose as the main structural component. The resulting APCW catalysts were tested in bulk reactions and reactive extrusion, leading to high monomer conversion and a molar mass of around 4 kDa. In addition, we discovered that APCW catalyzes the formation of large ethylene brassylate macrocycles. The enzymatic stability and efficiency of the APCW were investigated by recycling the catalyst both in bulk and reactive extrusion. The obtained poly(ethylene brassylate) was applied as a biobased and biodegradable hydrophobic paper coating.

Chitosan stimulates root hair callose deposition, endomembrane dynamics, and inhibits root hair growth.

Although angiosperm plants generally react to immunity elicitors like chitin or chitosan by the cell wall callose deposition, this response in particular cell types, especially upon chitosan treatment, is not fully understood. Here we show that the growing root hairs (RHs) of Arabidopsis can respond to a mild (0.001%) chitosan treatment by the callose deposition and by a deceleration of the RH growth. We demonstrate that the glucan synthase-like 5/PMR4 is vital for chitosan-induced callose deposition but not for RH growth inhibition. Upon the higher chitosan concentration (0.01%) treatment, RHs do not deposit callose, while growth inhibition is prominent. To understand the molecular and cellular mechanisms underpinning the responses to two chitosan treatments, we analysed early Ca2+ and defence-related signalling, gene expression, cell wall and RH cellular endomembrane modifications. Chitosan-induced callose deposition is also present in the several other plant species, including functionally analogous and evolutionarily only distantly related RH-like structures such as rhizoids of bryophytes. Our results point to the RH callose deposition as a conserved strategy of soil-anchoring plant cells to cope with mild biotic stress. However, high chitosan concentration prominently disturbs RH intracellular dynamics, tip-localised endomembrane compartments, growth and viability, precluding callose deposition.

Gene isolation and enzymatic characterization of UDP-glycosyltransferases of terpene glucoside biosynthesis involved in linalyl-glycoside accumulation in Coffea arabica

Terpenes, one of the secondary metabolites produced by plants, have diverse physiological functions. They are volatile compounds with physiological bioactivities (e.g., insect repellent, attracting enemies, and interacting with other plants). Terpenoids are also essential for flavor and aroma in plant-derived foods. In coffee, its aroma decides the value of coffee beans. Linalool, one of the volatile terpene compounds, is dominant in the coffee aroma. Coffee, with its good flavor and aroma, has high demand worldwide. Because terpenoids generally accumulate as glycosides in plant cells, glycosylation is catalyzed by UDP-glycosyltransferases (UGTs). Two linalyl-diglycosides have been identified: terpenoids reflected as necessary for coffee flavor. However, these UGTs and their action mechanisms are unknown in the Coffea genus. To obtain knowledge of terpene UGTs and elucidate the mechanism of terpene glycosylation in coffee, this study isolated terpene UGT genes and analyzed their functions. In silico screening based on the sequence of UGT85K11, which catalyzes terpene glycosylation from Camellia sinensis, was performed to obtain sequence information on five candidate UGT genes (CaUGT4, CaUGT5, CaUGT10, CaUGT15, and CaUGT20). These genes were isolated by reverse transcription-polymerase chain reaction, and the recombinant enzymes were produced with the Escherichia coli expression system. In functional analysis using radioisotopes, CaUGT4 showed critical activity against linalool, which had a higher affinity for its substrate than that of UGT85A84 from Osmanthus fragrans. Liquid chromatography-tandem mass spectrometry also revealed that CaUGT4 mainly produces linalyl glucoside. In this study, the first linalyl UGT was isolated from coffee. These findings can be used to elucidate the fundamental mechanism of the chemical defense in plants and apply aroma precursors for the plant-derived food industry in the future.

The Epsin-like clathrin adaptor protein 4 SlECA4 improves tomato heat tolerance via clathrin-mediated endocytosis.

Clathrin-mediated endocytosis (CME) is one of the main pathways for plant cells to internalize the membrane proteins in response to changing environmental conditions. The Epsin-like Clathrin adaptor proteins (ECAs) play important roles in the assembly of clathrin coat; however, their involvement in plant response to heat stress remains unclear. Here we report that SlECA4 responded to heat stress, and the silencing and knockout of SlECA4 increased tomato sensitivity to heat stress, while the overexpression of SlECA4 enhanced tomato tolerance to heat stress. Meanwhile, the treatment with a CME inhibitor, ES9-17, reduced tomato heat tolerance. SlECA4 localized to the plasma membrane (PM), the trans-Golgi network/early endosomes (TGN/EE), and the prevacuolar compartment (PVC)/late endosomes. In SlECA4-KO line, both CME and recycling from the TGN/EE to the PM were inhibited. These data suggest that SlECA4 involved in CME. After heat treatment, more punctate structures of SlECA4:GFP accumualted in tobacco leaf epidermal cells by transient expression. Furthermore, compared to WT, the rate of CME was inhibited under heat stress in SlECA4-KO line. Taken together, the Epsin-like Clathrin adaptor protein SlECA4 plays a positive role in tomato tolerance to heat stress via the CME pathway.

Resolving the metabolism of monolignols and other lignin-related aromatic compounds in Xanthomonas citri

Lignin, a major plant cell wall component, has an important role in plant-defense mechanisms against pathogens and is a promising renewable carbon source to produce bio-based chemicals. However, our understanding of microbial metabolism is incomplete regarding certain lignin-related compounds like p-coumaryl and sinapyl alcohols. Here, we reveal peripheral pathways for the catabolism of the three main lignin precursors (p-coumaryl, coniferyl, and sinapyl alcohols) in the plant pathogen Xanthomonas citri. Our study demonstrates all the necessary enzymatic steps for funneling these monolignols into the tricarboxylic acid cycle, concurrently uncovering aryl aldehyde reductases that likely protect the pathogen from aldehydes toxicity. It also shows that lignin-related aromatic compounds activate transcriptional responses related to chemotaxis and flagellar-dependent motility, which might play an important role during plant infection. Together our findings provide foundational knowledge to support biotechnological advances for both plant diseases treatments and conversion of lignin-derived compounds into bio-based chemicals.

Leaf-like MSX/TiN heterojunction photocathodes mimicking plant cell – An effective strategy to enhance photoelectrocatalytic carbon dioxide reduction and systematic mechanism investigation

Semiconductors, such as metal oxides and metal sulfides (MSX), are widely investigated as effectively catalytic materials to convert carbon dioxide (CO2) and water into chemicals under simulated solar light. These valuable investigations might address both the energy crisis and climate change in our modern society. Herein, a novel strategy to construct leaf-like heterojunctions of VS-ZnIn2S4/TiN-x is reported. The new semiconductor heterojunctions were then applied to photoelectrocatalytic CO2 reduction, achieving excellent performance (formate formation rate of 1173.2 μM h−1 cm−2) attributed to the plant cell-like morphology and enhanced electron mobility from the heterojunction interfaces to the active sites on the surface. Our findings suggest that titanium nitride (TiN) with good conductivity can improve the photoelectrocatalytic ability of MSX through heterojunction construction. The photocathode VS-ZnIn2S4/TiN-3 exhibits 81.0 % selectivity toward C2 products by optimizing the material structure and reaction conditions. According to the systematic investigation of operando Fourier transform infrared (FTIR) spectra, common intermediates such as *COO−, *COOH, *CO, *CHO, *COCHO, and *COCH3 reported in the literature were carefully verified. Among these, the carbene specie serve as the key intermediate responsible for generating other intermediates and resulting in all products.

How coat proteins shape autophagy in plant cells.

Autophagy is a membrane trafficking pathway through which eukaryotic cells target their own cytoplasmic constituents for degradation in the lytic compartment. Proper biogenesis of autophagic organelles requires a conserved set of autophagy-related (ATG) proteins and their interacting factors, such as signalling phospholipid phosphatidylinositol 3-phosphate (PI3P) and coat complex II (COPII). The COPII machinery, which was originally identified as a membrane coat involved in the formation of vesicles budding from the endoplasmic reticulum, contributes to the initiation of autophagic membrane formation in yeast, metazoan, and plant cells; however, the exact mechanisms remain elusive. Recent studies using the plant model species Arabidopsis thaliana have revealed that plant-specific PI3P effectors are involved in autophagy. The PI3P effector FYVE2 interacts with the conserved PI3P effector ATG18 and with COPII components, indicating an additional role for the COPII machinery in the later stages of autophagosome biogenesis. In this Update, we examined recent research on plant autophagosome biogenesis and proposed working models on the functions of the COPII machinery in autophagy, including its potential roles in stabilizing membrane curvature and sealing the phagophore.

Lead phosphate prepared from spent lead compounds as a negative additive for lead-acid batteries

Lead phosphate prepared from spent lead compounds as a negative additive for lead-acid batteries

Performance enhancement of lead‑carbon batteries by bi-based metal-organic framework-derived carbon materials

Lead‑carbon batteries (LCBs) cannot replace lead-acid batteries for large-scale applications in daily life due to the acceleration of hydrogen evolution reaction by carbon materials during the cycling process. In this study, we selected a Bi-based metal-organic framework as a carbon precursor, and prepared carbon composites containing Bi and its oxides (Bi@C) via a simple calcination method. The composites were characterized and tested for battery performance. The results show that the inherent rod-like structure of Bi@C material still exists at 600 °C and it effectively improves the conductivity of the negative active material (NAM). Under HRPSoC conditions, the battery with 2 % Bi@C reaches a cycle life of 7331 cycles, 3.9 times that of a blank battery. The improved performance of LCBs is attributed to the high conductivity, hydrogen evolution suppression ability and uniqe rod-like structure of Bi@C material, which effectively increase the conversion rate of active materials, thus extending the battery lifespan. This research provides a more economical and simpler approach for optimizing the combination of carbon with other metal elements to address the problem of hydrogen evolution in lead‑carbon batteries.

T6SS in plant pathogens: unique mechanisms in complex hosts.

Type VI secretion systems (T6SSs) are complex molecular machines that allow bacteria to deliver toxic effector proteins to neighboring bacterial and eukaryotic cells. Although initial work focused on the T6SS as a virulence mechanism of human pathogens, the field shifted to examine the use of T6SSs for interbacterial competition in various environments, including in the plant rhizosphere. Genes encoding the T6SS are estimated to be found in a quarter of all Gram-negative bacteria and are especially highly represented in Proteobacteria, a group which includes the most important bacterial phytopathogens. Many of these pathogens encode multiple distinct T6SS gene clusters which can include the core components of the apparatus as well as effector proteins. The T6SS is deployed by pathogens at multiple points as they colonize their hosts and establish an infection. In this review, we describe what is known about the use of T6SS by phytopathogens against plant hosts and non-plant organisms, keeping in mind that the structure of plants requires unique mechanisms of attack that are distinct from the mechanisms used for interbacterial interactions and against animal hosts. While the interactions of specific effectors (such as phospholipases, endonucleases, peptidases, and amidases) with targets have been well described in the context of interbacterial competition and in some eukaryotic interactions, this review highlights the need for future studies to assess the activity of phytobacterial T6SS effectors against plant cells.

Systemic delivery of engineered compact AsCas12f by a positive-strand RNA virus vector enables highly efficient targeted mutagenesis in plants.

Because virus vectors can spread systemically autonomously, they are powerful vehicles with which to deliver genome-editing tools into plant cells. Indeed, a vector based on a positive-strand RNA virus, potato virus X (PVX), harboring SpCas9 and its single guide RNA (sgRNA), achieved targeted mutagenesis in inoculated leaves of Nicotiana benthamiana. However, the large size of the SpCas9 gene makes it unstable in the PVX vector, hampering the introduction of mutations in systemic leaves. Smaller Cas variants are promising tools for virus vector-mediated genome editing; however, they exhibit far lower nuclease activity than SpCas9. Recently, AsCas12f, one of the smallest known Cas proteins so far (one-third the size of SpCas9), was engineered to improve genome-editing activity dramatically. Here, we first confirmed that engineered AsCas12f variants including I123Y/D195K/D208R/V232A exhibited enhanced genome-editing frequencies in rice. Then, a PVX vector harboring this AsCas12f variant was inoculated into N. benthamiana leaves by agroinfiltration. Remarkably, and unlike with PVX-SpCas9, highly efficient genome editing was achieved, not only in PVX-AsCas12f-inoculated leaves but also in leaves above the inoculated leaf (fourth to sixth upper leaves). Moreover, genome-edited shoots regenerated from systemic leaves were obtained at a rate of >60%, enabling foreign DNA-free genome editing. Taken together, our results demonstrate that AsCas12f is small enough to be maintained in the PVX vector during systemic infection in N. benthamiana and that engineered AsCas12f offers advantages over SpCas9 for plant genome editing using virus vectors.

Modern Technologies Provide New Opportunities for Somatic Hybridization in the Breeding of Woody Plants.

Advances in cell fusion technology have propelled breeding into the realm of somatic hybridization, enabling the transfer of genetic material independent of sexual reproduction. This has facilitated genome recombination both within and between species. Despite its use in plant breeding for over fifty years, somatic hybridization has been limited by cumbersome procedures, such as protoplast isolation, hybridized-cell selection and cultivation, and regeneration, particularly in woody perennial species that are difficult to regenerate. This review summarizes the development of somatic hybridization, explores the challenges and solutions associated with cell fusion technology in woody perennials, and outlines the process of protoplast regeneration. Recent advancements in genome editing and plant cell regeneration present new opportunities for applying somatic hybridization in breeding. We offer a perspective on integrating these emerging technologies to enhance somatic hybridization in woody perennial plants.

Arabidopsis hydathodes are sites of auxin accumulation and nutrient scavenging.

Hydathodes are small organs found on the leaf margins of vascular plants which release excess xylem sap through a process called guttation. While previous studies have hinted at additional functions of hydathode in metabolite transport or auxin metabolism, experimental support is limited. We conducted comprehensive transcriptomic, metabolomic and physiological analyses of mature Arabidopsis hydathodes. This study identified 1460 genes differentially expressed in hydathodes compared to leaf blades, indicating higher expression of most genes associated with auxin metabolism, metabolite transport, stress response, DNA, RNA or microRNA processes, plant cell wall dynamics and wax metabolism. Notably, we observed differential expression of genes encoding auxin-related transcriptional regulators, biosynthetic processes, transport and vacuolar storage supported by the measured accumulation of free and conjugated auxin in hydathodes. We also showed that 78% of the total content of 52 xylem metabolites was removed from guttation fluid at hydathodes. We demonstrate that NRT2.1 and PHT1;4 transporters capture nitrate and inorganic phosphate in guttation fluid, respectively, thus limiting the loss of nutrients during this process. Our transcriptomic and metabolomic analyses unveil an organ with its specific physiological and biological identity.

Biomimetic structure-driven high strength and toughness in continuous SiC skeleton-reinforced graphite composites

Graphite-matrix structural composites with excellent mechanical properties and long-term reliability are ungently required in aerospace and nuclear industries. However, the enhancement of graphite-matrix composites by mainstream surface coating techniques or second-phase particle reinforcement is rather limited. Inspired by the structural-functional feature of plant cells, silicon carbide (SiC, cytoderm) coated mesocarbon microbeads (MCMB, cytoplasm) powders were prepared by combustion synthesis (CS), which were then densified via spark plasma sintering (SPS) to obtain the biomimetic cellular-structured SiC-reinforced MCMB (M@SiC) composites. The in-situ formed SiC ‘cytoderm’ ensures good interfacial bonding and contributed to the densification of the composites. Additionally, the continuous SiC skeleton and cellular-structured configuration improved the mechanical properties of M@SiC composites. Owing to the complex crack deflection, branching and bridging effects at the MCMB/SiC interfaces and graphite nanoflakes inside MCMB, the biomimetic M@SiC composite with SiC content of 47 vol% exhibited strengthening and toughening, with flexural strength and fracture toughness of 245 MPa and 3.82 MPa m1/2, respectively. The developed biomimetic graphite-matrix composites with excellent mechanical properties are expected to be applied in reusable spacecrafts and high-temperature gas-cooled reactors.

Varying Tolerance to Diesel Toxicity Revealed by Growth Response Evaluation of Petunia grandiflora Shoot Lines Regenerated after Diesel Fuel Treatment

Continuous efforts are required to find ways to protect crop production against the toxicity of petroleum hydrocarbons, such as diesel, and contamination of soils. There is a need for identification of candidate plants that are tolerant to diesel toxicity that might also have the potential for remediation of diesel-contaminated soils. In this study, petunia, a popular ornamental plant and a model experimental plant in research on phytoremediation of environmental pollutants, was used to evaluate a novel method for rapidly assessing diesel toxicity based on the tolerance of shoots generated through in vitro plant cell culture selection. Petunia shoot lines (L1 to L4) regenerated from diesel-treated callus were compared with those from non-diesel-treated callus (control). Significant morphological differences were observed among the tested lines and control, notably with L1 and L4 showing superior growth. In particular, L4 exhibited remarkable adaptability, with increased root development and microbial counts in a diesel-contaminated potting mix, suggesting that the shoots exhibited enhanced tolerance to diesel exposure. Here, this rapid bioassay has been shown to effectively identify plants with varying levels of tolerance to diesel toxicity and could therefore assist accelerated selection of superior plants for phytoremediation. Further research is needed to understand the genetic and physiological mechanisms underlying tolerance traits, with potential applications beyond petunias to other environmentally significant plants.

First draft genome sequence of a Pectobacterium polaris strain isolated in South Africa from potato tuber affected by soft rot.

A phytopathogenic strain of Pectobacterium polaris (designated SRB2) was isolated for the first time in South Africa from a potato tuber affected by soft rot. The draft genome of strain SRB2 encodes various plant cell wall-degrading enzymes and genes associated with biofilm formation and virulence. Antibiotic resistance genes were not detected.

Advances in Plant Auxin Biology: Synthesis, Metabolism, Signaling, Interaction with Other Hormones, and Roles under Abiotic Stress.

Auxin is a key hormone that regulates plant growth and development, including plant shape and sensitivity to environmental changes. Auxin is biosynthesized and metabolized via many parallel pathways, and it is sensed and transduced by both normal and atypical pathways. The production, catabolism, and signal transduction pathways of auxin primarily govern its role in plant growth and development, and in the response to stress. Recent research has discovered that auxin not only responds to intrinsic developmental signals, but also mediates various environmental signals (e.g., drought, heavy metals, and temperature stresses) and interacts with hormones such as cytokinin, abscisic acid, gibberellin, and ethylene, all of which are involved in the regulation of plant growth and development, as well as the maintenance of homeostatic equilibrium in plant cells. In this review, we discuss the latest research on auxin types, biosynthesis and metabolism, polar transport, signaling pathways, and interactions with other hormones. We also summarize the important role of auxin in plants under abiotic stresses. These discussions provide new perspectives to understand the molecular mechanisms of auxin's functions in plant development.

Complete genome sequence analysis of Pestalotiopsis microspora, a fungal pathogen causing kiwifruit postharvest rots

BackgroundThe postharvest rot of kiwifruit is one of the most devastating diseases affecting kiwifruit quality worldwide. However, the genomic basis and pathogenicity mechanisms of kiwifruit rot pathogens are lacking. Here we report the first whole genome sequence of Pestalotiopsis microspora, one of the main pathogens causing postharvest kiwifruit rot in China. The genome of strain KFRD-2 was sequenced, de novo assembled, and analyzed.ResultsThe genome of KFRD-2 was estimated to be approximately 50.31 Mb in size, with an overall GC content of 50.25%. Among 14,711 predicted genes, 14,423 (98.04%) exhibited significant matches to genes in the NCBI nr database. A phylogenetic analysis of 26 known pathogenic fungi, including P. microspora KFRD-2, based on conserved orthologous genes, revealed that KFRD-2’s closest evolutionary relationships were to Neopestalotiopsis spp. Among KFRD-2’s coding genes, 870 putative CAZy genes spanned six classes of CAZys, which play roles in degrading plant cell walls. Out of the 25 other plant pathogenic fungi, P. microspora possessed a greater number of CAZy genes than 22 and was especially enriched in GH and AA genes. A total of 845 transcription factors and 86 secondary metabolism gene clusters were predicted, representing various types. Furthermore, 28 effectors and 109 virulence-enhanced factors were identified using the PHI (pathogen host-interacting) database.ConclusionThis complete genome sequence analysis of the kiwifruit postharvest rot pathogen P. microspora enriches our understanding its disease pathogenesis and virulence. This study establishes a theoretical foundation for future investigations into the pathogenic mechanisms of P. microspora and the development of enhanced strategies for the efficient management of kiwifruit postharvest rots.