异养氨氧化细菌通过双重作用机制促进多花黑麦草的再生

Heterotrophic ammonia-oxidizing bacteria promote regeneration of Italian ryegrass via a dual-action mechanism

摘要:

【背景】异养氨氧化细菌(heterotrophic ammonia-oxidizing bacteria, HAOB)通过增加叶片细胞分裂素含量促进多花黑麦草的再生，但其促进植物再生的具体机制尚未探明。【目的】揭示HAOB调控细胞分裂素的合成促进多花黑麦草再生的机制。【方法】以一株HAOB菌株(S2_8_1)为试验菌株，盆栽多花黑麦草作为植物材料。试验处理设计包括：常规供水(TA)；添加空白富集培养基(TB)；添加硝化抑制剂3,4-二甲基吡唑磷酸盐(3,4-dimethylpyrazole phosphate, DMPP) (TN1)；添加DMPP和20 mmol/L的NO₃⁻-N (TN2)；添加DMPP和30 mmol/L的NO₃⁻-N (TN3)；添加DMPP和40 mmol/L的NO₃⁻-N (TN4)；接种菌株S2_8_1 (TI)。【结果】30−40 mmol/L NO₃⁻-N对提高叶片细胞分裂素含量和根向叶片传递效果最好，从而促进叶片再生。在根际土壤硝化作用诱导的细胞分裂素增加达到最大限度时，接种菌株S2_8_1进一步增加了根中细胞分裂素的合成，提高了叶片中细胞分裂素的浓度。所测试的HAOB菌株S2_8_1通过双重作用显著提高了叶片细胞分裂素的浓度，促进了多花黑麦草再生。【结论】本研究揭示了HAOB菌株在根际发挥双重作用促进植物生长的机制，为提高牧草产量和农业可持续发展提供直接应用价值。

Abstract:

[Background] Heterotrophic ammonia-oxidizing bacteria (HAOB) promote the regeneration of Italian ryegrass by increasing the content of leaf cytokinins, although the specific mechanism remains to be elucidated. [Objective] To elucidate how HAOB promote the regeneration of Italian ryegrass by regulating the synthesis of cytokinins via a dual-action mechanism (in the rhizosphere soil and outside the rhizosphere environment, respectively. [Methods] A strain (S2_8_1) of HAOB and potted Italian ryegrass were used in this study. The treatments were designed as follows: Regular watering (TA); Addition of blank medium for enrichment culture (TB); Addition of 3,4-dimethylpyrazole phosphate (DMPP) (TN1); Addition of DMPP and 20 mmol/L NO₃⁻-N (TN2); Addition of DMPP and 30 mmol/L NO₃⁻-N (TN3); Addition of DMPP and 40 mmol/L NO₃⁻-N (TN4); Inoculation with the strain S2_8_1 (TI). [Results] NO₃⁻-N of 30–40 mmol/L was most effective in increasing the content of leaf cytokinins and enhancing the transfer of these hormones from the roots to the leaves, thereby promoting leaf regeneration. When the nitration-induced increase in cytokinins in the rhizosphere soil reached the maximum, inoculation with strain S2_8_1 further boosted the synthesis of these hormones in the roots, leading to an increased concentration of cytokinins in the leaves. The HAOB strain S2_8_1 significantly elevated the level of cytokinins in leaves via a dual-action mechanism, thereby promoting the regeneration of Italian ryegrass. [Conclusion] This study unveils the dual-action mechanism by which HAOB strains in the rhizosphere enhance plant growth, offering a direct application value for improving forage yields and sustainable agriculture development.