This study investigated the effects of exogenous hydrogen sulfide on the ascorbate and glutathione metabolism in wheat seedlings leaves under water stress. The results showed that pretreatment with sodium hydrosulfide (NaHS), hydrogen sulfide donor, increased the activities of ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase and gamma-glutamylcysteine synthetase, and the contents of reduced ascorbic acid, reduced glutathione, total ascorbate and total glutathione under water stress, compared to control and water stress without NaHS. Meanwhile, pretreatment with NaHS decreased the malondialdehyde content and electrolyte leakage induced by water stress in plants, compared to control and water stress without NaHS. Our results suggested that exogenous hydrogen sulfide alleviated oxidative damage by regulating the ascorbate and glutathione metabolism in wheat seedlings under water stress.

BackgroundRadix Trichosanthis (RT), the dry root tuber of Trichosanthis kirilowii Maxim (Cucurbitaceae), is a traditional Chinese medicine. Although a wide range of saponin pharmacological properties has been identified, to our knowledge, this may be the first report to investigate the crude saponins from RT. The purpose of this study was to delineate the antioxidant activity both in vitro and in vivo by using ethyl acetate (EtOAc), n-butanol, and the mixture of n-butanol and EtOAc fractions.MethodsIn vitro antioxidant activity was detected by using DPPH free radical, hydrogen peroxide scavenging, and reducing power assays. After pretreatment with different fractions saponins at 2 mg/kg/d and 3 mg/kg/d of crude drug, respectively, an established CCl4 induced acute cytotoxicity model was used to evaluate the in vivo antioxidant potential by detection of superoxide dismutase (SOD), malonaldehyde (MDA), lactate dehydrogenase (LDH), and total antioxidant capacity (T-AOC) levels.ResultsThe in vitro assay showed that the antioxidant activity of all the three fractions was promising. The reducing power of the EtOAc and the mixture of n-butanol and EtOAc extracts increased in a dose dependent manner. However, both the n-butanol and the mixture of n-butanol and EtOAc fractions in low dose exhibited in a time dependent manner with prolonged reaction time. As for hydrogen peroxide scavenging capability, the n-butanol fraction mainly demonstrated a time dependent manner, whereas EtOAc fraction showed a dose dependent manner. However, in case of in vivo assay, an increase of SOD and T-AOC and decrease of MDA and LDH levels were only observed in n-butanol (2 mg/kg/d of crude drug) extracts pretreatment group.ConclusionsRT saponins in n-butanol fraction might be a potential antioxidant candidate, as CCl4-induced oxidative stress has been found to be alleviated, which may be associated with the time dependent manner of n-butanol saponins in a low dose. Further studies will be needed to investigate the active individual components in n-butanol extract, in vivo antioxidant activities and antioxidant mechanisms.

IspH is a key enzyme in the last step of the methyl-D-erythritol-4-phosphate (MEP) pathway. Loss of function of IspH can often result in complete yellow or albino phenotype in many plants. Here, we report the characterization of a recessive mutant of maize, zebra7 (zb7), showing transverse green/yellow striped leaves in young plants. The yellow bands of the mutant have decreased levels of chlorophylls and carotenoids with delayed chloroplast development. Low temperature suppressed mutant phenotype, while alternate light/dark cycle or high temperature enlarged the yellow section. Map-based cloning demonstrated that zb7 encodes the IspH protein with a mis-sense mutation in a conserved region. Transgenic silencing of Zb7 in maize resulted in complete albino plantlets that are aborted in a few weeks, confirming that Zb7 is important in the early stages of maize chloroplast development. Zb7 is constitutively expressed and its expression subject to a 16-h light/8-h dark cycle regulation. Our results suggest that the less effective or unstable IspH in zb7 mutant, together with its diurnal expression, are mechanistically accounted for the zebra phenotype. The increased IspH mRNA in the leaves of zb7 at the late development stage may explain the restoration of mutant phenotype in mature stages.

rhm1 is a major recessive disease resistance locus for Southern corn leaf blight (SCLB). To further narrow down its genetic position, F(2) population and BC(1) F(1) population derived from the cross between resistant (H95(rhm) ) and susceptible parents (H95) of maize (Zea mays) were constructed. Using newly developed markers, rhm1 was initially delimited within an interval of 2.5 Mb, and then finally mapped to a 8.56 kb interval between InDel marker IDP961-503 and simple sequence repeat (SSR) marker A194149-1. Three polymorphic markers IDP961-504, IDP B2-3 and A194149-2 were shown to be co-segregated with the rhm1 locus. Sequence analysis of the 8.56 kb DNA fragment revealed that it contained only one putative gene with a predicted amino acid sequence identical to lysine histidine transporter 1 (LHT1). Comparative sequence analysis indicated that the LHT1 in H95(rhm) harbors a 354 bp insertion in its third exon as compared with that of susceptible alleles in B73, H95 and Mo17. The 354 bp insertion resulted in a truncation of the predicted protein of candidate resistance allele (LHT1-H95(rhm) ). Our results strongly suggest LHT1 as the candidate gene for rhm1 against SCLB. The tightly linked molecular markers developed in this study can be directly used for molecular breeding of resistance to Southern corn leaf blight in maize.

The Ragged leaves1 (Rg1) maize mutant frequently develops lesions on leaves, leaf sheaths, and ear bracts. Lesion formation is independent of biotic stress. High-level accumulation of H(2)O(2) revealed by staining Rg1 leaves, with 3',3'-diaminobenzidine and trypan blue, suggested that lesion formation appeared to be due to cell death. Rg1 was initially mapped to an interval around 70.5 Mb in bin 3.04 on the short arm of chromosome 3. Utilizing 15 newly developed markers, Rg1 was delimitated to an interval around 17 kb using 16,356 individuals of a BC1 segregating population. There was only one gene, rp3, predicted in this region according to the B73 genome. Analysis of transcriptome data revealed that 441 genes significantly up-regulated in Rg1 leaves were functionally over-represented. Among those genes, several were involved in the production of reactive oxygen species (ROS). Our results suggested that lesions of Rg1 maize arose probably due to an aberrant rust resistance allele of Rp3, which elicited the accumulation of ROS independent of biotic stress.

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Six new cytochalasans—namely, aspergicytochalasins A–F (1–6)—together with five known analogs were isolated and characterized from the endophytic fungus Aspergillus sp. from the medicinal plant Lonicera japonica. The structures of the new compounds were established by NMR and MS methods as well as single crystal X-ray diffractions. Compounds 3 and 4 showed weak antibacterial activities to Staphylococcus aureus, with MIC values of 128 and 64 μg/mL, respectively. Compounds 1, 3, 5 and 6 showed inhibitory activities on NO production, with IC50 values less than 40 μM.