ABSTRACT
Alternative oxidase (AOX) is the terminal oxidase of the mitochondrial respiratory electron transport chain in plant cells and is critical for the balance of mitochondrial hemostasis. In this study, the effect of inhibition of AOX with different concentrations of salicylhydroxamic acid (SHAM) on the tobacco root development was investigated. We show here that AOX inhibition significantly impaired the development of the main root and root hair formation of tobacco. The length of the main root of SHAM-treated tobacco was significantly shorter than that of the control, and no root hairs were formed after treatment with a concentration of 1 mM SHAM or more. The transcriptome analysis showed that AOX inhibition by 1 mM SHAM involved in the regulation of gene expression related to root architecture. A total of 5,855 differentially expressed genes (DEGs) were obtained by comparing SHAM-treated roots with control. Of these, the gene expression related to auxin biosynthesis and perception were significantly downregulated by 1 mM SHAM. Similarly, genes related to cell wall loosening, cell cycle, and root meristem growth factor 1 (RGF1) also showed downregulation on SHAM treatment. Moreover, combined with the results of physiological measurements, the transcriptome analysis demonstrated that AOX inhibition resulted in excessive accumulation of reactive oxygen species in roots, which further induced oxidative damage and cell apoptosis. It is worth noting that when indoleacetic acid (20 nM) and dimethylthiourea (10 mM) were added to the medium containing SHAM, the defects of tobacco root development were alleviated, but to a limited extent. Together, these findings indicated that AOX-mediated respiratory pathway plays a crucial role in the tobacco root development, including root hair formation.
ABSTRACT
OBJECTIVE: To compare the toxicity of Euphorbia pekinensis before and after being processed by vinegar on normal liver cells LO2, and discuss its possible mechanism. METHOD: LO2 cells were cultured in vitro, and processed with different concentrations of crude and vinegar-processed E. pekinensis. MTT assay was used to measure the inhibitory effect of LO2 cell; Hoechst 33258 staining was used to observe the morphological changes in apoptosis cell; Annexin V-FITC flow cytometry was used to analyze the apoptotic rate of LO2 cell; PI staining flow cytometry was used to analyze its impact on cell cycle. The level or content of ALT, AST, LDH, SOD, MDA and GSH were observed as well. RESULT: Compared with the negative control group, crude E. pekinensis at all concentrations could obviously inhibit LO2 cell proliferation, induce LO2 cell apoptosis and cause cell arrest in S phase, with significant differences (P <0.05). E. pekinensis could significantly increase the levels of ALT, AST and LDH (P <0.05) in the supernatant of cell culture fluid, significantly decrease the level of SOD and the content of GSH (P <0.05) , and significantly increase the content of MDA (P <0.05). Compared with the crude E. pekinensis group, E. pekinensis after being vinegar-processed can significantly reduce cell apoptotic rate, cell cycle arrest, activities of ALT, AST, LDH in the supernatant of cell culture fluid (P <0.05) , and remarkably increase the level of SOD and the content of GSH, but reduce the content of MDA in the supernatant of cell culture fluid. CONCLUSION: Vinegar-processed E. pekinensis can release the cytotoxicity of LO2 cell. Its mechanism may be related to the decrease in the oxidative damage of LO2 cells, thereby reducing the cell cycle arrest and apoptosis.
