Characterization of three novel stem rot pathogens and their antagonistic endophytic bacteria associated with Cistanche deserticola.

Cistanche deserticola is a precious Chinese medicinal material with extremely high health care and medicinal value. In recent years, the frequent occurrence of stem rot has led to reduced or even no harvests of C. deserticola. The unstandardized use of farm chemicals in the prevention and control processes has resulted in excessive chemical residues, threatening the fragile desert ecological environment. Therefore, it is urgent to explore safe and efficient prevention and control technologies. Biocontrol agents, with the advantages of safety and environment-friendliness, would be an important idea. The isolation, screening and identification of pathogens and antagonistic endophytic bacteria are always the primary basis. In this study, three novel pathogens causing C. deserticola stem rot were isolated, identified and pathogenicity tested, namely Fusarium solani CPF1, F. proliferatum CPF2, and F. oxysporum CPF3. For the first time, the endophytic bacteria in C. deserticola were isolated and identified, of which 37 strains were obtained. Through dual culture assay, evaluation experiment and tissue culture verification, a biocontrol candidate strain Bacillus atrophaeus CE6 with outstanding control effect on the stem rot was screened out. In the tissue culture system, CE6 showed excellent control effect against F. solani and F. oxysporum, with the control efficacies reaching 97.2% and 95.8%, respectively, indicating its great potential for application in the production. This study is of great significance for the biocontrol of plant stem rot and improvement of the yield and quality of C. deserticola.

[Molecular mechanism of beta cell apoptosis induced by p58 in high glucose medium].

Type 2 diabetes is a complex disorder with a strong genetic background. CDC2L2 is one of the susceptibility genes of type 2 diabetes in Chinese Han population in northern area. The relationship between CDC2L2 and type 2 diabetes remains unknown. In this paper, the function and its molecular pathway of p58, a protein coded by CDC2L2, in beta cell apoptosis were investigated. INS-1 cells cultured in high glucose (20 mmol/L) medium were divided into control, vector control (transfected with pcDNA3.0) and experimental (transfected with pcDNA3.0-HA-p58) groups. Beta cell apoptosis level was detected by Annexin V-FITC/PI double staining assay. The flow cytometry results showed that in high glucose medium (20 mmol/L), high expression of p58 increased beta cell apoptosis significantly compared with that in blank and vector controls (P<0.01, P<0.05). Western blot revealed that the expressions of Caspase-3, Bax and cytochrome C in cytoplasm increased significantly (P<0.05, P<0.01, P<0.01), whereas the expression of Bcl-2 decreased significantly (P<0.05) in the INS-1 cells with high expression of p58, compared with those in both control groups. However, the Bad and Bik expression levels of INS-1 cells did not show obviously changes compared with those in both controls. The above results suggest that in high glucose condition, p58 may induce INS-1 cell apoptosis through up-regulating the expression of Bax and down-regulating the expression of Bcl-2, since both of them could promote the release of cytochrome C into cytoplasm, and finally activate Caspase-3. These results provide an important basis for the further exploration of the molecular mechanism of beta cell apoptosis induced by CDC2L2.