Knockout of SlYTH2, encoding a YTH domain-containing protein, caused plant dwarfing, delayed fruit internal ripening, and increased seed abortion rate in tomato

The m6A is one of the most abundant and widespread modifications in eukaryotic mRNAs, which regulates gene expression at the post-transcriptional level and plays key roles in many physiological processes. The YT521-B homologous (YTH) domain-containing proteins act as m6A readers to regulate m6A-RNA metabolism processes and mediate the various functions of m6A modification. Previously, we reported tomato contains 9 YTH genes, among which SlYTH2 is relatively highly expressed. This study reports the physiological functions of SlYTH2 in tomato. SlYTH2 protein is distributed in the nucleus and cytoplasm, and its three-dimensional structure is highly similar to human HsYTHDF1. SlYTH2 knockout through Crispr/Cas9 gene editing technology leaded to pleiotropic phenotypes, including dwarfing plant, delayed fruit internal ripening process, and increased seed abortion rate. The deletion of SlYTH2 gene increased the accumulation of endogenous ABA, decreased the content of endogenous GA3, and enhanced the sensitivity of seed germination to exogenous ABA and seedling growth to exogenous GA3. RNA-Seq data showed that the expression levels of multiple hormone-related genes were altered in SlYTH2 knockout line. These facts suggested SlYTH2 plays its physiological roles related to ABA, gibberellin and other hormones in tomato.

Tomato SlYTH1 encoding a putative RNA m6A reader affects plant growth and fruit shape

N⁶-methyladenosine (m⁶A), the most abundant and common modification on eukaryotic mRNA, plays crucial roles in multiple biological processes through controlling endogenous gene activity in organisms. The m⁶A reader specifically recognizes the m⁶A mark to mediate the regulation of m⁶A on mRNA, and determines the fate of its target mRNA. In plants, the currently confirmed m⁶A readers are YTH (YT521B homology) domain-containing proteins. We previously reported that tomato contains 9 YTH genes, of which SlYTH1 has the strongest expression. The present study reports the functional characterization of SlYTH1 in tomato. SlYTH1 mutants generated via CRISPR/Cas9 technology exhibited pleiotropic phenotypes, including low seed germination rate, shortened seedling root, retarded plant growth and development during vegetative development, and elongated and longitudinally flattened fruit with reduced the locule number. SlYTH1 knockout reduced GA₃ content and downregulated the expression of related genes in gibberellin biosynthesis pathway. Moreover, exogenous GA₃ application could partially restore the phenotypic defects caused by SlYTH1 mutations. SlYTH1 knockout could alleviate the inhibition of seedling root elongation by exogenous GA₃ application at relatively low concentration. These facts indicated SlYTH1 is involved in regulating gibberellin biosynthesis and plays important roles in multiple physiological processes in tomato.

Genome-wide identification and characterization of YTH domain-containing genes, encoding the m6A readers, and their expression in tomato

9 YTH genes in tomato were identified and cloned, and their expression patterns were comprehensively analyzed, which reveal potential multiple roles in development and fruit ripening. N⁶-methyladenosine (m⁶A) is an abundant and pervasive post-transcriptional modification in eukaryotic mRNAs. The YTH domain-containing proteins act as m⁶A readers to read m⁶A marks and transduce their downstream regulatory effects by altering m⁶A-mRNA metabolism processes. Identification of YTH proteins is essential for understanding the regulatory mechanisms of m⁶A in physiological processes, but little is known about YTH proteins in tomato, a model system for fruit development. Here, we report that tomato genomes contain a total of 9 SlYTH genes. While YTH proteins of both tomato and Arabidopsis can be classified into two subfamilies, the member distributions in subfamilies are very different between the two species. Homology modeling exhibited the similar three-dimensional structures of SlYTH proteins to human YTHDF1 or YTHDC1. Multiple hormone-response elements locating on the promoters of SlYTH genes indicate that they are involved in the physiological processes related to phytohormone. SlYTH genes are ubiquitous and spatiotemporal dynamic expression in tomato. Eight SlTYH genes have the strongest expression in stamens among the parts of flowers. Throughout fruit ontogeny, most of the SlYTH genes display obvious high mRNA levels during the developmental phases (4 dpa to mature green); moreover, SlYTH1 and SlYTH2 have absolute predominant expressions demonstrated by RNA-seq. The results lay a foundation for future characterizations on the functions of YTH proteins and m⁶A regulatory mechanism in tomato.

Schwann-like cell differentiation of rat adipose-derived stem cells by indirect co-culture with Schwann cells in vitro

OBJECTIVES

Schwann cell (SC) transplantation is a promising therapy for peripheral nerve transaction, however, clinical use of SCs is limited due to their very limited availability. Adipose-derived stem cells (ADSCs) have been identified as an alternative source of adult stem cells in recent years. The aim of this study was to evaluate the feasibility of using ADSCs as a source of stem cells for differentiation into Schwann-like cells by an indirect co-culture approach, in vitro.

MATERIALS AND METHODS

Multilineage differentiation potential of the obtained ADSCs was assayed by testing their ability to differentiate into osteoblasts and adipocytes. The ADSCs were co-cultured with SCs to be induced into Schwann-like cells through proximity, using a Millicell system. Expression of typical SC markers S-100, GFAP and P75NTR of the treated ADSCs was determined by immunocytochemical staining, western blotting and RT-PCR. Myelination capacity of the differentiated ADSCs (dADSCs) was evaluated in dADSC/dorsal root ganglia neuron (DRGN) co-cultures.

RESULTS

The treated ADSCs adopted a spindle shaped-like morphology after co-cultured with SCs for 6 days. All results of immunocytochemical staining, western blotting and RT-PCR showed that the treated cells expressed S-100, GFAP and P75NTR, indications of differentiation. dADSCs could form Schwann-like cell myelin in co-culture with DRGNs. Undifferentiated ADSCs (uADSCs) did not form myelin compared to DRGNs cultured alone, but could produce neurite extension.

CONCLUSIONS

These results demonstrate that this indirect co-culture microenvironment could induce ADSCs to differentiate into Schwann-like cells in vitro, which may be beneficial for treatment of peripheral nerve injuries in the near future.

Protective role of tretinoin and N-acetyl-L-cysteine from antiproliferative action of cigarette smoke extract on alveolar epithelial cells

To investigate the mechanisms by which tretinoin and N-acetyl-L-cysteine (NAC) reverse the growth inhibition of alveolar epithelial cells induced by cigarette smoke extract (CSE), MTT assay was used to evaluate cell viability. It was observed that both tretinoin and NAC could restore the viability of CSE-inhibited A549 cells. By incubation with fluorescent indicator H2DCFDA, it was documented that CSE-stimulated accumulation of intracellular reactive oxygen species (ROS) was obviously decreased by tretinoin or NAC. Furthermore, using semi-quantitative and real-time quantitative RT-PCR as well as western blot methods, high expression of insulin-like growth factor binding protein-2 (IGFBP-2) in A549 cells treated with CSE was found at both transcriptional and protein levels, and concomitant with the restoration of cell growth after treatment with tretinoin or NAC, down regulation of IGFBP-2 was observed. From the present study, it is concluded that both RA and NAC can antagonize CSE-induced growth arrest of alveolar epithelial cells and that down regulation of IGFBP-2 may play an important role in the process.

Combined transplantation of neural stem cells and olfactory ensheathing cells for the repair of spinal cord injuries

Spinal cord repair is a problem that has long puzzled neuroscientists. The failure of the spinal cord to regenerate and undergo reconstruction after spinal cord injury (SCI) can be attributed to secondary axonal demyelination and neuronal death followed by cyst formation and infarction as well as to the nature of the injury environment, which promotes glial scar formation. Cellular replacement and axon guidance are both necessary for SCI repair. Multipotent neural stem cells (NSCs) have the potential to differentiate into both neuronal and glial cells and are, therefore, likely candidates for cell replacement therapy following SCI. However, NSC transplantation alone is not sufficient for spinal cord repair because the majority of the NSCs engrafted into the spinal cord have been shown to differentiate with a phenotype which is restricted to glial lineages, further promoting glial scaring. Olfactory ensheathing cells (OECs) are a unique type of glial cell that occur both peripherally and centrally along the olfactory nerve. The ability of olfactory neurons to grow axons in the mature central nervous system (CNS) milieu has been attributed to the presence of OECs. It has been shown that transplanted OECs are capable of migrating into and through astrocytic scars and thereby facilitating axonal regrowth through an injury barrier. Given the complementary properties of NSCs and OECs, we predict that the co-transplantation of NSCs and OECs into an injured spinal cord would have a synergistic effect, promoting neural regeneration and functional reconstruction. The lost neurocytes would be replaced by NSCs, while the OECs would build "bridges" crossing the glial scaring that conduct axon elongation and promote myelinization simultaneously. Furthermore, the two types of cells could first be seeded into a bioactive scaffold and then the cell seeded construct could be implanted into the defect site. We believe that this type of treatment would lead to improved neural regeneration and functional reconstruction after SCI.

Protective effects of extract of Ginkgo biloba (EGb 761) on nerve cells after spinal cord injury in rats

STUDY DESIGN

An experimental animal model was used to assess spinal cord injury following lateral hemitransection at thoracic spinal cord level.

OBJECTIVE

To determine whether extract of Ginkgo biloba (EGb) could have a neuroprotective effect in spinal cord injury (SCI) in rats.

SETTING

Department of Biological Sciences and Biotechnology, Tsinghua University, China.

METHODS

A total of 72 adult rats were divided randomly into three groups: the EGb group, normal saline (NS) group, and sham operation group (sham group). After thoracic spinal cord hemitransection was performed at the level of the 9th thoracic vertebra (T9), rats in the EGb group were given 100 mg/kg EGb 761 daily, while rats in the NS group received NS. The rats in the sham group only underwent laminectomy without spinal cord hemitransection. At various time points after surgery, thoracic spinal cords were sampled and sliced for histochemistry, immunohistochemistry of inducible nitric oxide synthase (iNOS), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) of apoptotic cells.

RESULTS

Myelin staining showed that the area of cavities was small and the demyelinated zones were limited at and around the injury site of the spinal cord in the EGb group, while the area of cavities was large and the demyelinated zones were serious in the NS group. Nissl staining showed that the ratio of bilateral ventral horn neurons (transection side/uninjured side) in the EGb group was higher than that in the NS group (P<0.05). The apoptotic index and the percentage of iNOS-positive cells were lower in the EGb group than in the NS group. Furthermore, the percentage of iNOS-positive cells positively correlated with the apoptotic index (r( 2)=0.729, P<0.01) after SCI.

CONCLUSION

This study demonstrated that EGb 761 could inhibit iNOS expression and have neuroprotective effect by preventing nerve cells from apoptosis after SCI in rats.

Development of the specific purpose Monte Carlo code CEARXRF for the design and use of in vivo X-ray fluorescence analysis systems for lead in bone

X-ray fluorescence (XRF) systems have been increasingly used for in vivo toxic trace-element analysis in the human body, such as lead in the tibia. Monte Carlo simulation can provide an efficient and flexible method for designing and using in vivo XRF systems. The Monte Carlo code CEARXRF has been developed specifically to simulate the complete pulse height spectrum of energy-dispersive XRF systems. This code is capable of tracking photons in a general geometry and modelling all of the physics of photon interactions in the energy range 1-150 keV for elements Z = 1-94, including primary and higher degree excitations of K and L XRF, the Doppler broadening of Compton-scattered photon energies, and the polarization effects in low-energy photon scatterings. The scattering background for minimum detectable concentration (MDC) analysis may be simulated more accurately by taking into account Doppler broadening in the distribution of the Compton-scattered photon energy due to electron-binding effects. The use of polarized excitation photons has been shown to be important in producing a low scattering background and good measurement sensitivity. The code has two very unique and important features: (1) complete composition and density correlated sampling that is extremely useful for studying measurement sensitivity to small changes in sample composition and density; and (2) Monte Carlo library spectra calculation for the determination of elemental amounts by the Monte Carlo-Library Least-Squares (MCLLS) method. The capability of CEARXRF to aid the design and optimization of in vivo XRF analysis has been verified by modelling hypothesized lead K and L XRF measurement systems.

Optimization of in vivo X-ray fluorescence analysis methods for bone lead by simulation with the Monte Carlo code CEARXRF

In the design of X-ray fluorescence (XRF) systems for in vivo measurements of lead in human bone, the most important considerations are the minimum detectable concentration (MDC), and accuracy and precision. Possible design optimizations can be investigated much more easily and economically by Monte Carlo simulation than by experiment. The specific purpose Monte Carlo code CEARXRF has been used in the present study for: (1) improving the MDC of a hypothesized in vivo 109Cd source-based KXRF system and a 109Cd source or X-ray tube source-based LXRF system by investigating the effects of source polarization and source-bone-detector geometry modification on reducing the scattering background, and (2) investigating the effects of sample variables, such as overlying skin thickness on the MDC and the lead XRF intensity precision. In addition, the feasibility of the Monte Carlo-Library Least-Squares (MCLLS) approach has been investigated in a preliminary fashion for 109Cd-based KXRF spectroscopy analysis.

Black box radiation gauges and analyzers: dream or reality?

This paper describes our attempts to make radiation gauges and analyzers operate in more of a 'black box' manner-being more independent of or at least more insensitive to changes in such things as sample composition and position. Our overall approach relies heavily on Monte Carlo simulation and that is discussed first in relation to radiation gauge and analyzer design and usage. Then the principles and applications of radiation gauges and analyzers including the Measurement Chi-Square and Monte Carlo Library Least-Squares, respectively, are treated. Finally, future work in this area is discussed.