College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China.
Zhejiang Provincial Key Laboratory for Genetic Improvement and Quality Control of Medicinal Plants, Hangzhou Normal University, Hangzhou 311121, China.
Tree Physiol. 2023 Jun 7;43(6):1009-1022. doi: 10.1093/treephys/tpad019.
The toxicity and stress caused by heavy metal contamination has become an important constraint to the growth and flourishing of trees. In particular, species belonging to the genus Taxus, which are the only natural source for the anti-tumor medicine paclitaxel, are known to be highly sensitive to environmental changes. To investigate the response of Taxus spp. to heavy metal stress, we analyzed the transcriptomic profiles of Taxus media trees exposed to cadmium (Cd2+). In total, six putative genes from the metal tolerance protein (MTP) family were identified in T. media, including two Cd2+ stress inducible TMP genes (TmMTP1, TmMTP11 and Taxus media). Secondary structure analyses predicted that TmMTP1 and TmMTP11, which are members of the Zn-CDF and Mn-CDF subfamily proteins, respectively, contained six and four classic transmembrane domains, respectively. The introduction of TmMTP1/11 into the ∆ycf1 yeast cadmium-sensitive mutant strain showed that TmMTP1/11 might regulate the accumulation of Cd2+ to yeast cells. To screen the upstream regulators, partial promoter sequences of the TmMTP1/11 genes were isolated using the chromosome walking method. Several myeloblastosis (MYB) recognition elements were identified in the promoters of these genes. Furthermore, two Cd2+-induced R2R3-MYB TFs, TmMYB16 and TmMYB123, were identified. Both in vitro and in vivo assays confirmed that TmMTB16/123 play a role in Cd2+ tolerance by activating and repressing the expression of TmMTP1/11 genes. The present study elucidated new regulatory mechanisms underlying the response to Cd stress and can contribute to the breeding of Taxus species with high environmental adaptability.
重金属污染所导致的毒性和压力，已经成为树木生长和繁茂的重要制约因素。特别是红豆杉属（Taxus）物种，它们是紫杉醇这种抗癌药物的唯一天然来源，已知对环境变化非常敏感。为了研究红豆杉属植物对重金属胁迫的响应，我们分析了暴露于镉（Cd2+）的欧洲红豆杉（Taxus media）的转录组谱。在欧洲红豆杉中，总共鉴定出了 6 个金属耐受蛋白（MTP）家族的假定基因，包括 2 个 Cd2+应激诱导的 TMP 基因（TmMTP1、TmMTP11 和 Taxus media）。二级结构分析预测，TmMTP1 和 TmMTP11 分别是 Zn-CDF 和 Mn-CDF 亚家族蛋白的成员，分别含有 6 个和 4 个经典的跨膜结构域。将 TmMTP1/11 导入∆ycf1 酵母镉敏感突变株表明，TmMTP1/11 可能调节 Cd2+向酵母细胞的积累。为了筛选上游调控因子，采用染色体步移法分离了 TmMTP1/11 基因的部分启动子序列。在这些基因的启动子中鉴定到了几个髓样细胞瘤（MYB）识别元件。此外，还鉴定到了 2 个 Cd2+诱导的 R2R3-MYB TFs，TmMYB16 和 TmMYB123。体外和体内试验均证实，TmMTB16/123 通过激活和抑制 TmMTP1/11 基因的表达，在 Cd2+耐受中发挥作用。本研究阐明了响应 Cd 胁迫的新调控机制，可为具有高环境适应性的红豆杉属物种的培育做出贡献。
