Extracellular silicate uptake and deposition induced by oxidative burst in Saccharina japonica sporophytes (Phaeophyceae)
Extracellular silicate uptake and deposition induced by oxidative burst in Saccharina japonica sporophytes (Phaeophyceae)
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DOI：
10.1016/j.algal.2021.102369
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发表时间：
2021-10
影响因子：
5.1
通讯作者：
H. Mizuta;T. Uji;H. Yasui
中科院分区：
文献类型：
--
作者：
H. Mizuta;T. Uji;H. Yasui
通过培养海带孢子体圆片，研究了在添加和不添加过氧化氢（H2 O2）的培养基中生物硅（Si）在海带孢子体中的沉积过程。H_2O_2培养显著促进了硅盘对硅的吸收。硅酸盐-硅吸收完全抑制处理与溴化钾（KBr），碘过氧化物酶（IPO）的竞争性抑制剂，即使在介质中与H2 O2。此外，在含H2 O2的培养基中，含酚红的盘培养导致溴酚蓝的形成，表明胞外IPO的存在。而在H_2O_2介质中，KBr处理则抑制溴酚蓝的生成。这些结果表明，硅酸盐-Si的吸收激活的胞外IPO自由基氧物种（ROS），如H2 O2的存在下。有趣的是，1 mM水杨酸也促进了硅酸盐-Si的吸收，即使在没有H2 O2的培养基中。此外，硅酸盐-Si的分配的可溶性和细胞壁结合的根皮单宁馏分使用罗丹明123（R123），生物Si的示踪剂，估计。示踪剂荧光检测不仅可溶性，而且细胞壁结合的根皮单宁馏分。R123的荧光组织学检测在质外体的表皮和外皮质层的磁盘，重叠的IPO活性的组织化学分布。这些结果表明，各种胁迫诱导的氧化爆发激活了硅酸盐-Si的吸收，并且在孢子体细胞外基质中存在活性氧和根皮单宁的情况下，细胞外IPO催化了Si的沉积。在此基础上，讨论了海带细胞外硅吸收防御反应的可能机制。
The process of biogenic silicon (Si) deposition in sporophytes of kelp (Saccharina japonica) was investigated by culturing sporophyte disks in the medium with and without hydrogen peroxide (H2O2). Culture with H2O2remarkably promoted silicate-Si uptake by the disks. Silicate-Si uptake was completely inhibited by the treatment with potassium bromide (KBr), a competitive inhibitor of iodoperoxidase (IPO), even in the medium with H2O2. In addition, disk culture with phenol red in the medium with H2O2resulted in the formation of bromophenol blue, indicating the presence of extracellular IPO. However, KBr treatment inhibited the formation of bromophenol blue in the medium with H2O2. These results showed that silicate-Si uptake is activated by extracellular IPO in the presence of radical oxygen species (ROS), such as H2O2. Interestingly, 1 mM salicylic acid also promoted silicate-Si uptake, even in the medium without H2O2. Furthermore, the allocation of silicate-Si to the soluble and cell wall-bound phlorotannin fractions using rhodamine 123 (R123), a tracer of biogenic Si, was estimated. Tracer fluorescence was detected in not only the soluble but also the cell wall-bound phlorotannin fraction. R123 fluorescence was histologically detected in the apoplasts of the epidermal and outer cortical layers of the disk, overlapping the histochemical distribution of IPO activity. These results suggested that silicate-Si uptake is activated by an oxidative burst induced by various stresses, and Si deposition is catalyzed by extracellular IPO in the presence of both ROS and phlorotannin in the extracellular matrix of sporophytes. Based on these findings, the hypothetical mechanisms of the extracellular silicate-Si uptake for defense responses in kelp were discussed.