MOE Key Laboratory of Environment Remediation and Ecological Health, College of Natural Resource & Environmental Sciences, Zhejiang University, Hangzhou, 310058, China.
Zhejiang Provincial Cultivated Land Quality and Fertilizer Administration Station, Hangzhou, 310020, China.
Environ Pollut. 2024 Dec 15;363(Pt 2):125241. doi: 10.1016/j.envpol.2024.125241. Epub 2024 Nov 4.
Microbial secondary metabolites are crucial in plant-microorganism interactions, regulating plant growth and stress responses. In this study, we found that cyclo(-Phe-Pro), a proline-based cyclic dipeptide secreted by many microorganisms, alleviated aluminum toxicity in wheat roots by increasing root growth, decreasing callose deposition, and decreasing Al accumulation. Cyclo(-Phe-Pro) also significantly reduced Al-induced reactive oxygen species (ROS) with HO, O, and •OH levels decreasing by 19.1%, 42.8%, and 17.9% in root tips, thus protecting the plasma membrane from oxidative damage. Although Al stress increased the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) in wheat roots, cyclo(-Phe-Pro) application reduced these enzyme activities. However, compared to the Al treatment, cyclo(-Phe-Pro) application increased DPPH and FRAP activities by 16.8% and 14.9%, indicating increased non-enzymatic antioxidant capacity in wheat roots. We observed that Al caused the oxidation of ascorbate (AsA) and glutathione (GSH) to dehydroascorbate (DHA) and glutathione disulfide (GSSG), respectively. Under Al stress, cyclo(-Phe-Pro) treatment maintained reduced AsA and GSH levels, as well as high AsA/DHA and GSH/GSSG redox pair ratios in wheat roots. High AsA/DHA and GSH/GSSG ratios can reduce Al toxicity by neutralizing free radicals and restoring redox homeostasis via antioxidant properties. These results suggest that cyclo(-Phe-Pro) maintains ASA- and GSH-dependent redox homeostasis to alleviate oxidative and Al stress in wheat roots. Findings of this study establishes a theoretical foundation for using microbial metabolites to mitigate Al toxicity in acidic soils, highlighting their potential in sustainable agriculture.
微生物次生代谢物在植物-微生物相互作用中起着至关重要的作用，调节植物的生长和应激反应。在本研究中，我们发现，许多微生物分泌的脯氨酸环状二肽环(-Phe-Pro)通过增加根的生长、减少几丁质的沉积和降低 Al 积累，来缓解小麦根中的铝毒性。环(-Phe-Pro)还显著降低了铝诱导的活性氧（ROS），根尖端的 H2O2、O2 和 •OH 水平分别降低了 19.1%、42.8%和 17.9%，从而保护质膜免受氧化损伤。尽管铝胁迫增加了小麦根中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）和抗坏血酸过氧化物酶（APX）的活性，但环(-Phe-Pro)的应用降低了这些酶的活性。然而，与铝处理相比，环(-Phe-Pro)的应用使小麦根中的 DPPH 和 FRAP 活性分别增加了 16.8%和 14.9%，表明小麦根中的非酶抗氧化能力增强。我们观察到铝导致抗坏血酸（AsA）和谷胱甘肽（GSH）氧化为脱氢抗坏血酸（DHA）和谷胱甘肽二硫化物（GSSG）。在铝胁迫下，环(-Phe-Pro)处理维持了小麦根中还原型 AsA 和 GSH 的水平，以及高的 AsA/DHA 和 GSH/GSSG 氧化还原对比值。高的 AsA/DHA 和 GSH/GSSG 比值可以通过抗氧化特性来中和自由基和恢复氧化还原平衡，从而减轻铝毒性。这些结果表明，环(-Phe-Pro)通过维持依赖于 AsA 和 GSH 的氧化还原平衡来缓解小麦根中的氧化和铝胁迫。本研究的结果为利用微生物代谢物来缓解酸性土壤中的铝毒性奠定了理论基础，突出了它们在可持续农业中的应用潜力。
