Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, 710-0046 Japan.
Plant Cell Physiol. 2020 Mar 1;61(3):481-491. doi: 10.1093/pcp/pcz213.
One of the most important roles of plant roots is to take up mineral elements for their growth. Although several genes involved in root growth have been identified, the association between root structure and mineral element uptake is less investigated. In this study, we isolated a rice mutant (dice1, defective in cell elongation 1) with short-root phenotype. This mutant was characterized by partial defect in the formation of root outer cell layers. Mapping of the responsible gene revealed that the short-root phenotype in the mutant was caused by a single-nucleotide substitution of a gene encoding a membrane-anchored endo-1,4-beta-glucanase (OsGlu3). The growth of both the roots and shoots was partially recovered with increasing strength of nutrient solution and glucose in the mutant. The mutant showed a decreased uptake (normalized by root dry weight) for Mg, Mn, Fe, Cu, Zn, Cd, As and Ge but increased uptake for K and Ca. The expression level of some transporter genes including OsLsi1 and OsLsi2 for Si uptake and OsNramp5 for Mn uptake was significantly decreased in the mutant compared with the wild-type (WT) rice. Furthermore, the cellular localization of OsLsi1 was altered; OsLsi1 localized at the root exodermis of the WT rice was changed to be localized to other cell layers of the mutant roots. However, this localization became normal in the presence of exogenous glucose in the mutant. Our results indicate that a normal root structure is required for maintaining the expression and localization of transporters involved in the mineral element uptake.
植物根系的一个重要作用是吸收矿物质元素以促进其生长。尽管已经鉴定出了几个参与根系生长的基因，但根系结构与矿物质元素吸收之间的联系还没有得到深入研究。在本研究中，我们分离得到了一个水稻突变体（dice1，细胞伸长缺陷 1），表现为短根表型。该突变体的特征是根外层细胞层的形成部分缺陷。基因定位表明，该突变体的短根表型是由编码膜锚定内-1,4-β-葡聚糖酶（OsGlu3）的基因的单个核苷酸取代引起的。随着营养液和葡萄糖浓度的增加，突变体的根和茎的生长得到了部分恢复。与野生型（WT）水稻相比，突变体对 Mg、Mn、Fe、Cu、Zn、Cd、As 和 Ge 的吸收（按根干重标准化）减少，而对 K 和 Ca 的吸收增加。与 WT 水稻相比，一些转运体基因的表达水平，包括 Si 吸收的 OsLsi1 和 OsLsi2 以及 Mn 吸收的 OsNramp5，在突变体中显著降低。此外，OsLsi1 的细胞定位发生改变；WT 水稻中 OsLsi1 定位于根外表皮的位置在突变体根中改变为定位于其他细胞层。然而，在突变体中添加外源葡萄糖后，这种定位变得正常。我们的结果表明，正常的根结构对于维持参与矿物质元素吸收的转运体的表达和定位是必需的。
