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Tobacco mosaic virus (TMV) is one of the most damaging plant viruses from an economic and research point of view. Epigallocatechin-3-Gallate (EGCG), a flavonoid type secondary metabolite can selectively improve plant defense against pathogens; however, the effect of EGCG on plant defense against TMV and the underlying mechanism(s) remain elusive. In this study, exogenous EGCG application increased plant resistance to TMV as revealed by significantly decreased transcript levels of TMV-coat protein (CP) in tomato leaves. A time-course of H2O2 concentrations in tomato leaves showed that TMV inoculation rapidly increased the H2O2 accumulation, reaching its peak at 3 days post-inoculation (dpi) which remained the highest until 6 dpi. However, the combined treatment of EGCG and TMV remarkably decreased the concentrations of H2O2 at 3 and 6 dpi. Meanwhile, the transcript levels of RESPIRATORY BURST OXIDASE HOMOLOG 1 (SlRBOH1) were significantly increased by either EGCG or TMV inoculation, but the EGCG treatment along with TMV caused a further upregulation in the SlRBOH1 transcripts compared with that in only TMV-inoculated plants. Chemical scavenging of H2O2 or silencing SlRBOH1 both compromised the EGCG-induced enhanced resistance to TMV. Furthermore, EGCG-induced elevation in the activity of antioxidant enzymes was abolished by SlRBOH1 silencing, suggesting that EGCG enhanced defense against TMV by increasing the antioxidant enzyme activity via RBOH1-dependent H2O2 signaling. Taken together, our results suggest that EGCG functioned to maintain a delicate balance between ROS signaling and ROS scavenging via RBOH1, which enhanced tomato resistance to TMV.

The effect of particle morphology on denitrification performance in element sulfur-based denitrification (ESDeN) packed-bed process is a gap. In this study, three different types of commercial sulfur particles were selected to build the ESDeN reactors. The results showed the reactors filled with rougher sulfur particles took shorter time to reach stable denitrification performance in the start-up stage. The reactors filled with cap-shape sulfur particles received the maximum nitrate removal rate of 849.49 ± 79.29 g N m

This study was carried out to determine the effect of influent nitrate loading on nitrite accumulation during elemental-sulfur based denitrification process, and proposed to enhance the nitrogen removal efficiency by mitigating nitrite accumulation with thiosulfate as external electron donor. Along with increasing the nitrate influent loading (from 0.09 kg N/m3/d to 1.73 kg N/m3/d) by shortening the empty bed contact time (EBCT) (from 5 h to 0.25 h), the nitrate removal loading increased from 0.08 to 0.83 kg N/m3/d. Meanwhile, the raise of the nitrate influent loading obviously aggravated the nitrite accumulation. Herein, nitrite began to accumulate since the nitrate influent loading was over 0.86 kg N/m3/d, and a maximum nitrite accumulation of 2.39 mg/L was observed under the 0.25 h of EBCT and 15 mg/L of nitrate influent concentration condition. Thiosulfate was used as the external electron donor to accelerate the nitrite reduction rate in order to mitigate the nitrite accumulation. As a result, the nitrite accumulation significantly decreased from 2.39 mg/L to 0.17 mg/L with the thiosulfate dosage of 13.36 mg/L. However, the nitrite accumulation bounced with the on-going increase of the thiosulfate dosage, indicating that the nitrate reduction rate and nitrite reduction rate were accelerated alternatively. After dosing thiosulfate, the relative abundances of sulfurimonas and ferritrophicum grew up significantly.

Arsenic is a toxic metalloid for both animals and plants. The signaling molecule melatonin can enhance abiotic stress tolerance, but the effects of As and melatonin on tea plants and the mechanisms of resilience remain unclear. Here we report that excess As causes severe oxidative stress in tea leaves as revealed by significantly reduced maximal photochemical efficiency of photosystem-II, and increased reactive oxygen species accumulation and lipid peroxidation. However, exogenous melatonin application alleviated the As phytotoxicity and increased the anthocyanin content upto 69.4 % by selectively upregulating the expression of its biosynthetic genes such as CsCHS and CsANS. Comparison of As tolerance between two tea genotypes differing in basal levels of anthocyanin revealed that a tea cultivar with increased anthocyanin content, Zijuan (ZJ), showed enhanced tolerance to As stress compared with Longjing 43 (LJ43) that contained relatively low levels of anthocyanin. Interestingly, exogenous anthocyanin also enhanced As tolerance in LJ43, but exogenous melatonin did not improve As tolerance in ZJ genotype. Analysis of As content in tea leaves revealed that melatonin significantly reduced As content in LJ43 but not in ZJ, suggesting that melatonin-enhanced tolerance to As stress is largely dependent on the basal levels of anthocyanin in tea plants.