Graduate school of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan.
Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan.
Plant Cell Physiol. 2019 Aug 1;60(8):1683-1701. doi: 10.1093/pcp/pcz082.
Plants are considered to absorb sulfur from their roots in the form of sulfate. In bacteria like Escherichia coli, thiosulfate is a preferred sulfur source. It is converted into cysteine (Cys). This transformation consumes less NADPH and ATP than sulfate assimilation into Cys. In Saccharomyces cerevisiae, thiosulfate promoted growth more than sulfate. In the present study, the availability of thiosulfate, the metabolite transformations and gene expressions it induces were investigated in Arabidopsis and rice as model dicots and monocots, respectively. In Arabidopsis, the thiosulfate-amended plants had lower biomass than those receiving sulfate when sulfur concentrations in the hydroponic medium were above 300 μM. In contrast, rice biomass was similar for plants raised on thiosulfate and sulfate at 300 μM sulfur. Therefore, both plants can use thiosulfate but it is a better sulfur source for rice. In both plants, thiosulfate levels significantly increased in roots following thiosulfate application, indicating that the plants absorbed thiosulfate into their root cells. Thiosulfate is metabolized in plants by a different pathway from that used for sulfate metabolism. Thiosulfate increases plant sulfide and cysteine persulfide levels which means that plants are in a more reduced state with thiosulfate than with sulfate. The microarray analysis of Arabidopsis roots revealed that 13 genes encoding Cys-rich proteins were upregulated more with thiosulfate than with sulfate. These results together with those of the widely targeted metabolomics analysis were used to proposes a thiosulfate assimilation pathway in plants.
植物被认为以硫酸盐的形式从根部吸收硫。在大肠杆菌等细菌中，硫代硫酸盐是首选的硫源。它被转化为半胱氨酸（Cys）。与硫酸盐转化为 Cys 相比，这种转化消耗的 NADPH 和 ATP 更少。在酿酒酵母中，硫代硫酸盐比硫酸盐更能促进生长。在本研究中，分别以拟南芥和水稻为模式双子叶植物和单子叶植物，研究了硫代硫酸盐的可用性、它诱导的代谢产物转化和基因表达。在拟南芥中，当水培介质中的硫浓度高于 300 μM 时，添加硫代硫酸盐的植物的生物量低于接受硫酸盐的植物。相比之下，当硫浓度为 300 μM 时，水稻在硫代硫酸盐和硫酸盐上的生物量相似。因此，两种植物都可以利用硫代硫酸盐，但它是水稻的更好的硫源。在这两种植物中，根中硫代硫酸盐的水平在施用硫代硫酸盐后显著增加，表明植物将硫代硫酸盐吸收到其根细胞中。植物中硫代硫酸盐的代谢途径与硫酸盐代谢途径不同。硫代硫酸盐增加了植物的硫化物和半胱氨酸过硫化物水平，这意味着植物在有硫代硫酸盐的情况下比有硫酸盐的情况下更还原。拟南芥根的微阵列分析显示，13 个编码富含半胱氨酸的蛋白质的基因在用硫代硫酸盐处理时比用硫酸盐处理时的上调更为显著。这些结果与广泛靶向代谢组学分析的结果一起，用于提出植物中硫代硫酸盐同化途径。
