Potassium (K⁺) exerts key physiological functions such as osmoregulation, stomatal movement, membrane transport, protein synthesis and photosynthesis among others. Previously, it was demonstrated in Arabidopsis thaliana that the loss of function of the chloroplast K⁺ Efflux Antiporters KEA1 and KEA2, located in the inner envelope membrane, provokes inefficient photosynthesis. Therefore, the main goal of this study was to evaluate the potential impact of the loss of function of those cation transport systems in the metabolism of reactive oxygen and nitrogen species (ROS and RNS). Using 14-day-old seedlings from Arabidopsis double knock-out kea1kea2 mutants, ROS metabolism and NO content in roots and green cotyledons were studied at the biochemical level. The loss of function of AtKEA1 and AtKEA2 did not cause oxidative stress but it provoked an alteration of the ROS homeostasis affecting some ROS-generating enzymes. These included glycolate oxidase (GOX) and NADPH-dependent superoxide generation activity, enzymatic and non-enzymatic antioxidants and both NADP-isocitrate dehydrogenase and NADP-malic enzyme activities. NO content, analyzed by confocal laser scanning microscopy (CLSM), was negatively affected in both photosynthetic and non-photosynthetic organs in kea1kea2 mutant seedlings. Furthermore, the S-nitrosoglutathione reductase (GSNOR) protein expression and activity were downregulated in kea1kea2 mutants, whereas the tyrosine nitrated protein profile, analyzed by immunoblot, was unaffected but the relative expression of each immunoreactive band changed. Moreover, kea1kea2 mutants showed an increased photorespiratory pathway and stomata closure, thus promoting a higher resilience to drought stress. Data suggest that the chloroplast osmotic balance and integrity maintained by AtKEA1 and AtKEA2 are necessary to keep the balance of ROS/RNS metabolism. Moreover, these data open new questions about how endogenous NO generation might be affected by the K⁺/H⁺ transport located in the chloroplasts.

钾（K ⁺）发挥关键的生理功能，例如渗透压调节，气孔运动，膜转运，蛋白质合成和光合作用。此前，它在已证实的拟南芥其的叶绿体功能的丧失ķ ⁺ È fflux甲ntiporters KEA1和KEA2，位于内包络膜，引发效率低光合作用。因此，本研究的主要目的是评估这些阳离子转运系统功能丧失对活性氧和氮物质（ROS和RNS）代谢的潜在影响。使用来自拟南芥14天龄双敲除kea1kea2的幼苗在生化水平上研究了突变体，根和绿色子叶中的ROS代谢和NO含量。AtKEA1和AtKEA2功能的丧失并不会引起氧化应激，但会引起ROS稳态的改变，从而影响某些产生ROS的酶。这些包括乙醇酸氧化酶（GOX）和NADPH依赖的超氧化物生成活性，酶和非酶抗氧化剂以及NADP-异柠檬酸脱氢酶和NADP-苹果酸酶的活性。通过共聚焦激光扫描显微镜（CLSM）分析，在kea1kea2突变体幼苗的光合器官和非光合器官中，NO含量均受到不利影响。此外，kea1kea2中的S-亚硝基谷胱甘肽还原酶（GSNOR）蛋白表达和活性下调。突变体，而通过免疫印迹分析的酪氨酸硝酸化蛋白质谱未受影响，但每个免疫反应带的相对表达均发生了变化。此外，kea1kea2突变体显示出增加的光呼吸途径和气孔关闭，从而促进了对干旱胁迫的较高抵御力。数据表明，AtKEA1和AtKEA2维持的叶绿体渗透平衡和完整性对​​于保持ROS / RNS代谢的平衡是必要的。而且，这些数据提出了新的问题，即叶绿体中的K ⁺ / H ⁺转运如何影响内源性NO的产生。