The plastid terminal oxidase (PTOX) has been shown to be an important sink for photosynthetic electron transport in stress-tolerant plants. However, overexpression studies in stress-sensitive species have previously failed to induce significant activity of this protein. Here we show that overexpression of PTOX from the salt-tolerant brassica species Eutrema salsugineum does not, alone, result in activity, but that overexpressing plants show faster induction and a greater final level of PTOX activity once exposed to salt stress. This implies that an additional activation step is required before activity is induced. We show that that activation involves the translocation of the protein from the unstacked stromal lamellae to the thylakoid grana and a protection of the protein from trypsin digestion. This represents an important activation step and opens up possibilities in the search for stress-tolerant crops.

质体末端氧化酶 (PTOX) 已被证明是耐胁迫植物中光合电子传递的重要汇。然而，在压力敏感物种中的过表达研究以前未能诱导这种蛋白质的显着活性。在这里，我们展示了耐盐芸苔属物种Eutrema salsugineum中 PTOX 的过表达单独并不会导致活性，但过度表达的植物一旦暴露于盐胁迫，就会表现出更快的诱导和更高的 PTOX 活性最终水平。这意味着在诱导活动之前需要额外的激活步骤。我们表明，这种激活涉及蛋白质从未堆叠的基质薄片转移到类囊体颗粒，并保护蛋白质免受胰蛋白酶消化。这代表了一个重要的激活步骤，并为寻找耐胁迫作物开辟了可能性。