Lead (Pb) is one of the most serious environmental pollutants. The aquatic fern Salvinia minima Baker is capable to hyper-accumulate Pb in their tissues. However, the molecular mechanisms involved in its Pb accumulation and tolerance capacity are not fully understood. In order to investigate the molecular mechanisms that are activated by S. minima in response to Pb, we constructed a suppression subtractive hybridization library (SSH) in response to an exposure to 40 μM of Pb(NO₃)₂ for 12 h. 365 lead-related differentially expressed sequences tags (ESTs) were isolated and sequenced. Among these ESTs, 143 unique cDNA (97 were registered at the GenBank and 46 ESTs were not registered, because they did not meet the GenBank conditions). Those ESTs were identified and classified into 3 groups according to Blast2GO. In terms of metabolic pathways, they were grouped into 29 KEGG pathways. Among the ESTs, we identified some that might be part of the mechanism that this fern may have to deal with this metal, including abiotic-stress-related transcription factors, some that might be involved in tolerance mechanisms such as ROS scavenging, membrane protection, and those of cell homeostasis recovery.

To validate the SSH library, 4 genes were randomly selected from the library and analyzed by qRT-PCR. These 4 genes were transcriptionally up-regulated in response to lead in at least one of the two tested tissues (roots and leaves). The present library is one of the few genomics approaches to study the response to metal stress in an aquatic fern, representing novel molecular information and tools to understand the molecular physiology of its Pb tolerance and hyperaccumulation capacity. Further research is required to elucidate the functions of the lead-induced genes that remain classified as unknown, to perhaps reveal novel molecular mechanisms of Pb tolerance and accumulation capacity in aquatic plants.

铅（Pb）是最严重的环境污染物之一。水生蕨类植物Salvinia minima Baker能够在其组织中过度积累铅。但是，尚未完全了解其Pb积累和耐受能力的分子机制。为了研究S. minima对Pb激活的分子机制，我们构建了抑制性消减杂交文库（SSH），以应对暴露于40μMPb（NO ₃）_{2的情况。}持续12小时。分离并测序了365个与铅相关的差异表达序列标签（EST）。在这些EST中，有143个独特的cDNA（97个EST在GenBank中注册，而46个EST未注册，因为它们不符合GenBank条件）。根据Blast2GO将这些EST识别并分为3组。就代谢途径而言，它们被分为29个KEGG途径。在EST中，我们确定了一些可能是这种蕨类植物处理这种金属的机制的一部分，包括与非生物胁迫相关的转录因子，还有一些可能参与了耐受机制，例如ROS清除，膜保护，以及细胞稳态恢复的那些。

为了验证SSH库，从库中随机选择了4个基因，并通过qRT-PCR分析。响应于两个被测组织（根和叶）中至少之一的铅，这四个基因在转录上上调。本库是研究水生蕨类植物对金属胁迫的响应的少数基因组学方法之一，代表了新颖的分子信息和工具，可了解其对Pb的耐受性和超积累能力的分子生理学。需要进一步的研究来阐明仍被归类为未知的铅诱导基因的功能，以揭示水生植物对Pb的耐受性和积累能力的新分子机制。