Self-incompatibility (SI) is used by many angiosperms to prevent self-fertilization and inbreeding. In common poppy (Papaver rhoeas), interaction of cognate pollen and pistil S-determinants triggers programmed cell death (PCD) of incompatible pollen. We previously identified that reactive oxygen species (ROS) signal to SI-PCD. ROS-induced oxidative posttranslational modifications (oxPTMs) can regulate protein structure and function. Here, we have identified and mapped oxPTMs triggered by SI in incompatible pollen. Notably, SI-induced pollen had numerous irreversible oxidative modifications, while untreated pollen had virtually none. Our data provide a valuable analysis of the protein targets of ROS in the context of SI-induction and comprise a benchmark because currently there are few reports of irreversible oxPTMs in plants. Strikingly, cytoskeletal proteins and enzymes involved in energy metabolism are a prominent target of ROS. Oxidative modifications to a phosphomimic form of a pyrophosphatase result in a reduction of its activity. Therefore, our results demonstrate irreversible oxidation of pollen proteins during SI and provide evidence that this modification can affect protein function. We suggest that this reduction in cellular activity could lead to PCD.

许多被子植物使用自交不亲和 (SI) 来防止自我受精和近亲繁殖。在常见的罂粟（虞美人），同源花粉和雌蕊相互作用小号-决定因素触发不相容花粉的程序性细胞死亡 (PCD)。我们之前确定了活性氧 (ROS) 向 SI-PCD 发出信号。ROS 诱导的氧化翻译后修饰 (oxPTM) 可以调节蛋白质结构和功能。在这里，我们已经确定并绘制了由 SI 不相容花粉触发的 oxPTM。值得注意的是，SI 诱导的花粉具有许多不可逆的氧化修饰，而未经处理的花粉几乎没有。我们的数据在 SI 诱导的背景下对 ROS 的蛋白质靶标进行了有价值的分析，并构成了一个基准，因为目前很少有关于植物中不可逆 oxPTM 的报告。引人注目的是，参与能量代谢的细胞骨架蛋白和酶是 ROS 的重要靶点。对焦磷酸酶的磷模拟形式的氧化修饰导致其活性降低。因此，我们的结果证明了花粉蛋白在 SI 过程中的不可逆氧化，并提供了这种修饰会影响蛋白质功能的证据。我们认为这种细胞活动的减少可能导致 PCD。