Schiller Michaela, Hegelund Josefine N, Pedas Pai, Kichey Thomas, Laursen Kristian H, Husted Søren, Schjoerring Jan K
Plant and Soil Science Section, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, 40 Thorvaldsensvej, DK-1871, Frederiksberg C, Copenhagen, Denmark.
Plant Cell Environ. 2014 Feb;37(2):353-67. doi: 10.1111/pce.12158. Epub 2013 Jul 25.
The barley genome encodes a family of 10 metallothioneins (MTs) that have not previously been subject to extensive gene expression profiling. We show here that expression of MT1a, MT2b1, MT2b2 and MT3 in barley leaves increased more than 50-fold during the first 10 d after germination. Concurrently, the root-specific gene MT1b1 was 1000-fold up-regulated. Immunolocalizations provided the first evidence for accumulation of MT1a and MT2a proteins in planta, with correlation to transcript levels. In developing grains, MT2a and MT4 expression increased 4- and 300-fold over a 28-day-period after pollination. However, among the MT grain transcripts MT2c was the most abundant, whereas MT4 was the least abundant. Excess Cu up-regulated three out of the six MTs expressed in leaves of young barley plants. In contrast, most MTs were down-regulated by excess Zn or Cd. Zn starvation led to up-regulation of MT1a, whereas Cu starvation up-regulated MT2a, which has two copper-responsive elements in the promoter. Arabidopsis lines constitutively overexpressing barley MT2a showed increased sensitivity to excess Cd and Zn but no Cu-induced response. We suggest that barley MTs are differentially involved in intracellular homeostasis of essential metal ions and that a subset of barley MTs is specifically involved in Cu detoxification.
大麦基因组编码一个由10种金属硫蛋白（MTs）组成的家族，此前尚未对其进行广泛的基因表达谱分析。我们在此表明，在发芽后的前10天里，大麦叶片中MT1a、MT2b1、MT2b2和MT3的表达增加了50倍以上。同时，根特异性基因MT1b1上调了1000倍。免疫定位为MT1a和MT2a蛋白在植物体内的积累提供了首个证据，且与转录水平相关。在发育中的籽粒中，授粉后28天内MT2a和MT4的表达分别增加了4倍和300倍。然而，在MT籽粒转录本中，MT2c最为丰富，而MT4最不丰富。过量的铜上调了在大麦幼苗叶片中表达的6种MT中的3种。相反，大多数MTs在过量的锌或镉作用下被下调。锌饥饿导致MT1a上调，而铜饥饿上调MT2a，其启动子中有两个铜响应元件。组成型过表达大麦MT2a的拟南芥株系对过量的镉和锌表现出更高的敏感性，但对铜诱导无反应。我们认为，大麦MTs在必需金属离子的细胞内稳态中发挥不同作用，且大麦MTs的一个子集专门参与铜解毒。
