In this study, the effect of brassinosteroid(BR) on the physiological and biochemical conditions of 2-year-old Panax notoginseng under the cadmium stress was investigated by the pot experiments. The results showed that cadmium treatment at 10 mg·kg~(-1) inhibited the root viability of P. notoginseng, significantly increased the content of H_2O_2 and MDA in the leaves and roots of P. noto-ginseng, caused oxidative damage of P. notoginseng, and reduced the activities of SOD and CAT. Cadmium stress reduced the chlorophyll content of P. notoginseng, increased leaf F_o, reduced F_m, F_v/F_m, and PIABS, and damaged the photosynthesis system of P. notoginseng. Cadmium treatment increased the soluble sugar content of P. notoginseng leaves and roots, inhibited the synthesis of soluble proteins, reduced the fresh weight and dry weight, and inhibited the growth of P. notoginseng. External spray application of 0.1 mg·L~(-1) BR reduced the H_2O_2 and MDA content in P. notoginseng leaves and roots under the cadmium stress, alleviated cadmium-induced oxidative damage to P. notoginseng, improved the antioxidant enzyme activity and root activity of P. notoginseng, increased the content of chlorophyll, reduced the F_o of P. notoginseng leaves, increased F_m, F_v/F_m, and PIABS, alleviated the cadmium-induced damage to the photosynthesis system, and improved the synthesis ability of soluble proteins. In summary, BR can enhance the anti-cadmium stress ability of P. notoginseng by regulating the antioxidant enzyme system and photosynthesis system of P. notoginseng under the cadmium stress. In the context of 0.1 mg·L~(-1) BR, P. notoginseng can better absorb and utilize light energy and synthesize more nutrients, which is more suitable for the growth and development of P. notoginseng.
Cadmium/metabolism* ; Antioxidants/pharmacology* ; Panax notoginseng ; Brassinosteroids/pharmacology* ; Chlorophyll/metabolism* ; Plant Roots/metabolism* ; Stress, Physiological

Plant adaptation to adverse environment depends on transmitting the external stress signals into internal signaling pathways, and thus forming a variety of stress response mechanisms during evolution. Brassinosteroids (BRs) is a steroid hormone and widely involved in plant growth, development and stress response. BR is perceived by cell surface receptors, including the receptor brassinosteroid-insensitive 1 (BRI1) and the co-receptor BRI1-associated-kinase 1 (BAK1), which in turn trigger a signaling cascade that leads to the inhibition of BIN2 and activation of BES1/BZR1 transcription factors. BES1/BZR1 can directly regulate the expression of thousands of downstream responsive genes. Studies in the model plant Arabidopsis thaliana have shown that members of BR biosynthesis and signal transduction pathways, particularly protein kinase BIN2 and its downstream transcription factors BES1/BZR1, can be extensively regulated by a variety of environmental factors. In this paper, we summarize recent progresses on how BR biosynthesis and signal transduction are regulated by complex environmental factors, as well as how BR and environmental factors co-regulate crop agronomic traits, cold and salt stress responses.
Arabidopsis/metabolism* ; Brassinosteroids/pharmacology* ; DNA-Binding Proteins/metabolism* ; Gene Expression Regulation, Plant ; Stress, Physiological

Brassinosteroids, a group of plant steroid hormones, regulate many aspects of plant growth and development. We and other have previously solved the crystal structures of BRI1(LRR) in complex with brassinolide, the most active brassinosteroid identified thus far. Although these studies provide a structural basis for the recognition of brassinolide by its receptor BRI1, it still remains poorly understood how the hormone differentiates among its conserved receptors. Here we present the crystal structure of the BRI1 homolog BRL1 in complex with brassinolide. The structure shows that subtle differences around the brassinolide binding site can generate a striking effect on its recognition by the BRI1 family of receptors. Structural comparison of BRL1 and BRI1 in their brassinolide-bound forms reveals the molecular basis for differential binding of brassinolide to its different receptors, which can be used for more efficient design of plant growth regulators for agricultural practice. On the basis of our structural studies and others' data, we also suggest possible mechanisms for the activation of BRI1 family receptors.
Amino Acid Sequence ; Arabidopsis ; metabolism ; Arabidopsis Proteins ; chemistry ; metabolism ; Binding Sites ; Brassinosteroids ; chemistry ; Crystallography, X-Ray ; Molecular Sequence Data ; Protein Kinases ; chemistry ; metabolism ; Protein Structure, Tertiary ; Recombinant Proteins ; genetics ; Sequence Alignment ; Steroids, Heterocyclic ; chemistry

AIMTo investigate the effect of brassinolide, a plant growth modulator, on multidrug resistance (MDR) of human T lymphoblastoid cell line CCRF-VCR 1000 which was obtained by progressively addition of vincristine (VCR) to sensitive CCRF-CEM cells, and to explore preliminarily the mechanism of reversing action.

METHODSMTT method was used to detect the resistant factor of resistant cell line and the reversing fold after addition of brassinolide. The intracellular accumulation of rhodamine 123, a fluorescent dye transported by P-glycoprotein was detected by flow cytometry, the catalytic activity of topoisomerase II was assessed by Sulliven method to find the effect of brassinolide on resistance. The protein expression of p53 was measured using Western blotting in the sensitive cells and resistant cells to explore the effect of brassinolide.

RESULTSThe resistant factors of CCRF-VCR cells on adriamycin, VP-16 and VCR are respectively as 153.1, 55.9 and 8123.1 folds comparing to the sensitive cell line CCRF-CEM. After treatment of brassinolide under the concentration of 0.001 - 10.0 microg x mL(-1), the resistance of CCRF-VCR was reversed partly with the reversing folds respectively as 4.4 - 11.6. The intracellular accumulation of rhodamine 123 was significantly reduced in the resistant cells. After treatment of brassinolide, the accumulation increased, the level of fluorescent dye was situated between resistant cells and sensitive cells. No alteration of the catalytic activity of topoisomerase II was found among three groups. The level of protein expression of p53 in resistant cells was higher than that of sensitive cells. After brassinolide treatment, the expression of p53 in CCRF-VCR cells restored to the level of sensitive cells.

CONCLUSIONBrassinolide could effectively reverse the resistance of CCRF-VCR cells by inhibiting the effusion of drug transported by P-glucoprotein. To down regulate the abnormal expression of p53 maybe one of the mechanisms of reversing MDR for brassinolide.

Brassica rapa ; chemistry ; Brassinosteroids ; Cell Line, Tumor ; drug effects ; Cholestanols ; isolation & purification ; pharmacology ; Drug Resistance, Multiple ; drug effects ; Drug Resistance, Neoplasm ; drug effects ; Humans ; Leukemia, T-Cell ; metabolism ; pathology ; Plant Growth Regulators ; pharmacology ; Pollen ; chemistry ; Steroids, Heterocyclic ; isolation & purification ; pharmacology ; Tumor Suppressor Protein p53 ; metabolism