Silencing of the T-type voltage-gated calcium channel α1 subunit by fungus-mediated RNAi altered the structure of F-actin and caused defective behaviors in Ditylenchus destructor.

BACKGROUND: T-type calcium channels, characterized as low-voltage activated (LVA) calcium channels, play crucial physiological roles across a wide range of tissues, including both the neuronal and nonneuronal systems. Using in situ hybridization and RNA interference (RNAi) techniques in vitro, we previously identified the tissue distribution and physiological function of the T-type calcium channel α1 subunit (DdCα1G) in the plant-parasitic nematode Ditylenchus destructor. METHODS AND RESULTS: To further characterize the functional role of DdCα1G, we employed a combination of immunohistochemistry and fungus-mediated RNAi and found that DdCα1G was clearly distributed in stylet-related tissue, oesophageal gland-related tissue, secretory-excretory duct-related tissue and male spicule-related tissue. Silencing DdCα1G led to impairments in the locomotion, feeding, reproductive ability and protein secretion of nematodes. To confirm the defects in behavior, we used phalloidin staining to examine muscle changes in DdCα1G-RNAi nematodes. Our observations demonstrated that defective behaviors are associated with related muscular atrophy. CONCLUSION: Our findings provide a deeper understanding of the physiological functions of T-type calcium channels in plant-parasitic nematodes. The T-type calcium channel can be considered a promising target for sustainable nematode management practices.

Clarifying the Functional Role of Serotonin in Meloidogyne graminicola Host Plant Parasitism by Immunolocalization and RNA Interference.

Serotonin (5-hydroxytryptamine) is an essential neurotransmitter involved in regulating various behaviors in plant-parasitic nematodes, including locomotion, egg laying, feeding, and mating. However, the functional role of serotonin in root-knot nematode invasion of host plants and the molecular mechanisms underlying feeding behavior remain poorly understood. In this study, we tested the effects of exogenous serotonin and the pharmacological compounds fluoxetine and methiothepin on the feeding behaviors of Meloidogyne graminicola. Our results suggested that M. graminicola possesses an endogenous serotonin signaling pathway and that serotonin plays a crucial role in modulating feeding behaviors in M. graminicola second-stage juveniles. We also identified and cloned the serotonin synthesis enzyme tryptophan hydroxylase (Mg-tph-1) in M. graminicola and investigated the role of endogenous serotonin by generating RNA interference nematodes in Mg-tph-1. Silencing Mg-tph-1 substantially reduced nematode invasion, development, and reproduction. According to the immunostaining results, we speculated that these serotonin immunoreactive cells near the nerve ring in M. graminicola are likely homologous to Caenorhabditis elegans ADFs, NSMs, and RIH serotonergic neurons. Furthermore, we investigated the impact of phytoserotonin on nematode invasion and development in rice by overexpressing OsTDC-3 or supplementing rice plants with tryptamine and found that an increase in phytoserotonin increases nematode pathogenicity. Overall, our study provides insights into the essential role of serotonin in M. graminicola host plant parasitism and proposes that the serotonergic signaling pathway could be a potential target for controlling plant-parasitic nematodes.

Population dynamics of Meloidogyne graminicola in soil in different types of direct-seeded rice agroecosystems in Hunan Province, China.

The rice root-knot nematode Meloidogyne graminicola is increasingly widely distributed in China and has had a severe incidence in Hunan Province. It is thus necessary to investigate its population dynamics in paddy fields. This study was conducted to ascertain the effect of direct-seeded rice agroecosystems on the population dynamics of M. graminicola and root gall development in rice. The results indicated that the population density of M. graminicola in soil was markedly influenced by the agroecosystem, rainfall and temperature. The population density of M. graminicola J2, and eggs in the soil and root galls, were significantly larger in the dry aerobic rice agroecosystem and in the rain-fed upland agroecosystem than in the lowland double-rice cropping sequence agroecosystem. As it can affect soil moisture rainfall was the key factor affecting the density of nematodes in both the rain-fed upland agroecosystem and the dry aerobic rice agroecosystem. Field flooding was still an effective way to reduce the population density of M. graminicola. In addition, we observed that M. graminicola can lay eggs outside rice roots under laboratory conditions. Therefore, we propose a hypothesis that M. graminicola lays egg masses within roots when the soil moisture is high, but lays eggs outside when the soil moisture is suitable. By clarifying the population dynamics of M. graminicola in different types of direct-seeded rice agroecosystems, this study is conducive to controlling rice root-knot nematodes.

The α2δ Calcium Channel Subunit Accessorily and Independently Affects the Biological Function of Ditylenchus destructor.

The α2δ subunit is a high-voltage activated (HVA) calcium channel (Cav1 and Cav2) auxiliary subunit that increases the density and function of HVA calcium channels in the plasma membrane of mammals. However, its function in plant parasitic nematodes remains unknown. In this study, we cloned the full-length cDNA sequence of the voltage-gated calcium channel (VGCC) α2δ subunit (named DdCavα2δ) in Ditylenchus destructor. We found that DdCavα2δ tends to be expressed in the egg stage, followed by the J3 stage. RNA-DIG in situ hybridization experiments showed that the DdCavα2δ subunit was expressed in the body wall, esophageal gland, uterus, post uterine, and spicules of D. destructor. The in vitro application of RNA interference (RNAi) affected the motility, reproduction, chemotaxis, stylet thrusting, and protein secretion of D. destructor to different degrees by targeting DdCα1D, DdCα1A, and DdCavα2δ in J3 stages, respectively. Based on the results of RNAi experiments, it was hypothesized that L-type VGCC may affect the motility, chemotaxis, and stylet thrusting of D. destructor. Non-L-type VGCC may affect the protein secretion and reproduction of D. destructor. The DdCavα2δ subunit gene also affected the motility, chemotaxis, and reproduction of D. destructor. These findings reveal the independent function of the VGCC α2δ subunit in D. destructor as well as give a theoretical foundation for future research on plant parasitic nematode VGCC.

Biocontrol potential of Pseudomonas rhodesiae GC-7 against the root-knot nematode Meloidogyne graminicola through both antagonistic effects and induced plant resistance.

Plant-parasitic nematodes (PPNs) cause serious damage to agricultural production worldwide. Currently, because of a lack of effective and environmental-friendly chemical nematicides, the use of microbial nematicides has been proposed as an eco-friendly management strategy to control PPNs. A nematicidal bacterium GC-7 was originally isolated from the rice rhizosphere, and was identified as Pseudomonas rhodesiae. Treatment with the fermentation supernatant of GC-7 in vitro showed a highly lethal effect on second-stage juveniles of Meloidogyne graminicola, with the mortality rate increasing to 95.82% at 24 h and egg hatching significantly inhibited, with a hatch inhibition rate of 60.65% at 96 h. The bacterium significantly reduced the level of damage caused by M. graminicola infestations to rice (Oryza sativa) in greenhouse and field experiments. Under greenhouse conditions, the GC-7 culture efficiently reduced the gall index and nematode population in rice roots and soils, as well as inhibited nematode development compared to the control. Under field conditions, application of the GC-7 consistently showed a high biocontrol efficacy against M. graminicola (with a control efficiency of 58.85%) and promoted plant growth. In addition, the inoculation of GC-7 in M. graminicola-infested rice plant fields significantly suppressed final nematode populations in soil under natural conditions. Furthermore, activities of plant defense-related enzymes, peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase were remarkably increased in plant roots treated with GC-7 compared with roots that were challenge to M. graminicola. Moreover, quantitative real-time PCR analysis showed that GC-7 significantly enhanced the expression of defense genes (PR1a, WRKY45, JaMYB, AOS2, ERF1, and ACS1) related to salicylic acid, jasmonic acid, and ethylene signaling pathways in rice roots after inoculation with GC-7 at different levels. The results indicated that GC-7 could be an effective biological component in the integrated management of M. graminicola infecting rice.

[Comprehensive evaluation of salt-alkali tolerance of rice germplasms at germination and seedling stages and analysis of salt-tolerant genes].

Cultivating salt-alkali tolerant rice varieties is one of the important ways to meet the increasing food demand of growing global population. In this study, twenty-one rice germplasms with different salt-alkali tolerance were treated with six salt-alkali concentrations at germination and seedling stages. The germination potential, germination rate, shoot length, root length, root number, fresh weight of shoot and seedlings were measured. The average value of salt damage rate was used to evaluate the salt-alkali tolerance. As the salt-alkali concentration increases, the inhibition on seed germination and growth became more obvious. Upon treatment with 1% NaCl plus 0.25% NaHCO3, the salt damage rate of germination rate has the largest variation, ranging from 0% to 89.80%. The salt damage rate of each trait shows a similar trend at all concentrations. Four germplasm resources with strong salt-alkali tolerance (Dajiugu, Nippobare, Mowanggu and 02428) and 7 sensitive germplasms were screened. The salt-tolerant gene sequence of 4 salt-alkali tolerant varieties and 3 sensitive germplasms were analyzed. OSHAL3 and OsRR22 were identical among the 7 germplasms, but SKC1 and DST showed clear variations between the salt-alkali tolerant and sensitive germplasms. Besides the salt-alkali tolerant germplasm resources, this study can also serve as a reference for mining of genes involved in salt-alkali tolerance and breeding of salt-alkali tolerant rice varieties.

Co-Silencing of the Voltage-Gated Calcium Channel ß Subunit and High-Voltage Activated α1 Subunit by dsRNA Soaking Resulted in Enhanced Defects in Locomotion, Stylet Thrusting, Chemotaxis, Protein Secretion, and Reproduction in Ditylenchus destructor.

The voltage-gated calcium channel (VGCC) ß subunit (Cavß) protein is a kind of cytosolic auxiliary subunit that plays an important role in regulating the surface expression and gating characteristics of high-voltage-activated (HVA) calcium channels. Ditylenchus destructor is an important plant-parasitic nematode. In the present study, the putative Cavß subunit gene of D. destructor, namely, DdCavß, was subjected to molecular characterization. In situ hybridization assays showed that DdCavß was expressed in all nematode tissues. Transcriptional analyses showed that DdCavß was expressed during each developmental stage of D. destructor, and the highest expression level was recorded in the third-stage juveniles. The crucial role of DdCavß was verified by dsRNA soaking-mediated RNA interference (RNAi). Silencing of DdCavß or HVA Cavα1 alone and co-silencing of the DdCavß and HVA Cavα1 genes resulted in defective locomotion, stylet thrusting, chemotaxis, protein secretion and reproduction in D. destructor. Co-silencing of the HVA Cavα1 and Cavß subunits showed stronger interference effects than single-gene silencing. This study provides insights for further study of VGCCs in plant-parasitic nematodes.

Effects of vacuum ultrasonic treatment on the texture of vegetarian meatloaves made from textured wheat protein.

To improve the quality of vegetarian meatloaves (VMs) made from textured wheat protein, the effects of different treatments (Vacuum, ultrasound and vacuum ultrasound) were compared in terms of texture, moisture distribution, microstructure and chemical bonding interactions. After vacuum, ultrasonic, and vacuum ultrasonic treatments, the hardness of VMs increased by 78%, 66%, 176% respectively. Scanning electron microscopy (SEM) showed that surface of VMs was smoother and the structure was tighter after vacuum ultrasonic treatment. In addition, magnetic resonance imaging (MRI) analysis showed that the moisture in VMs was evenly distributed after vacuum ultrasonic treatment. According to the optical maps observed by spectrofluorimetry and Fourier transform infrared spectroscopy (FT-IR), the fluorescence value and relative content of ß-sheet increased after vacuum ultrasonic treatment. Furthermore, the protein was cross-linked and hydrophobic interactions increased after vacuum ultrasonic treatment. Results showed that texture of VMs after vacuum ultrasonic treatment was closer to that of beef patties.

Roles of FERONIA-like receptor genes in regulating grain size and quality in rice.

Grain yield and quality are critical factors that determine the value of grain crops. In this study, we analyzed the functions of 12 FERONIA-like receptor (FLR) family members in rice and investigated their effects on grain size and quality. We found that FLR1, FLR2 and FLR8 negatively regulated grain size, and FLR15 positively regulated grain size. flr1 mutants had a higher cell number and an accelerated rate of grain filling compared to wild-type plants, which led to grains with greater widths. A mechanism underlying the regulation of grain size by FLR1 is that FLR1 is associated with OsRac1 Rho-like GTPase, a positive regulator of grain size. Regarding grain quality, the flr1 mutant had a higher percentage of chalkiness compared with wild-type plants, and seeds carrying mutations in flr3 and flr14 had endosperms with white floury cores. To elucidate the possible mechanism underlying this phenomenon, we found that FLR1 was constitutively expressed during endosperm development. RNA-seq analysis identified 2,367 genes that were differentially expressed in the flr1 mutant, including genes involved in starch and sucrose metabolism and carbon fixation. In this study, we identified the roles played by several FLR genes in regulating grain size and quality in rice and provided insights into the molecular mechanism governing the FLR1-mediated regulation of grain size.

RALF-FERONIA Signaling: Linking Plant Immune Response with Cell Growth.

Plants perceive various external and internal signals to self-modulate biological processes through members of the receptor-like kinase (RLK) family, among which Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) proteins with their ligands, rapid alkalinization factor (RALF) peptides, have attracted considerable interest. FERONIA (FER), a CrRLK1L member, was initially reported to act as a major plant cell growth modulator in distinct tissues. Subsequently, the RALF-FER pathway was confirmed to function as an essential regulator of plant stress responses, including but not limited to immune responses. Furthermore, the RALF-FER pathway modulates immune responses and cell growth in a context-specific manner, and the vital roles of this pathway are beginning to be appreciated in crop species. The recent remarkable advances in understanding the functions and molecular mechanisms of the RALF-FER pathway have also raised many interesting questions that need to be answered in the future. This review mainly focuses on the roles of FER and other CrRLK1L members in modulating immune responses in the context of cell growth in response to their RALF peptide ligands and presents a brief outlook for future research.

Mutations of two FERONIA-like receptor genes enhance rice blast resistance without growth penalty.

Genes that provide resistance to fungi and/or bacteria usually reduce plant growth and ultimately affect grain yield. Thus, crop breeding programs need to find genetic resources that balance disease resistance with growth. The receptor kinase FERONIA regulates cell growth and survival in Arabidopsis. Here, we investigate, in rice, the role of members of the FERONIA-like receptor (FLR) gene family in the balance between growth and the response to the fungal pathogen Magnaporthe oryzae (Pyricularia oryzae), which causes the most devastating disease in rice. We carried out genome-wide gene expression and functional screenings in rice via a gene knockout strategy, and we successfully knocked out 14 FLR genes in rice. Using these genetic resources, we found that mutations in the FLR2 and FLR11 genes provide resistance to rice blast without a profound growth penalty. Detailed analyses revealed that FLR2 mutation increased both defense-related gene expression and M. oryzae-triggered production of reactive oxygen species. Thus, our results highlight novel genetic tools for studying the underlying molecular mechanisms of enhancing disease resistance without growth penalty.

Crystal-Growth-Dominated Fabrication of Metal-Organic Frameworks with Orderly Distributed Hierarchical Porosity.

Constructing architectures with hierarchical porosity has been widely considered as the most efficient way to bypass the problems related to slow mass transfer and inaccessibility of internal space in MOFs. Now, a crystal-growth-dominated strategy is proposed to fabricate hierarchically porous MOFs (HP-MOFs). When the crystal growth is dominated by the monomer attachment, the aggregation of nonionic surfactant or polymer can be easily captured and released during the crystal growth process, resulting in the formation and ordering hierarchical pores along the radial direction. Owing to the accelerated mass diffusion and more exposed active sites of this design, HP-MOFs exhibited an enhanced catalytic efficiency in styrene oxidation.

In Situ Template-Synthesis of Hollow CeO2 Nanobeads in scCO2 with Improved Catalytic Activity Towards CO Oxidation.

A green and robust route by in-situ generation of CeO2 beads around the carbon nanotubes (CNTs) in supercritical carbon dioxide (scCO2) was developed in this work to synthesize hollow CeO2 nanobeads with improved catalytic activity for CO oxidation.

A template-free method for stable CuO hollow microspheres fabricated from a metal organic framework (HKUST-1).

Uniform CuO hollow microspheres were successfully achieved from a non-uniform metal organic framework by using a template-free method. The process mechanism has been revealed to be spherical aggregation and Ostwald ripening. When tested in CO oxidation and heat treatment, these assembled microspheres exhibited an excellent catalytic performance and show a much better stability than the inherited hollow structure from MOFs.

Well-Dispersed and Size-Controlled Supported Metal Oxide Nanoparticles Derived from MOF Composites and Further Application in Catalysis.

Supported metal oxide nanoparticles are important in heterogeneous catalysis; however, the ability to tailor their size, structure, and dispersion remains a challenge. A strategy to achieve well-dispersed and size-controlled supported metal oxides through the manageable growth of a metal organic framework (Cu-BTC) on TiO2 followed by pyrolysis is described.

Carbon heterogeneous surface modification on a mesoporous TiO2-supported catalyst and its enhanced hydrodesulfurization performance.

In this work, we report a novel surface modification which can improve the desorption of a hydrodesulfurization product (H(2)S) from mesoporous TiO(2). The corresponding catalyst exhibits a significantly enhanced hydrodesulfurization performance compared with an unmodified catalyst, and the dibenzothiophene conversion increases from 65% to 98%.

A shortcut for evaluating activities of TiO2 facets: water dissociative chemisorption on TiO2-B (100) and (001).

By means of density functional theory (DFT) calculations, we study the water adsorption behavior on two common surfaces, (001) and (100) TiO(2)-B, which maintains the monoclinic structure as high as approximately 550 degrees C or higher in ambient conditions. The two surfaces show totally different activity for water dissociation. The dissociative chemisorption of water on TiO(2)-B (100) is identified at both submonolayer and monolayer coverages, which indicates considerable reactivity. In contrast, the non-dissociative molecular adsorption of water is the most stable state on TiO(2)-B (001) which suggests no special activity. Furthermore, we compare the structural features of different surfaces with diverse crystal structures, such as rutile, anatase, brookite, TiO(2)-B etc. Keeping a close eye on the exposed atoms on the surface, we conclude a more general criterion for a quick evaluation of reactivities of different TiO(2) surfaces merely based on local surface structure features.

Highly thermal stable and highly crystalline anatase TiO2 for photocatalysis.

In the absence of any doping and modification, the anatase-to-rutile phase transformation was inhibited at high temperatures giving rise to highly thermal stable and highly crystalline anatase TiO2 fibers. The initial formation of the TiO2(B) phase is found to be key in inhibiting this transformation. The intermediate structure of the TiO2 fiber comprises an inner anatase core with an outer TiO2(B) shell, which has a specific crystallographic orientation with respect to the anatase structure. During the calcination process from 300 to 800 degrees C, both the TiO2(B) shell and the bulk anatase crystal structure was preserved. At temperatures of 800-900 degrees C the TiO2(B)-to-anatase transformation was finished and a near-pure and thermally stable anatase fiber was obtained. This final product shows the same activity as a standard commercial photocatalyst Degussa P-25 when measured against unit mass, and 5 times the activity when measured with respect to the unit surface area. The anatase TiO2 fibers presented here have considerable interest as practical photocatalysts for water purification, as they can be easily recycled without a decrease in their photocatalytic activity and can be prepared at large scale and at low cost.

[Deactivation of titania whiskers used for purification of drinking water].

The reason of deactivation of titania whiskers used for deep purification of drinking water and the corresponding regeneration methods were presented. AFM, XRD and ICP were carried out to characterize the titanium dioxide. The experimental results suggest that the main reason of deactivation of titania whiskers is the deposition of calcium carbonate on the catalyst surface. The surface of titania whiskers is covered by the insoluble carbonates generated from carbon dioxide produced during the degradation of organics and metal ions such as calcium in the tap water, and the activity of the titania whiskers decreases gradually till deactivation. After washing by 1 mol/L hydrochloric acid for four hours, the photocatalytic activity of the titania whiskers can achieve 95 percent of that before deactivation. The photocatalytic activity of the titania whiskers which regenerated for many times keeps steady.

[Study on oxidant strengthening photocatalytic degradation of DMF over TiO2 fiber catalyst].

Oxidant strengthening the degradation of DMF aqueous solution was investigated when TiO2 fiber is used as the photocatalyst. When the UV light was absent, ozone per se could not make DMF degrade, which proves that DMF is a stable substance. But ozone could increase obviously photocatalytic degradation rate of DMF in O3/TiO2 (F). Under the same reaction condition, photocatalytic degradation rate and speed of DMF in O3/TiO2 (F) was almost 1.5 times and 2 times higher than that in air/ TiO2 (F) and H2O2/TiO2 (F) respectively. COD analysis showed DMF was almost mineralized completely when the reaction was carried out for 120 min. Through Hinsberg test secondary amine was proved as one of intermediates in the process of DMF photocatalytic degradation. Rise of pH value of reaction solution also showed that amine was produced in the photocatalytic reaction process. Degradation speed of DMA in O3/TiO2 (F) was higher than that in air/TiO2 (F). The increasing degradation rate and speed of DMF was mainly caused by fast degradation of secondary amine in the process of DMF photocatalytic degradation in O3/TiO2 (F).