Background information. Cadmium (Cd) is a highly toxic heavy metal that causes changes in plant metabolism through inhibiting photosynthesis and respiration. The effects of Cd on the morphology and function of the chloroplast and mitochondria, as well as on the production and localization of ROS (reactive oxygen species), were studied at the single-cell level in Arabidopsis.Results. The present study showed that the morphology of chloroplasts changed after Cd treatment, and the photochemical efficiency dramatically declined prior to obvious morphological distortion in the chloroplasts. A quick burst of ROS was detected after Cd treatment. The ROS appeared first in the mitochondria and subsequently in the chloroplast. Simultaneously, the mitochondria clumped irregularly around the chloroplasts or aggregated in the cytoplasm, and the movement of mitochondria was concomitantly blocked. Furthermore, the production of ROS was decreased after pre-treatment with ascorbic acid or catalase, which prevented inhibition of photosynthesis, organelle changes and subsequent protoplast death. Our results suggest that the distribution and mobility of mitochondria, the morphology of chloroplasts and the accumulation of ROS play important roles in Cd-induced cell death. The results are in good agreement with previous reports of many types of apoptotic-like cell death.Conclusion. The changes in the distribution and mobility of mitochondria, and morphology of chloroplasts, as well as the accumulation of ROS, play important roles in Cd-induced cell death.

Background: Golgi protein-73 (GP73) is a newly identified candidate serum marker for liver diseases. The utility of this biomarker remains limited, largely due to the lack of quantitative information. The aims of this study were to quantify serum GP73 (sGP73) in healthy individuals and in patients with liver diseases, and to validate sGP73 as a biomarker for early diagnosis of liver disease. Methods: Recombinant GP73 was used to generate monoclonal (mAb) and polyclonal antibodies ( pAb). Using these antibodies in a quantitative enzyme-linked immunosorbent assay, GP73 was measured in serum from 263 patients with various forms of liver and other diseases. Results: The median sGP73 in patients with liver disease was significantly higher (P , 0.001) than in healthy individuals and in patients with other diseases. When sGP73 was used to detect liver disease, it had a sensitivity of 82% and a specificity of 80% at the optimal cut-off value of 85.5 mg/L. The area under the receiver-operating characteristic curve was 0.9. Conclusion: sGP73 concentration in patients with liver disease was three-fold higher than in healthy individuals. However, sGP73 concentrations did not differ significantly between patients from each liver disease group. Furthermore, sGP73 was not significantly elevated in patients with diseases other than liver disease compared with healthy individuals. These results suggest that sGP73 may be used as a serum marker for the diagnosis of liver disease.

The present study compared the efficacy of standard and extended durations of PEG-IFNα-2a monotherapy for treatment of HBeAg-negative Chinese patients with chronic hepatitis B. Patients were randomized to receive standard therapy (n = 38; 48 weeks treatment) or extended therapy (n = 42; 72 weeks treatment). Extended therapy resulted in a significantly higher HBV DNA inhibition at 24 and 48 weeks after the end of treatment, a significantly higher sustained HBV DNA inhibition at the end of treatment, and a significantly lower HBsAg level at 24 and 48 weeks after the end of treatment (P < 0.05 for all comparisons). The HBsAg clearance rate was significantly greater in the extended therapy group than in the standard therapy group at 24 and 48 weeks post-treatment (33.3% vs. 10.5% and 35.7% vs. 10.5%, respectively; P < 0.05 for both). In addition, patients with an increase of more than 1 log10  IU/ml in HBsAg level from baseline to week 24 had a significantly lower level of HBsAg at end of treatment (0.54 ± 1.76 vs. 2.89 ± 1.27, P < 0.001), but a higher level of HBsAg clearance (64.3% vs. 7.6%, P < 0.001). Assessment of HBsAg level at week 24 appears to be a suitable checkpoint. These results indicate that 72 weeks of PEG-IFNα-2a monotherapy benefits HBeAg-negative Chinese patients with chronic hepatitis B who are infected with HBV genotype B or C.

BackgroundChlorosis of leaf tissue normally observed during pathogen infection may result from the degradation of chloroplasts. There is a growing evidence to suggest that the chloroplast plays a significant role during pathogen infection. Although most degradation of the organelles and cellular structures in plants is mediated by autophagy, its role in chloroplast catabolism during pathogen infection is largely unknown.ResultsIn this study, we investigated the function of autophagy in chloroplast degradation during avirulent Pst DC3000 (AvrRps4) infection. We examined the expression of defensive marker genes and suppression of bacterial growth using the electrolyte leakage assay in normal light (N) and low light (L) growing environments of wild-type and atg5-1 plants during pathogen treatment. Stroma-targeted GFP proteins (CT-GFP) were observed with LysoTracker Red (LTR) staining of autophagosome-like structures in the vacuole. The results showed that Arabidopsis expressed a significant number of small GFP-labeled bodies when infected with avirulent Pst DC3000 (AvrRps4). While barely detectable, there were small GFP-labeled bodies in plants with the CT-GFP expressing atg5-1 mutation. The results showed that chloroplast degradation depends on autophagy and this may play an important role in inhibiting pathogen growth.ConclusionAutophagy plays a role in chloroplast degradation in Arabidopsis during avirulent Pst DC3000 (AvrRps4) infection. Autophagy dependent chloroplast degradation may be the primary source of reactive oxygen species (ROS) as well as the pathogen-response signaling molecules that induce the defense response.

As a widespread pollutant in the environment, cadmium (Cd) would be accumulated in leaves and cause phytotoxic effect on plants. Salicylic acid (SA), a natural signal molecule, plays an important role in eliciting specific responses to biotic and abiotic stresses. In our case, the effect of SA on Cd-induced photochemical damage and cell death in Arabidopsis was studied. The results illustrated that Cd could cause a series of physiological events such as chloroplast structure change (e.g. irregular mesophyll cell as well as ultrastructure change), reactive oxygen species (ROS) production and cell death. Furthermore, chlorophyll fluorescence parameters (F(v)/F(m), qN and ETR) showed a rapid decrease in wild-type (WT) Arabidopsis after treatment with 50 μM CdCl(2), identical with the change in chlorophyll delayed fluorescence (DF) intensity. The changes of these parameters showed the damage of Cd toxicity to photosynthetic apparatus. We found that cell death might be autophagic cell death, which might be caused by Cd toxicity induced oxidative stress just like photosynthetic damage. The NahG plants with lower SA accumulation level showed more sensitivity to Cd toxicity, although they exhibited a decrease both in chlorophyll fluorescence parameters and DF intensity. Exogenously SA prevented the Cd-induced photochemical efficiency decrease and mitigated Cd toxicity. Additionally, SA pretreatment could alleviate Cd-induced ROS overproduction. In conclusion, our results suggested that SA could prevent Cd-induced photosynthetic damage and cell death, which might be due to the inhibition of ROS overproduction.

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Using a highly sensitive single photon counter, a spontaneous chemiluminescence (CL) study on rice (Oryza sativa L.) seeds stored in different years was carried out. We first observed that the degree of ageing in rice seeds was related to the intensity of spontaneous CL during early imbibition (0-30 min). Rice seeds stored for a shorter time had a stronger intensity of CL in early imbibition. The germination rate of rice seeds showed an obvious positive correlation with the intensity of spontaneous CL. Singlet oxygen ((1)O(2)) in rice seeds during early imbibition was investigated by a CL method using a cypridina luciferin analogue, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo [1,2alpha] pyrazin-3-one (MCLA), as a selective CL probe. Additional experimental evidence for the formation of (1)O(2) came from the quenching effect of sodium azide (NaN(3)) on MCLA-mediated rice seeds' CL. Analysis based on the experimental results demonstrated that spontaneous CL in rice seeds during early imbibition was mainly contributed by singlet oxygen ((1)O(2)).

The phytohormone abscisic acid (ABA) plays critical roles in abiotic stress responses and plant development. In germinating seeds, the phytochrome-associated protein phosphatase, FyPP3, negatively regulates ABA signaling by dephosphorylating the transcription factor ABI5. However, whether and how FyPP3 is regulated at the posttranscriptional level remains unclear. Here, we report that an asparagine-rich protein, NRP, interacts with FyPP3 and tethers FyPP3 to SYP41/61-positive endosomes for subsequent degradation in the vacuole. Upon ABA treatment, the expression of NRP was induced and NRP-mediated FyPP3 turnover was accelerated. Consistently, ABA-induced FyPP3 turnover was abolished in an nrp null mutant. On the other hand, FyPP3 can dephosphorylate NRP in vitro, and overexpression of FyPP3 reduced the half-life of NRP in vivo. Genetic analyses showed that NRP has a positive role in ABA-mediated seed germination and gene expression, and that NRP is epistatic to FyPP3. Taken together, our results identify a new regulatory circuit in the ABA signaling network, which links the intracellular trafficking with ABA signaling.