College of Life Sciences, Laboratory Center of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, China.
BMC Plant Biol. 2020 Feb 4;20(1):58. doi: 10.1186/s12870-020-2272-2.
Hydrogen gas (H) is hypothesised to play a role in plants that are coping with stresses by regulating signal transduction and gene expression. Although the beneficial role of H in plant tolerance to cadmium (Cd) has been investigated previously, the corresponding mechanism has not been elucidated. In this report, the transcriptomes of alfalfa seedling roots under Cd and/or hydrogen-rich water (HRW) treatment were first analysed. Then, the sulfur metabolism pathways were focused on and further investigated by pharmacological and genetic approaches.
A total of 1968 differentially expressed genes (DEGs) in alfalfa seedling roots under Cd and/or HRW treatment were identified by RNA-Seq. The DEGs were classified into many clusters, including glutathione (GSH) metabolism, oxidative stress, and ATP-binding cassette (ABC) transporters. The results validated by RT-qPCR showed that the levels of relevant genes involved in sulfur metabolism were enhanced by HRW under Cd treatment, especially the genes involved in (homo)glutathione metabolism. Additional experiments carried out with a glutathione synthesis inhibitor and Arabidopsis thaliana cad2-1 mutant plants suggested the prominent role of glutathione in HRW-induced Cd tolerance. These results were in accordance with the effects of HRW on the contents of (homo)glutathione and (homo)phytochelatins and in alleviating oxidative stress under Cd stress. In addition, the HRW-induced alleviation of Cd toxicity might also be caused by a decrease in available Cd in seedling roots, achieved through ABC transporter-mediated secretion.
Taken together, the results of our study indicate that H regulated the expression of genes relevant to sulfur and glutathione metabolism and enhanced glutathione metabolism which resulted in Cd tolerance by activating antioxidation and Cd chelation. These results may help to elucidate the mechanism governing H-induced Cd tolerance in alfalfa.
氢气（H）被认为在植物应对压力时通过调节信号转导和基因表达发挥作用。尽管先前已经研究了 H 在植物耐受镉（Cd）中的有益作用，但相应的机制尚未阐明。在本报告中，首先分析了富氢水（HRW）和/或 Cd 处理下紫花苜蓿幼苗根的转录组。然后，通过药理学和遗传学方法重点研究了硫代谢途径，并进一步进行了研究。
通过 RNA-Seq 鉴定了 HRW 和/或 Cd 处理下紫花苜蓿幼苗根中 1968 个差异表达基因（DEG）。这些 DEG 被分为许多簇，包括谷胱甘肽（GSH）代谢、氧化应激和 ABC 转运体。通过 RT-qPCR 验证的结果表明，HRW 在 Cd 处理下增强了与硫代谢相关的相关基因的水平，尤其是涉及（同）谷胱甘肽代谢的基因。用谷胱甘肽合成抑制剂和拟南芥 cad2-1 突变体植物进行的额外实验表明，谷胱甘肽在 HRW 诱导的 Cd 耐受性中起重要作用。这些结果与 HRW 对（同）谷胱甘肽和（同）植物螯合肽含量的影响以及在 Cd 胁迫下缓解氧化应激的作用一致。此外，HRW 诱导的 Cd 毒性减轻也可能是由于 ABC 转运体介导的分泌导致幼苗根中可利用 Cd 减少所致。
综上所述，我们的研究结果表明，H 调节与硫和谷胱甘肽代谢相关的基因的表达，并通过激活抗氧化和 Cd 螯合作用增强谷胱甘肽代谢，从而增强 Cd 耐受性。这些结果可能有助于阐明 H 诱导的紫花苜蓿 Cd 耐受性的机制。
