Influence of rare earth elements on metabolism and related enzyme activity and isozyme expression in Tetrastigma hemsleyanum cell suspension cultures.

The effects of rare earth elements (REEs) not only on cell growth and flavonoid accumulation of Tetrastigma hemsleyanum suspension cells but also on the isoenzyme patterns and activities of related enzymes were studied in this paper. There were no significant differences in enhancement of flavonoid accumulation in T. hemsleyanum suspension cells among La(3+), Ce(3+), and Nd(3+). Whereas their inductive effects on cell proliferation varied greatly. The most significant effects were achieved with 100 µM Ce(3+)and Nd(3+). Under treatment over a 25-day culture period, the maximal biomass levels reached 1.92- and 1.74-fold and the total flavonoid contents are 1.45- and 1.49-fold, than that of control, respectively. Catalase, phenylalanine ammonia-lyase (PAL), and peroxidase (POD) activity was activated significantly when the REE concentration range from 0 to 300 µM, whereas no significant changes were found in superoxide dismutase activity. Differences of esterase isozymes under REE treatment only laid in expression level, and there were no specific bands. The expression level of some POD isozymes strengthened with increasing concentration of REEs within the range of 50-200 µM. When REE concentration was higher than 300 µM, the expression of some POD isozymes was inhibited; meanwhile, some other new POD isozymes were induced. Our results also showed REEs did not directly influence PAL activity. So, we speculated that 50-200 µM REEs could activate some of antioxidant enzymes, adjust some isozymes expression, trigger the defense responses of T. hemsleyanum suspension cells, and stimulate flavonoid accumulation by inducing PAL activity.

Protease inhibitors decrease the resistance of Vitaceae to Plasmopara viticola.

Plasmopara viticola must successfully infect susceptible grapevine cultivars to complete its biological cycle. In resistant grapevine varieties, P. viticola is blocked by the activation of defense mechanisms; these defense mechanisms produce hypersensitive reactions, which are related to programmed cell death. In animals, programmed cell death is dependent on caspase activities. In plants, different caspase-like proteases assume the same functions. To examine the roles of caspase-like proteases in P. viticola-grapevine interactions, three varieties of grapevine with different levels of P. viticola resistance were chosen. These grapevine varieties were treated with either PMSF, a serine protease inhibitor, or E-64, a cysteine protease inhibitor. The development of the pathogen was followed microscopically, and the plant defense reactions were estimated through stilbene quantification. Both protease inhibitor treatments increased the infection rate in the resistant and immune varieties, diminished the production of toxic stilbenes and changed the level of the plants' susceptibility to the pathogen. In particular, after either protease treatment, the cultivar that was originally immune became resistant (hyphae and haustoria were observed), the resistant cultivar reached the level of a susceptible cultivar (sporulation was observed) and the susceptible cultivar became more sensitive (P. viticola colonized the entirety of the leaf mesophyll).

[Callus cultivation and determination of flavonoids from Tetrastigma hemsleyanum].

OBJECTIVE: The feasibility of producting flavonoids from callus of Tetrastigma hemsleyanum was investigated through callus induction, proliferation, differentiation and determination of flavonoids. METHODS: The leaves of sterile plantlet, leaves and stems of wild plants were used as explants to induce calluses; The root tuber, the leaves and calluses were selected for the determination of flavonoids. With ethanol as the solvent, the total flavonoids were extracted by ultrasonic and determined by spectrophotometry at 500 nm after stained with NaNO2-Al(NO3) 3. RESULTS: The optimum medium where the calluses were induced was 2/3MS +2.0 mg/L 6-BA +2.0 mg/L NAA; MS +2.0 mg/L 6-BA +2.0 mg/L NAA was the optimum for callus proliferation; for callus root differentiation, the optimum medium was 1/2MS +1.0 mg/L 6-BA +1.0 mg/L NAA. The content of total flavonoids was 31.121 mg/g in root tuber, 12.830 mg/g in leaves while it was up to 18.088 mg/g in calluses. CONCLUSION: The calluses had a high level of total flavonoids, it could produce flavonoids through the calluses induced by Tetrastigma hemsleyanum in a large scale. In that case, the pressing requirement in medical market will be solved.

[Effects of nitrogen supply on Parthenocissus tricuspidata seedling morphology and nitrogen allocation].

With hydroponic culture, this paper studied the effects of different nitrogen (N) supply levels (0, 0.15, 0.3, 0.45, 0.6, 0.75 g N x L(-1)) on the seedling morphology and N allocation of Parthenocissus tricuspidata. The results showed that lower N supply retarded the development of P. tricuspidata seedling's branch; while higher N supply had significant effects in promoting the seedling's early branching and lowering the branching position on the main stem. Supplying higher amount of N increased the plant biomass and the N concentration in root, leaf and stem significantly. Compared with stem and root, leaf had the highest biomass, accounting for 50% of the total biomass, and the highest N accumulation, accounting for 60%-70% of the total accumulated N.