Objective To search the feasibility of mutation,RdxA gene was analyzed by the metronidazole induction experiment.Method The non-multiple,sensitive H.pylori strains,were selected and subjected to metronidazole induction experiment,which made H.pylori strains transform susceptibility to resistance.Extracted DNA of metronidazole sensitive and resistant pairs of H.pylori strains before and after induced,amplified by PCR and sequenced rdxA gene.Result 4 of 12 H.pylori strains were induced successfully with metronidazole whose MICs increased by 16~64 times.Strains were transferred three times on metronidazole-free medium and the MICs redetermined were the same as those after induced.There was 0.2～0.8% difference between pairs of metronidazole sensitive and resistant H.pylori strains.There was 2.2～2.7% difference between unrelated H.pylori strains.Conclusion The metronidazole induction experiment could make H.pylori acquire stable resistance to metronidazole in a short period and exclude that the natural polymorphism of rdxA gene influenced on mutation analysis.There was good hope that the experiment would become a good method to research metronidazole resistance mechanism

Grape (Vitis vinifera L.) in production is frequently exposed to inadequate light, which significantly affects its agronomic traits via inhibiting their physiological, metabolic and developmental processes. To explore the mechanism how the grape plants respond to the weak light stress, we used 'Yinhong' grape and examined their physiology-biochemistry characteristics and transcriptional profile under different levels of weak light stress. The results showed that grape seedlings upon low intensity shading treatments were not significantly affected. As the shading stress intensity was strengthened, the epidermis cells, palisade tissue, and spongy tissue in the leaves were thinner, the intercellular space between the palisade tissue and spongy tissue was larger compared with that of the control, and the activities of superoxide dismutase, catalase and peroxidase were decreased gradually. Additionally, the soluble protein content increased and the free proline content decreased gradually. Compared with the control, significant changes in plant photosynthetic characteristics and physiology-biochemistry characteristics were observed under high intensity of shading (80%). RNA-seq data showed that the differentially expressed genes between CK and T2, CK and T4, T2 and T4 were 13 913, 13 293 and 14 943, respectively. Most of the enrichment pathways were closely related with the plant's response to stress. Several signaling pathways in response to stress-resistance, e.g. JA/MYC2 pathway and MAPK signal pathway, were activated under weak light stress. The expression level of a variety of genes related to antioxidation (such as polyphenol oxidase and thioredoxin), photosynthesis (such as phytochrome) was altered under weak light stress, indicating that 'Yinhong' grape may activate the antioxidation related pathways to cope with reactive oxygen species (ROS). In addition, it may activate the expression of photosynthetic pigment and light reaction structural protein to maintain the photosynthesis activity. This research may help better understand the relevant physiological response mechanism and facilitate cultivation of grape seedlings under weak light.
Vitis/metabolism* ; Gene Expression Regulation, Plant ; Photosynthesis/genetics* ; Plant Leaves ; Light ; Seedlings/metabolism*