Institut Agro, University of Angers INRAE, IRHS, SFR QUASAV, F-49000 Angers, France.
Plant Physiol. 2021 Jun 11;186(2):910-928. doi: 10.1093/plphys/kiab123.
Rosebush (Rosa "Radrazz") plants are an excellent model to study light control of bud outgrowth since bud outgrowth only arises in the presence of light and never occurs in darkness. Recently, we demonstrated high levels of hydrogen peroxide (H2O2) present in the quiescent axillary buds strongly repress the outgrowth process. In light, the outgrowing process occurred after H2O2 scavenging through the promotion of Ascorbic acid-Glutathione (AsA-GSH)-dependent pathways and the continuous decrease in H2O2 production. Here we showed Respiratory Burst Oxidase Homologs expression decreased in buds during the outgrowth process in light. In continuous darkness, the same decrease was observed although H2O2 remained at high levels in axillary buds, as a consequence of the strong inhibition of AsA-GSH cycle and GSH synthesis preventing the outgrowth process. Cytokinin (CK) application can evoke bud outgrowth in light as well as in continuous darkness. Furthermore, CKs are the initial targets of light in the photocontrol process. We showed CK application to cultured buds in darkness decreases bud H2O2 to a level that is similar to that observed in light. Furthermore, this treatment restores GSH levels and engages bud burst. We treated plants with buthionine sulfoximine, an inhibitor of GSH synthesis, to solve the sequence of events involving H2O2/GSH metabolisms in the photocontrol process. This treatment prevented bud burst, even in the presence of CK, suggesting the sequence of actions starts with the positive CK effect on GSH that in turn stimulates H2O2 scavenging, resulting in initiation of bud outgrowth.
野蔷薇（Rosa“Radrazz”）植株是研究光控制芽生长的极好模型，因为芽生长仅在光照下发生，而在黑暗中从不发生。最近，我们证明了在休眠的腋芽中存在高水平的过氧化氢（H2O2）强烈抑制芽的生长过程。在光照下，通过促进抗坏血酸-谷胱甘肽（AsA-GSH）依赖性途径和持续减少 H2O2 产生，H2O2 被清除后，出芽过程发生。在这里，我们发现呼吸爆发氧化酶同源物（Respiratory Burst Oxidase Homologs）在光照下芽生长过程中的表达降低。在连续黑暗中，尽管 H2O2 仍保持在腋芽中的高水平，由于 AsA-GSH 循环和 GSH 合成的强烈抑制阻止了芽的生长过程，也观察到相同的降低。细胞分裂素（CK）的应用可以在光照下以及连续黑暗中引发芽的生长。此外，CK 是光控过程中光的初始靶标。我们表明，将 CK 应用于黑暗中的培养芽可将芽中的 H2O2 降低到与光照下观察到的相似水平。此外，这种处理恢复了 GSH 水平并引发了芽的萌发。我们用丁硫氨酸亚砜胺（一种 GSH 合成抑制剂）处理植物，以解决光控过程中涉及 H2O2/GSH 代谢的事件顺序。该处理阻止了芽的萌发，即使存在 CK，这表明作用顺序始于 CK 对 GSH 的正向作用，继而刺激 H2O2 的清除，从而启动芽的生长。
