Role of jasmonic acid in improving tolerance of rapeseed(Brassica napus L.) to Cd toxicity

The well-known detrimental effects of cadmium （Cd） on plants are chloroplast destruction, photosynthetic pigment inhibition, imbalance of essential plant nutrients, and membrane damage. Jasmonic acid （JA） is an alleviator against different stresses such as salinity and drought. However, the functional attributes of JA in plants such as the interactive effects of JA application and Cd on rapeseed in response to heavy metal stress remain unclear. JA at 50 pmol/L was observed in literature to have senescence effects in plants. In the present study, 25 pmol/L JA is ob- served to be a ＂stress ameliorating molecule＂ by improving the tolerance of rapeseed plants to Cd toxicity. JA reduces the Cd uptake in the leaves, thereby reducing membrane damage and malondialdehyde content and increasing the essential nutrient uptake. Furthermore, JA shields the chloroplast against the damaging effects of Cd, thereby in- creasing gas exchange and photosynthetic pigments. Moreover, JA modulates the antioxidant enzyme activity to strengthen the internal defense system. Our results demonstrate the function of JA in alleviating Cd toxicity and its underlying mechanism. Moreover, JA attenuates the damage of Cd to plants. This study enriches our knowledge regarding the use of and protection provided by JA in Cd stress.

Drought-Stimulated Activity of Plasma Membrane Nicotinamide Adenine Dinucleotide Phosphate Oxidase and Its Catalytic Properties in Rice

The activity of plasma membrane （PM） nicotinamide adenine dinucleotide phosphate （NADPH） oxidase and its catalytic properties in rice was investigated under drought stress conditions. Drought stress led to decreased leaf relative water content （RWC） and, as a result of drought-induced oxidative stress, the activities of antioxidant enzymes increased significantly. More interestingly, the intensity of applied water stress was correlated with increased production of H2O2 and O2^- and elevated activity of PM NADPH oxidase, a key enzyme of reactive oxygen species generation in plants. Histochemical analyses also revealed increased H2O2 and O2^- production in drought-stressed leaves. Application of diphenylene iodonium （DPI）, an inhibitor of PM NADPH oxidase, did not alleviate drought-induced production of H2O2 and O2^-. Catalysis experiments indicated that the rice PM NADPH oxidase was partially fiavin-dependent. The pH and temperature optima for this enzyme were 9.8 and 40 ℃, respectively. In addition, drought stress enhanced the activity under alkaline pH and high temperature conditions. These results suggest that a complex regulatory mechanism, associated with the NADPH oxidase-H2O2 system, is involved in the response of rice to drought stress.

Response of seed tocopherols in oilseed rape to nitrogen fertilizer sources and application rates

Tocopherols （Tocs） are vital scavengers of reactive oxygen species （ROS） and important seed oil quality indicators. Nitrogen （N） is one of the most important fertilizers in promoting biomass and grain yield in crop production. However, the effect of different sources and application rates of N on seed Toc contents in oilseed rape is poorly understood. In this study, pot trials were conducted to evaluate the effect of two sources of N fertilizer （urea and ammonium nitrate）. Each source was applied to five oilseed rape genotypes （Zheshuang 72, Jiu-Er-1358, Zheshuang 758, Shiralee, and Pakola） at three different application rates （0.41 g/pot （N1）, 0.81 g/pot （N2）, and 1.20 g/pot （N3））. Results indicated that urea increased α-, y-, and total Toc （T-Toc） more than did ammonium nitrate. N3 was proven as the most efficient application rate, which yielded high contents of y-Toc and T-Toc. Highly significant correlations were observed between Toc isomers, T-Toc, and α-/y-Toc ratio. These results clearly demonstrate that N sources and application rates significantly affect seed Toc contents in oilseed rape.

Arabidopsis thaliana NOP10 is required for gametophyte formation

The female gametophyte is crucial for sexual reproduction of higher plants, yet little is known about the molecular mechanisms underlying its development. Here, we report that Arabidopsis thaliana NOP10 （AtNOP10） is required for female gametophyte formation. AtNOP10 was expressed predominantly in the seedling and reproductive tissues, including anthers, pollen grains, and ovules. Mutations in AtNOP10 interrupted mitosis of the functional megaspore during early development and prevented polar nuclear fusion in the embryo sacs. AtNOP10 shares a high level of amino acid sequence similarity with Saccharornycescerevisiae （yeast） NOPIo （ScNOP1o）, an important compo- nent of the H/ACA small nucleolar ribonucleoprotein particles （H/ACA snoRNPs） implicated in 18S rRNA synthe- sis and rRNA pseudouridylation. Heterologous expression of ScNOP10 complemented the mutant phenotype of Atnop10. Thus, AtNOPIo influences functional megaspore mitosis and polar nuclear fusion during gametophyte formation in Arabidopsis.