Dynamic intracellular reorganization of cytoskeletons and the vacuole in defense responses and hypersensitive cell death in plants

Plants have evolved various means for controlled and organized cell destruction, known as programmed cell death (PCD). In plant immune responses against microbial infection, hypersensitive cell death as a form of PCD is a crucial event to prevent the spread of biotrophic pathogens. Recent live cell imaging techniques have revealed dynamic features and significant roles of cytoskeletons and the vacuole during defense responses and the PCD. Actin microfilaments (MFs) focus on the infection sites and function as tracks for the polar transport of antimicrobial materials. To accomplish hypersensitive cell death, further dynamic changes in cytoskeletons are induced. MFs play a role in the structural and functional regulation of the vacuole, leading to execution of the PCD. We here overview spatiotemporal dynamic changes in the cytoskeletons and the vacuoles triggered by signals from pathogens, and propose a hypothetical model for MF-regulated vacuole-mediated PCD in plant immunity.     

Non-acidic compounds induce the intense sweet taste of neoculin, a taste-modifying protein

Neoculin, a sweet protein found in the fruit of Curculigo latifolia, has the ability to change sourness into sweetness. Neoculin turns drinking water sweet, indicating that non-acidic compounds may induce the sweetness. We report that ammonium chloride and certain amino acids elicit the intense sweetness of neoculin. Neoculin can thus sweeten amino acid-enriched foods.     

Total and high molecular weight adiponectin and hepatocellular carcinoma with HCV infection

Background

Adiponectin is shown to be inversely associated with development and progression of various cancers. We evaluated whether adiponectin level was associated with the prevalence and histological grade of hepatocellular carcinoma (HCC), and liver fibrosis in patients with hepatitis C virus (HCV) infection.

Methods

A case-control study was conducted on 97 HCC patients (cases) and 97 patients (controls) matched for sex, Child-Pugh grade and platelet count in patients with HCV infection. The serum total and high molecular weight (HMW) adiponectin levels were measured by enzyme-linked immunosorbent assays and examined in their association with the prevalence of HCC. In addition, the relationship between these adiponectin levels and body mass index (BMI), progression of liver fibrosis, and histological grade of HCC was also evaluated. Liver fibrosis was assessed using the aspartate aminotransferase to platelet ratio index (APRI).

Results

There were no significant differences in the serum total and HMW adiponectin levels between cases and controls. Moreover, there were no inverse associations between serum total and HMW adiponectin levels and BMI in both cases and controls. On the other hand, serum total and HMW adiponectin levels are positively correlated with APRI in both cases (r = 0.491, P<0.001 and r = 0.485, P<0.001, respectively) and controls (r = 0.482, P<0.001 and r = 0.476, P<0.001, respectively). Interestingly, lower serum total (OR 11.76, 95% CI: 2.97–46.66 [P<0.001]) and HMW (OR 10.24, CI: 2.80–37.40 [P<0.001] adiponectin levels were independent risk factors of worse histological grade of HCC.

Conclusions

Our results suggested that serum total and HMW adiponectin levels were predictors of liver fibrosis, but not prevalence of HCC in patients with HCV infection. Moreover, low these adiponectin levels were significantly associated with worse histological grades.     

Induction and monitoring of definitive and visceral endoderm differentiation of mouse ES cells

Preparation of specific lineages at high purities from embryonic stem (ES) cells requires both selective culture conditions and markers to guide and monitor the differentiation. In this study, we distinguished definitive and visceral endoderm by using a mouse ES cell line that bears the gfp and human IL2R alpha (also known as CD25) marker genes in the goosecoid (Gsc) and Sox17 loci, respectively. This cell line allowed us to monitor the generation of Gsc+ Sox17+ definitive endoderm and Gsc- Sox17+ visceral endoderm and to define culture conditions that differentially induce definitive and visceral endoderm. By comparing the gene expression profiles of definitive and visceral endoderm, we identified seven surface molecules that are expressed differentially in the two populations. One of the seven markers, Cxcr4, to which a monoclonal antibody is available allowed us to monitor and purify the Gsc+ population from genetically unmanipulated ES cells under the condition that selects definitive endoderm.     

The RNA binding protein TLS is translocated to dendritic spines by mGluR5 activation and regulates spine morphology

Neuronal dendrites, together with dendritic spines, exhibit enormously diverse structure. Selective targeting and local translation of mRNAs in dendritic spines have been implicated in synapse remodeling or synaptic plasticity. The mechanism of mRNA transport to the postsynaptic site is a fundamental question in local dendritic translation. TLS (translocated in liposarcoma), previously identified as a component of hnRNP complexes, unexpectedly showed somatodendritic localization in mature hippocampal pyramidal neurons. In the present study, TLS was translocated to dendrites and was recruited to dendrites not only via microtubules but also via actin filaments. In mature hippocampal pyramidal neurons, TLS accumulated in the spines at excitatory postsynapses upon mGluR5 activation, which was accompanied by an increased RNA content in dendrites. Consistent with the in vitro studies, TLS-null hippocampal pyramidal neurons exhibited abnormal spine morphology and lower spine density. Our results indicate that TLS participates in mRNA sorting to the dendritic spines induced by mGluR5 activation and regulates spine morphology to stabilize the synaptic structure.     

Polymorphisms of TNFalpha, IL1beta, and IL1RN genes in chronic obstructive pulmonary disease

It is recognized that genetic factors play a role in the susceptibility to COPD. COPD is characterized by airflow limitation. Chronic inflammation causes small airway disease and parenchymal destruction, leading to the airflow limitation. Polymorphisms in pro-inflammatory cytokine genes may confer a risk for the development of COPD. A case-control association study was performed in Japanese population (88 COPD patients and 61 controls) and Egyptian population (106 patients and 72 controls). Genotype and allele frequencies of the TNFalpha -308 G/A and +489 G/A polymorphisms, the IL1beta -511 C/T, -31 T/C, and +3954 C/T polymorphisms, and a VNTR polymorphism in intron 2 of the IL1RN gene were investigated. In addition, pairwise haplotype frequencies were analyzed. When studied independently, none of the polymorphisms were associated with the development of COPD in both populations. However, in the Egyptian population, the distributions of the haplotype (IL1beta -31 T/C : IL1beta +3954 C/T) were significantly different between the COPD patients and the controls (p(corr)=0.0037). Our findings suggest that this haplotype within the IL1beta gene may be involved in the pathogenesis of COPD and that the genetic factors of COPD susceptibility might be different between different populations.     

Fourier transform infrared spectrum of the secondary quinone electron acceptor Q(B) in photosystem II

Fourier transform infrared difference spectra upon single reduction of the secondary quinone electron acceptor Q(B) in photosystem II (PSII), without a contribution from the electron donor-side signals, were obtained for the first time using Mn-depleted PSII core complexes of the thermophilic cyanobacterium Thermosynechococcus elongatus. The Q(B)(-)/Q(B) difference spectrum exhibited a strong C...O stretching band of the semiquinone anion at 1480 cm(-)(1), the frequency higher by 2 cm(-)(1) than that of the corresponding band of Q(A)(-), in agreement with the previous S(2)Q(B)(-)/S(1)Q(B) spectrum of the PSII membranes of spinach [Zhang, H., Fischer, G., and Wydrzynski, T. (1998) Biochemistry 37, 5511-5517]. Also, several peaks originating from the Fermi resonance of coupled His modes with its strongly H-bonded NH vibration were observed in the 2900-2600 cm(-)(1) region, where the peak frequencies were higher by 7-24 cm(-)(1) compared with those of the Q(A)(-)/Q(A) spectrum. These frequency differences suggest that H-bond interactions of the CO groups, especially with a His side chain, are different between Q(B)(-) and Q(A)(-). Furthermore, a prominent positive peak was observed at 1745 cm(-)(1) in the C=O stretching region of COOH or ester groups in the Q(B)(-)/Q(B) spectrum. The peak frequency was unaffected by D(2)O substitution, indicating that this peak does not arise from a COOH group but probably from the 10a-ester C=O group of the pheophytin molecule adjacent to Q(B). The absence of protonation of carboxylic amino acids upon Q(B)(-) formation in contrast to the previous observation in the purple bacterium Rhodobacter sphaeroides suggests that the protonation mechanism of Q(B) in PSII is different from that of bacterial reaction centers.     

Density functional theory calculations on the dielectric constant dependence of the oxidation potential of chlorophyll: implication for the high potential of P680 in photosystem II

The primary donor chlorophyll (Chl) of photosystem II (PSII), P680, has an extremely high oxidation redox potential (E(ox)) of approximately 1.2 V, which is essential for photosynthetic water oxidation. The mechanism for achieving a high potential such as that of P680 has been one of the central questions in photosynthesis research. Here, we have examined the dielectric constant (epsilon) dependence of the E(ox) of monomer Chl using density functional theory calculations with the polarizable continuum model. The calculated E(ox) of a model Chl compound exhibited a sharp increase with a decrease in epsilon in the relatively low epsilon region (epsilon < 5). In contrast, in the higher-epsilon region, E(ox) was rather insensitive to epsilon and converged to a constant value at very high epsilon values. This tendency in the high-epsilon region explains the experimental E(ox) values of isolated Chl a that have been observed in a relatively narrow range of 0.74-0.93 V. The E(ox) of Chl in an ideal hydrophobic protein was estimated to be approximately 1.4 V at an epsilon value of 2. This value indicates that Chl in a hydrophobic environment originally has a high E(ox) that is sufficient for oxidizing water (E(ox) = 0.88 V at pH 6). On the basis of the reported X-ray crystallographic structures, the protein environment of P680 in PSII was estimated to be more hydrophobic than that of the primary donors in bacterial reaction centers. It is therefore suggested that the low-dielectric environment around P680 is one of the major factors in its very high E(ox), and thus, introducing nonpolar amino acids into the binding pocket of P680 was an important process in the evolution of PSII.