前期克隆了一个编码拟南芥1,4-β-甘露聚糖内水解酶的基因MAN3，发现其通过甘露糖（mannose）介导的信号来调控谷胱甘肽（GSH）依赖的植物螯合肽（PC）合成途径上相关基因表达，从而增加植株对镉（Cd）的积累和耐受。然而， MAN3上游和下游的信号转导组分尚不清楚。最近我们发现一个mannose特异结合蛋白MBL1功能缺失突变体对Cd胁迫敏感，据此推测MAN3可能通过mannose与MBL1互作来启动GSH依赖的PC合成途径上相关基因表达，从而实现植物细胞对Cd信号的应答反应；此外，还筛选了一个可能直接调控MAN3基因转录的MYB转录因子（暂命名为TFx），该基因敲除的突变体tfx对Cd胁迫敏感。本项目拟研究植物响应Cd胁迫过程中MAN3的上游TFx和下游MBL1，阐明一条植物响应Cd胁迫的信号转导通路TFx-MAN3-mannose-MBL1，揭示其调控植物对Cd胁迫响应的机制。

Previously, we cloned Arabidopsis MAN3 gene involved in the regulation of cadmium accumulation and tolerance, which encodes an 1,4-β-mannanase. We found that MAN3 regulates the glutathione (GSH)-dependent phytochelatin (PC) synthesis pathway by coordinated activation of expression of genes involved in PC biosynthesis, which is triggered by mannose-mediated signaling, and thereby enhances Cd accumulation and tolerance in Arabidopsis. However, little is known about signaling components function in upstream and downstream of MAN3 in response to Cd stress. Recently, we found that loss function of MBL1 led to Cd sensitivity, and thereby speculated that MAN3 might trigger expression of genes involved in PC biosynthesis by interaction between mannose and MBL1 to regulate the response of plant cells to Cd stress. In addition, we have also screened a MYB transcription factor (designated as TFx) that possibly directly regulates in transcription of MAN3 gene, and found that the tfx mutants showed enhanced Cd sensitivity. In this project, we proposed to identify and analyze upstream TFx and downstream MBL1 of MAN3 in response of plants to Cd stress, and thereby uncover a TFx-MAN3-mannose-MBL1 signaling pathway and its action mechanism involved in the regulation of the response of plants to Cd stress.