State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; College of Advanced Agricultural Sciences, Zhejiang A & F University, Hangzhou 311300, China.
Sci Total Environ. 2023 Dec 15;904:166644. doi: 10.1016/j.scitotenv.2023.166644. Epub 2023 Sep 1.
Although auxin has been linked to plants' responses to cadmium (Cd) stress, the exact mechanism is yet elusive. The objective of the current investigation was to determine the role and the mechanism of auxin in controlling rice's Cd accumulation. Rice roots with Cd stress have higher endogenous auxin levels, and exogenous auxin combined Cd treatment could reduce root cell wall's hemicellulose content when compared with Cd treatment alone, which in turn reduced its fixation of Cd, as well as decreased the expression of OsCd1 (a major facilitator superfamily gene), OsNRAMP1/5 (Natural Resistance-Associated Macrophage Protein 1/5), OsZIP5/9 (Zinc Transporter 5/9), and OsHMA2 (Heavy Metal ATPase 2) that participated in Cd uptake and root to shoot translocation. Furthermore, less Cd accumulated in the shoots as a result of auxin's impact in increasing the expression of OsCAL1 (Cadmium accumulation in Leaf 1), OsABCG36/OsPDR9 (G-type ATP-binding cassette transporter/Pleiotropic drug resistance 9), and OsHMA3, which were in charge of Cd efflux and sequestering into vacuoles, respectively. Additionally, auxin decreased endogenous nitric oxide (NO) levels and antioxidant enzyme activity, while treatment of a NO scavenger-cPTIO-reduced auxin's alleviatory effects. In conclusion, the rice's ability to tolerate Cd toxicity was likely increased by the auxin-accelerated cell wall Cd exclusion mechanism, a pathway that controlled by the buildup of NO.
尽管生长素已被证明与植物对镉（Cd）胁迫的反应有关，但确切的机制仍不清楚。本研究旨在确定生长素在控制水稻 Cd 积累中的作用和机制。镉胁迫下的水稻根具有更高的内源性生长素水平，与单独 Cd 处理相比，外源生长素与 Cd 联合处理可降低根细胞壁半纤维素的含量，从而减少 Cd 的固定，并降低 OsCd1（主要易化剂超家族基因）、OsNRAMP1/5（天然抗性相关巨噬细胞蛋白 1/5）、OsZIP5/9（锌转运蛋白 5/9）和 OsHMA2（重金属 ATP 酶 2）的表达，这些基因参与 Cd 的摄取和根到茎的转运。此外，由于生长素增加了 OsCAL1（叶 1 中 Cd 的积累）、OsABCG36/OsPDR9（G 型 ATP 结合盒转运蛋白/多药耐药 9）和 OsHMA3 的表达，从而促进了 Cd 的外排和液泡隔离，因此 Cd 在地上部的积累减少。此外，生长素降低了内源性一氧化氮（NO）水平和抗氧化酶活性，而 NO 清除剂 cPTIO 的处理则降低了生长素的缓解作用。总之，生长素通过加速细胞壁 Cd 排除机制提高了水稻对 Cd 毒性的耐受性，该途径受 NO 积累的控制。
