Metallothionein deficiency impacts copper accumulation and redistribution in leaves and seeds of Arabidopsis.

Most angiosperm genomes contain several genes encoding metallothionein (MT) proteins that can bind metals including copper (Cu) and zinc (Zn). Metallothionein genes are highly expressed under various conditions but there is limited information about their function. We have studied Arabidopsis mutants that are deficient in multiple MTs to learn about the functions of MTs in plants. T-DNA insertions were identified in four of the five Arabidopsis MT genes expressed in vegetative tissues. These were crossed to produce plants deficient in four MTs (mt1a/mt2a/mt2b/mt3). The concentration of Cu was lower in seeds but higher in old leaves of the quad-MT mutant compared to wild-type plants. Experiments with stable isotopes showed that Cu in seeds came from two sources: directly from roots and via remobilization from other organs. Mobilization of Cu out of senescing leaves was disrupted in MT-deficient plants. Tolerance to Cu, Zn and paraquat was unaffected by MT deficiency but these plants were slightly more sensitive to cadmium (Cd). The quad-MT mutant showed no change in resistance to a number of microbial pathogens, or in the progression of leaf senescence. Although these MTs are not required to complete the plant's life cycle, MTs are important for Cu homeostasis and distribution in Arabidopsis.

Cu2+-selective NIR fluorescence sensor based on heptamethine cyanine in aqueous media and its application.

A near-infrared (NIR) colorimetric fluorescence sensor, Cy7C3, based on heptamethine cyanine dye was synthesized for determining the presence of Cu2+ ions. The sensor showed highly sensitive fluorescence quenching toward Cu2+ ions in acetonitrile/buffer solution at physiological pH with long emission wavelength of 718 nm. Cy7C3 also provided an excellent selectivity to Cu2+ ions over other competing metal ions, with a low detection limit of 9 ppb, which was lower than the maximum concentration of Cu2+ ions in drinking water of U.S. EPA. Cy7C3 could achieve naked-eye detection of Cu2+ ions via the color change from blue to colorless, which allowed determination of Cu2+ ions in hydroponic fertilizers. Additionally, the sensor was developed to detect Cu2+ ions in HepG2 cancer cells via fluorescence imaging.

Development of genotype-independent regeneration system for transformation of rice (Oryza sativa ssp. indica).

Rice (Oryza sativa ssp. indica) is an important economic crop in many countries. Although a variety of conventional methods have been developed to improve this plant, manipulation by genetic engineering is still complicated. We have established a system of multiple shoot regeneration from rice shoot apical meristem. By use of MS medium containing 4 mg L(-1) thidiazuron (TDZ) multiple shoots were successfully developed directly from the meristem without an intervening callus stage. All rice cultivars tested responded well on the medium and regenerated to plantlets that were readily transferred to soil within 5-8 weeks. The tissue culture system was suitable for Agrobacterium-mediated transformation and different factors affecting transformation efficiency were investigated. Agrobacterium strain EHA105 containing the plasmid pCAMBIA1301 was used. The lowest concentration of hygromycin B in combined with either 250 mg L(-1) carbenicillin or 250 mg L(-1) cefotaxime to kill the rice shoot apical meristem was 50 mg L(-1) and carbenicillin was more effective than cefotaxime. Two-hundred micromolar acetosyringone had no effect on the efficiency of transient expression. Sonication of rice shoot apical meristem for 10 s during bacterial immersion increased transient GUS expression in three-day co-cultivated seedlings. The gus gene was found to be integrated into the genome of the T(0) transformant plantlets.