[Heavy metal-transport proteins in plants: a review].

The heavy metals in soil not only damage plant growth, but also threaten the health of human beings and animals through food chain. Heavy metal-transport proteins play crucial roles in the heavy metals uptake and tolerance of plants. Plant heavy metal-transport proteins can be classified as metal-uptake proteins and metal-efflux proteins. The metal-uptake proteins can transport essential heavy metals into cytoplasm, and also, transport toxic heavy metals into cytoplasm due to the absence of essential heavy metals or the competition among ions. The metal-efflux proteins are a group of detoxification proteins, which can efflux excess and toxic heavy metals from cytoplasm, or move these metals into vacuole. In recent years, the associations between elevated steady-state transcript levels of heavy metal-transporter genes and metal accumulation in plants have been revealed, and many heavy metal-transport proteins have been cloned and identified. In this paper, the metal affinity, tissue-specific gene expression, and cellular location of representative heavy metal-transport proteins were reviewed.