Bernard Catherine, Roosens Nancy, Czernic Pierre, Lebrun Michel, Verbruggen Nathalie
Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, Campus Plaine-CP242, Bd. du Triomphe, B-1050 Brussels, Belgium.
FEBS Lett. 2004 Jul 2;569(1-3):140-8. doi: 10.1016/j.febslet.2004.05.036.
Thlaspi caerulescens exhibits a unique capacity for cadmium tolerance and accumulation. We investigated the molecular basis of this exceptional Cd(2+) tolerance by screening for T. caerulescens genes, which alleviate Cd(2+) toxicity upon expression in Saccharomyces cerevisiae. This allowed for the isolation of a cDNA encoding a peptide with homology to the C-terminal part of a heavy metal ATPase. The corresponding TcHMA4 full-length sequence was isolated from T. caerulescens and compared to its homolog from Arabidopsis thaliana (AtHMA4). Expression of TcHMA4 and AtHMA4 cDNAs conferred Cd sensitivity in yeast, while expression of TcHMA4-C and AtHMA4-C cDNAs encoding the C-termini of, respectively, TcHMA4 and AtHMA4 conferred Cd tolerance. Moreover, heterologous expression in yeast suggested a higher Cd binding capacity of TcHMA4-C compared to AtHMA4-C. In planta, both HMA4 genes were expressed at a higher level in roots than in shoots. However, TcHMA4 shows a much higher constitutive expression than AtHMA4. Our data indicate that HMA4 could be involved in Cd(2+) transport and possibly in the Cd hyperaccumulation character.
天蓝遏蓝菜表现出对镉的耐受和积累的独特能力。我们通过筛选天蓝遏蓝菜基因来研究这种非凡的Cd(2+)耐受性的分子基础，这些基因在酿酒酵母中表达时可减轻Cd(2+)毒性。这使得我们能够分离出一个编码与重金属ATP酶C末端部分具有同源性的肽的cDNA。从天蓝遏蓝菜中分离出相应的TcHMA4全长序列，并将其与其拟南芥同源物（AtHMA4）进行比较。TcHMA4和AtHMA4 cDNA的表达使酵母对镉敏感，而分别编码TcHMA4和AtHMA4 C末端的TcHMA4-C和AtHMA4-C cDNA的表达则赋予酵母对镉的耐受性。此外，在酵母中的异源表达表明，与AtHMA4-C相比，TcHMA4-C具有更高的镉结合能力。在植物中，两个HMA4基因在根中的表达水平均高于地上部分。然而，TcHMA4的组成型表达比AtHMA4高得多。我们的数据表明，HMA4可能参与Cd(2+)的转运，并且可能与镉超积累特性有关。
