Guo Woei-Jiun, Bundithya Weenun, Goldsbrough Peter B
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA.
Department of Horticulture, Chiangmai University, Chiangmai 50200, Thailand.
New Phytol. 2003 Aug;159(2):369-381. doi: 10.1046/j.1469-8137.2003.00813.x.
• Expression and regulation of Arabidopsis metallothionein (MT) genes were investigated to examine the functions of MTs in plants. • To examine the tissue-specific expression of MT genes, GUS reporter gene activity driven by promoters of MT1a, MT2a, MT2b and MT3 was analysed in transgenic plants. • MT1a and MT2b are expressed in the phloem of all organs and are copper (Cu)-inducible; MT2a and MT3, by contrast, are expressed predominantly in mesophyll cells and are also induced by Cu in young leaves and at root tips. Expression of MT genes is highly induced by Cu in trichomes and increases during senescence. Expression of MT4 genes is restricted to seeds. • We propose that plant MTs have distinct functions in heavy metal homeostasis, especially for Cu: MT1a and MT2b are involved in the distribution of Cu via the phloem, while MT2a and MT3 chaperone excess metals in mesophyll cells and root tips. These functional capabilities may allow MTs to play a role in mobilization of metal ions from senescing leaves and the sequestration of excess metal ions in trichomes.
• 为研究拟南芥金属硫蛋白（MT）基因在植物中的功能，对其表达和调控进行了研究。
• 为检测MT基因的组织特异性表达，分析了MT1a、MT2a、MT2b和MT3启动子驱动的GUS报告基因在转基因植物中的活性。
• MT1a和MT2b在所有器官的韧皮部表达，且受铜（Cu）诱导；相比之下，MT2a和MT3主要在叶肉细胞中表达，在幼叶和根尖也受铜诱导。MT基因的表达在毛状体中受铜高度诱导，并在衰老过程中增加。MT4基因的表达仅限于种子。
• 我们认为植物MT在重金属稳态中具有不同功能，尤其是对铜而言：MT1a和MT2b参与通过韧皮部运输铜，而MT2a和MT3在叶肉细胞和根尖中结合过量金属。这些功能特性可能使MT在衰老叶片中金属离子的动员以及毛状体中过量金属离子的螯合中发挥作用。
