Lindberg Sylvia, Landberg Tommy, Greger Maria
Department of Plant Biology and Forest Genetics, SLU, Box 7080, 750 07, Uppsala, Sweden.
Planta. 2004 Jul;219(3):526-32. doi: 10.1007/s00425-004-1256-z. Epub 2004 Apr 7.
The mechanism for cadmium (Cd2+) uptake into the cytosol of protoplasts from 5- to 7-day-old wheat seedlings (Triticum aestivum L. cv. Kadett) was investigated by a new method, using fluorescence microscopy and the heavy metal-specific fluorescent dye, 5-nitrobenzothiazole coumarin, BTC-5N. Cadmium fluorescence gradually increased in the cytosol of shoot and root protoplasts upon repeated additions of CdCl2 to the external medium, reflecting an uptake of Cd2+. The uptake was inhibited by calcium and potassium chloride, as well as by Verapamil and tetraethylammonium (TEA), inhibitors of calcium and potassium channels, respectively. Calcium competitively inhibited the cadmium uptake. The metabolic inhibitors vanadate and dinitrophenol partly inhibited the uptake, suggesting it was dependent on membrane potential. The results indicate that cadmium is taken up by channels permeable to both calcium and potassium. The total uptake of cadmium into the protoplasts was also detected by unidirectional flux analyses using 109Cd2+, and showed approximately the same maximal concentration of Cd2+ as the fluorescence measurements. By combining the two methods it is possible to detect both uptake into the cytosol and into the vacuole.
采用荧光显微镜和重金属特异性荧光染料5-硝基苯并噻唑香豆素（BTC-5N），通过一种新方法研究了5至7日龄小麦幼苗（普通小麦品种Kadett）原生质体细胞质中镉（Cd2+）的吸收机制。向外部培养基中反复添加CdCl2后，茎和根原生质体细胞质中的镉荧光逐渐增加，这反映了Cd2+的吸收。这种吸收受到氯化钙、氯化钾以及分别作为钙通道和钾通道抑制剂的维拉帕米和四乙铵（TEA）的抑制。钙竞争性抑制镉的吸收。代谢抑制剂钒酸盐和二硝基苯酚部分抑制了这种吸收，表明其依赖于膜电位。结果表明，镉是通过对钙和钾都通透的通道被吸收的。使用109Cd2+通过单向通量分析也检测到了镉向原生质体的总吸收，并且显示出与荧光测量大致相同的Cd2+最大浓度。通过结合这两种方法，可以检测到镉向细胞质和液泡中的吸收。
