Abstract Hydrogen sulfide (H2S) and Hydrogen peroxide (H2O2) are two crucial gaseous signaling molecules that participate in various physiological processes and abiotic stresses. However, how the synergy of H2S and H2O2 regulates photosynthesis have rarely been studied. This study aimed to reveal the mechanism underlying the interaction between H2S and H2O2 in plants response to photosynthesis. Cucumber (Cucumis sativus L., ‘Jinyou 35’) seedlings were used as the material and grown in a climate chamber at 26 °C/18 °C with a 600 μmol m−2·s-1 photon flux density (PFD). Sodium hydrosulfide hydrate (NaHS, an H2S donor), H2O2, and their scavengers or inhibitors were applied as foliar sprayed at the two-leaf seedling stage. The result showed that both NaHS and H2O2 increased the CO2 assimilation, which mainly attributed to an increase in the activity and gene expression of photosynthetic enzymes. NaHS and H2O2 also induced photoprotection for both photosystem Ⅱ (PSⅡ) and photosystem Ⅰ (PSⅠ) in cucumber seedlings, by activating the D1 protein repair pathway under chilling stress. Interestingly, 1.0 mM NaHS significantly enhanced the relative gene expression of respiratory burst oxidase homolog (RBOH), which in turn elevated endogenous H2O2 accumulation in cucumber seedlings. However, H2O2 had little effect on gene expression of L-/D-cysteine desulfhydrase (L-/D-CD) and endogenous H2S level. The H2S-induced adaptive response of photosynthesis to chilling stress was suppressed by diphenyleneiodonium (DPI, a H2O2 generation inhibitor) or dimethylthiourea (DMTU, a H2O2 scavenger). These data suggest that NaHS alleviates the negative effects of chilling stress on photosynthesis by improving photosynthetic carbon assimilation, carbon metabolism, and photoprotection for both PSⅡ and PSⅠ in cucumber seedlings. H2O2 may act as a downstream signal in H2S-induced protection of the photosynthetic apparatus in cucumber seedlings under chilling stress.

中文翻译：

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过氧化氢参与硫化氢诱导的黄瓜幼苗碳同化和光保护

摘要 硫化氢 (H2S) 和过氧化氢 (H2O2) 是两种重要的气体信号分子，参与各种生理过程和非生物胁迫。然而，很少有人研究 H2S 和 H2O2 的协同作用如何调节光合作用。本研究旨在揭示植物对光合作用响应中 H2S 和 H2O2 相互作用的潜在机制。黄瓜 (Cucumis sativus L., 'Jinyou 35') 幼苗被用作材料并在气候室中在 26 °C/18 °C 下生长，光子通量密度 (PFD) 为 600 μmol m-2·s-1。水合氢硫化钠（NaHS，H2S 供体）、H2O2 及其清除剂或抑制剂在两叶苗期叶面喷施。结果表明 NaHS 和 H2O2 都增加了 CO2 同化，这主要归因于光合酶活性和基因表达的增加。NaHS和H2O2还通过在低温胁迫下激活D1蛋白修复途径，对黄瓜幼苗中的光系统Ⅱ（PSⅡ）和光系统Ⅰ（PSⅠ）产生光保护作用。有趣的是，1.0 mM NaHS 显着增强了呼吸爆发氧化酶同源物 (RBOH) 的相关基因表达，从而提高了黄瓜幼苗中内源性 H2O2 的积累。然而，H2O2 对 L-/D-半胱氨酸脱硫酶 (L-/D-CD) 的基因表达和内源性 H2S 水平几乎没有影响。H2S 诱导的光合作用对低温胁迫的适应性反应受到二亚苯基碘鎓（DPI，H2O2 生成抑制剂）或二甲基硫脲（DMTU，H2O2 清除剂）的抑制。这些数据表明NaHS通过改善黄瓜幼苗PSⅡ和PSⅠ的光合碳同化、碳代谢和光保护，减轻了低温胁迫对光合作用的负面影响。H2O2 可能在 H2S 诱导的低温胁迫下黄瓜幼苗的光合器官保护中充当下游信号。