ZmGns, a maize class I ß-1,3-glucanase, is induced by biotic stresses and possesses strong antimicrobial activity.

Plant ß-1,3-glucanases are members of the pathogenesis-related protein 2 (PR-2) family, which is one of the 17 PR protein families and plays important roles in biotic and abiotic stress responses. One of the differentially expressed proteins (spot 842) identified in a recent proteomic comparison between five pairs of closely related maize (Zea mays L.) lines differing in aflatoxin resistance was further investigated in the present study. Here, the corresponding cDNA was cloned from maize and designated as ZmGns. ZmGns encodes a protein of 338 amino acids containing a potential signal peptide. The expression of ZmGns was detectible in all tissues studied with the highest level in silks. ZmGns was significantly induced by biotic stresses including three bacteria and the fungus Aspergillus flavus. ZmGns was also induced by most abiotic stresses tested and growth hormones including salicylic acid. In vivo, ZmGns showed a significant inhibitory activity against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and fungal pathogen Botrytis cinerea when it overexpressed in Arabidopsis. Its high level of expression in the silk tissue and its induced expression by phytohormone treatment, as well as by bacterial and fungal infections, suggest it plays a complex role in maize growth, development, and defense.

Hydrogen Sulfide Inhibits High Glucose-Induced Neuronal Senescence by Improving Autophagic Flux via Up-regulation of SIRT1.

Hyperglycemia, a key characteristic and risk factor for diabetes mellitus (DM), causes neuronal senescence. Hydrogen sulfide (H2S) is a novel neuroprotectant. The present work was to investigate the potential effect of H2S on hyperglycemia-induced neuronal senescence and the underlying mechanisms. We found that NaHS, a donor of H2S, inhibited high glucose (HG)-induced cellular senescence in HT22 cells (an immortalized mouse hippocampal cell line), as evidenced by a decrease in the number of senescence associated-ß-galactosidase (SA-ß-gal) positive cells, increase in the growth of cells, and down-regulations of senescence mark proteins, p16INK4a and p21CIP1. NaHS improved the autophagic flux, which is judged by a decrease in the amount of intracellular autophagosome as well as up-regulations of LC3II/I and P62 in HG-exposed HT22 cells. Furthermore, blocked autophagic flux by chloroquine (CQ) significantly abolished NaHS-exerted improvement in the autophagic flux and suppression in the cellular senescence of GH-exposed HT22 cells, which indicated that H2S antagonizes HG-induced neuronal senescence by promoting autophagic flux. We also found that NaHS up-regulated the expression of silent mating type information regulation 2 homolog 1 (SIRT1), an important anti-aging protein, in HG-exposed HT22 cells. Furthermore, inhibition of SIRT1 by sirtinol reversed the protection of H2S against HG-induced autophagic flux blockade and cellular senescence in HT22 cells. These data indicated that H2S protects HT22 cells against HG-induced neuronal senescence by improving autophagic flux via up-regulation of SIRT1, suggesting H2S as a potential treatment strategy for hyperglycemia-induced neuronal senescence and neurotoxicity.

Inhibited Endogenous H2S Generation and Excessive Autophagy in Hippocampus Contribute to Sleep Deprivation-Induced Cognitive Impairment.

Background and Aim: Sleep deprivation (SD) causes deficit of cognition, but the mechanisms remain to be fully established. Hydrogen sulfide (H2S) plays an important role in the formation of cognition, while excessive and prolonged autophagy in hippocampus triggers cognitive disorder. In this work, we proposed that disturbances in hippocampal endogenous H2S generation and autophagy might be involved in SD-induced cognitive impairment. Methods: After treatment of adult male wistar rats with 72-h SD, the Y-maze test, object location test (OLT), novel object recognition test (NORT) and the Morris water maze (MWM) test were performed to determine the cognitive function. The autophagosome formation was observed with electron microscope. Generation of endogenous H2S in the hippocampus of rats was detected using unisense H2S microsensor method. The expressions of cystathionine-ß-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), beclin-1, light chain LC3 II/LC3 I, and p62 in the hippocampus were assessed by western blotting. Results: The Y-maze, OLT, NORT, and MWM test demonstrated that SD-exposed rats exhibited cognitive dysfunction. SD triggered the elevation of hippocampal autophagy as evidenced by enhancement of autophagosome, up-regulations of beclin-1 and LC3 II/LC3 I, and down-regulation of p62. Meanwhile, the generation of endogenous H2S and the expressions of CBS and 3-MST (H2S producing enzyme) in the hippocampus of SD-treated rats were reduced. Conclusion: These results suggested that inhibition of endogenous H2S generation and excessiveness of autophagy in hippocampus are involved in SD-induced cognitive impairment.

Expression and functional characterization of two pathogenesis-related protein 10 genes from Zea mays.

A novel PR10 gene (ZmPR10.1) was isolated from maize and its expression and function were compared with the previous ZmPR10. ZmPR10.1 shares 89.8% and 85.7% identity to ZmPR10 at the nucleotide and amino acid sequence level, respectively. ZmPR10 and ZmPR10.1 were mainly expressed in root tissue with low expression in other tissues. ZmPR10.1 had significantly lower expression than ZmPR10 in all tissues examined. The expression of both ZmPR10 and ZmPR10.1 was induced by most abiotic stresses including SA, CuCl(2), H(2)O(2), coldness, darkness and wounding during the 16-h treatments, and biotic stresses such as Erwinia stewartii and Aspergillus flavus infection. However, ZmPR10.1 was induced only 2 HAT and down-regulated thereafter, whereas ZmPR10 remained induced during the 16-h NAA treatment. Also, inoculation with Erwinia chrysanthemi caused about 2-fold induction in ZmPR10.1 expression 60 HAT but not significant changes for ZmPR10. Both ZmPR10.1 and ZmPR10 showed RNase activity in vitro with an optimal pH and temperature of 6.5 and 55 degrees C. Their RNase activities were significantly inhibited by low concentrations (1.0mM) of Cu(2+), Ag(+), Co(2+), SDS, EDTA or DTT. However, ZmPR10.1 possessed significantly higher (8-fold) specific RNase activity than ZmPR10. Also, ZmPR10.1 showed a stronger inhibition against bacterium Pseudomonas syringae pv. tomato DC3000 in vivo and fungus A. flavus in vitro than ZmPR10, indicating that ZmPR10.1 may also play an important role in host plant defense.