Jones-Held Susan, White James F
Department of Plant Biology, Rutgers University, New Brunswick, NJ, United States.
Front Plant Sci. 2024 Dec 12;15:1480387. doi: 10.3389/fpls.2024.1480387. eCollection 2024.
Understanding the early interactions between plants and endophytes will contribute to a more systematic approach to enhancing endophyte-mediated effects on plant growth and environmental stress resistance. This study examined very early growth and ascorbate metabolism after seed treatment of with three different endophytes. The three endophytes used were pb1(Bapb1), (Ml) and SLB4 (SLB4). Seeds of cv. trophy were surface sterilized and plated on 1/2 MS Basal salts (pH 5.7 -5.8) + 0.8% agarose. Under sterile conditions, endophyte suspensions or sterile distilled water (controls) were applied to plated seeds. After two days, all plates were scanned to produce digital images for subsequent growth analysis. Then, seedlings were gently removed from the plates and placed in sterile microfuge tubes. For biochemical analyses, extracts were prepared from samples and assayed spectrophotometrically. We detected slight changes in seedling root tip and/or primary root growth with Bapb1 and Ml. Seedlings treated with SLB4 exhibited significantly increased primary root and root tip length after two days of growth. Ascorbate oxidation, however, was the primary significant change common to all endophyte-treated seedlings. In relation to ascorbate oxidation, soluble ascorbate oxidase (AO) was slightly reduced in Bapb1 and Ml-treated seedlings, whereas ionically-bound AO was reduced in Bapb1 and SLB4-treated seedlings. Total AO activity was significantly reduced in Bapb1-treated seedlings. There were no differences in cytosolic APX activity or glutathione levels between endophyte-treated seedlings and controls. Like pathogens, endophytes can trigger an oxidative burst in the plant. A level of ascorbate oxidation seems required to propagate ROS as signaling molecules as part of the plant immune response. The slight to moderate reductions in plant AO activity that we found mimic the inhibitory effects of pathogens on AO activity, but there was still a level of AO activity that may have been sufficient for the apoplastic ascorbate oxidation required for subsequent ROS signaling. Other studies have suggested that endophytes may elicit a more moderate plant immune response relative to pathogens to facilitate colonization. The AO, APX, and glutathione results would be consistent with a moderate plant immune response to endophytes.
了解植物与内生菌之间的早期相互作用，将有助于采用更系统的方法来增强内生菌介导的对植物生长和环境胁迫抗性的影响。本研究考察了用三种不同内生菌处理种子后的早期生长和抗坏血酸代谢情况。所用的三种内生菌分别是pb1（Bapb1）、（Ml）和SLB4（SLB4）。cv. trophy品种的种子进行表面灭菌后，接种在1/2 MS基础盐（pH 5.7 - 5.8）+ 0.8%琼脂糖上。在无菌条件下，将内生菌悬浮液或无菌蒸馏水（对照）施加于接种的种子上。两天后，对所有平板进行扫描以生成数字图像用于后续生长分析。然后，将幼苗从平板上轻轻取出，放入无菌微量离心管中。用于生化分析时，从样品中制备提取物并进行分光光度测定。我们检测到用Bapb1和Ml处理后，幼苗根尖和/或主根生长有轻微变化。用SLB4处理的幼苗在生长两天后，主根和根尖长度显著增加。然而，抗坏血酸氧化是所有经内生菌处理的幼苗共有的主要显著变化。关于抗坏血酸氧化，在经Bapb1和Ml处理的幼苗中，可溶性抗坏血酸氧化酶（AO）略有降低，而在经Bapb1和SLB4处理的幼苗中，离子结合型AO降低。在经Bapb1处理的幼苗中，总AO活性显著降低。经内生菌处理的幼苗与对照之间，胞质APX活性或谷胱甘肽水平没有差异。与病原体一样，内生菌可在植物中引发氧化爆发。似乎需要一定水平的抗坏血酸氧化来将ROS作为信号分子进行传播，这是植物免疫反应的一部分。我们发现植物AO活性有轻微至中度降低，这模拟了病原体对AO活性的抑制作用，但仍有一定水平的AO活性，可能足以满足后续ROS信号传导所需的质外体抗坏血酸氧化。其他研究表明，相对于病原体，内生菌可能引发更适度的植物免疫反应以促进定殖。AO、APX和谷胱甘肽的结果与植物对内生菌的适度免疫反应一致。
