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Heavy metal cadmium (Cd) at high concentrations severely disturbs plant growth and development. The E3 ubiquitin ligase involved in protein degradation is critical for plant tolerance to abiotic stress, but the role of E3 ubiquitin ligases in Cd tolerance is largely unknown in tomato. Here, we characterized an E3 ubiquitin ligase gene Sl1, which was highly expressed in roots under Cd stress in our previous study. The subcellular localization of Sl1 revealed that it was located in plasma membranes. In vitro ubiquitination assays confirmed that Sl1 had E3 ubiquitin ligase activity. Knockout of the Sl1 gene by CRISPR/Cas9 genome editing technology reduced while its overexpression increased Cd tolerance as reflected by the changes in the actual quantum efficiency of PSII photochemistry (ΦPSII) and hydrogen peroxide (H2O2) accumulation. Cd-induced increased activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were compromised in sl1 mutants but were enhanced in Sl1 overexpressing lines. Furthermore, the content of Cd in both shoots and roots increased in sl1 mutants while reduced in Sl1 overexpressing plants. Gene expression assays revealed that Sl1 regulated the transcript levels of heavy metal transport-related genes to inhibit Cd accumulation. These findings demonstrate that Sl1 plays a critical role in regulating Cd tolerance by relieving oxidative stress and resisting heavy metal transportation in tomato. The study provides a new understanding of the mechanism of plant tolerance to heavy metal stress.

The relationship between risk of glioma and alcohol consumption has been widely studied, but results have been conflicting. We therefore conducted a meta-analysis of observational studies to systematically assess the relationship between alcohol drinking and risk of glioma. Two electronic databases (PubMed and EMBASE) were searched from inception to 8 August 2013 to identify pertinent studies that linked alcohol drinking with glioma risk. We used a random-effects model to calculate the overall relative risk (RR) with corresponding 95% confidence intervals (CIs). Fifteen case-control and four cohort studies were identified for this analysis. The combined RR for total alcohol drinkers versus non-drinkers was 0.96 (95% CI: 0.89–1.04). In the subgroup analysis by geographic area, a significant association was observed in North American studies (RR = 0.78, 95% CI: 0.65–0.93), but not in European or Asian/Australian studies. In the subgroup analysis by study design, a borderline significant association emerged in population-based case-control studies (RR = 0.82, 95% CI: 0.68–0.99), but not in hospital-based case-control studies (RR = 1.00, 95% CI: 0.99–1.01) or cohort group (RR = 1.03, 95% CI: 0.88–1.20). Our results show no material association between alcohol consumption and risk of glioma existed. Further prospective evidences are needed to confirm this association.

Melatonin is a pleiotropic signal molecule that plays critical roles in regulating plant growth and development, as well as providing physiological protections against various environmental stresses. Nonetheless, the mechanisms for melatonin-mediated pollen thermotolerance remain largely unknown. In this study, we report that irrigation treatment with melatonin (20 µM) effectively ameliorated high temperature-induced inactivation of pollen and inhibition of pollen germination in tomato (Solanum lycopersicum) plants. Melatonin alleviated reactive oxygen species production in tomato anthers under high temperature by the up-regulation of the transcription and activities of several antioxidant enzymes. Transmission electron micrograph results showed that high temperature-induced pollen abortion is associated with a premature degeneration of the tapetum cells and the formation of defective pollen grains with degenerated nuclei at the early uninuclear microspore stage, whilst melatonin protected degradation of organelles by enhancing the expression of heat shock protein genes to refold unfolded proteins and the expression of autophagy-related genes and formation of autophagosomes to degrade denatured proteins. These findings suggest a novel function of melatonin to protect pollen activity under high temperature and support the potential effects of melatonin on reproductive development of plants.