Chlorophyll (Chl) and effective photoprotective mechanism are important prerequisites to ensure the photosynthetic function of plants under stress. In this study, the effects of 100 mmol L-1 NaCl and NaHCO3 stress on chlorophyll synthesis and photosynthetic function of mulberry seedlings were studied by physiological combined with proteomics technology. The results show that: NaCl stress had little effect on the expression of Chl synthesis related proteins, and there were no significant changes in Chl content and Chl a:b ratio. However, 13 of the 15 key proteins in the process of Chl synthesis were significantly decreased under NaHCO3 stress, and the contents of Chl a and Chl b were significantly decreased (especially Chl a). Although stomatal conductance (Gs) decreased significantly under NaCl stress, net photosynthetic rate (Pn), PSII maximum photochemical efficiency (Fv/Fm) and electron transfer rate (ETR) did not change significantly, but under NaHCO3 stress, not only Gs decreased significantly, PSII activity and photosynthetic carbon were the same. In the photoprotective mechanism under NaCl stress, NAD(P)H dehydrogenase (NDH)-dependent cyclic electron flow (CEF) enhanced, the expression of related proteins subunit, ndhH, ndhI, ndhK, and ndhM, the key enzyme of the xanthophyll cycle, violaxanthin de-epoxidase (VDE) were up-regulated, the ratio of (A + Z)/(V + A + Z) and non-photochemical quenching (NPQ) was increased. The expressions of proteins FTR and Fd-NiR were also significant up-regulated under NaCl stress, Fd-dependent ROS metabolism and nitrogen metabolism can effectively reduce the electronic pressure on Fd. Under NaHCO3 stress, the expressions of NDH-dependent CEF related proteins subunit (ndhH, ndhI, ndhK, ndhM and ndhN), VDE, ZE, FTR, Fd-NiR and Fd-GOGAT, were significant down-regulated, and ZE, CP26, ndhK, ndhM, Fd-NiR, Fd-GOGAT and FTR genes expression also significantly decreased, the photoprotective mechanism, like the xanthophyll cycle，CEF and Fd-dependent ROS metabolism and nitrogen metabolism might be damaged, resulting in the inhibition of PSII electron transfer and carbon assimilation in mulberry leaves under NaHCO3 stress.

中文翻译：

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基于TMT的蛋白质组学分析揭示了NaCl和NaHCO3胁迫下桑树幼苗叶片中的叶绿素合成及其光保护机制。

叶绿素（Chl）和有效的光保护机制是确保植物在胁迫下光合作用的重要先决条件。本研究通过生理学和蛋白质组学技术研究了100 mmol L-1 NaCl和NaHCO3胁迫对桑树幼苗叶绿素合成和光合功能的影响。结果表明：NaCl胁迫对Chl合成相关蛋白的表达影响很小，并且Chl含量和Chl a：b比率均无显着变化。然而，在NaHCO3胁迫下，Chl合成过程中的15种关键蛋白中有13种显着降低，Chla和Chlb的含量显着降低（尤其是Chla）。尽管在NaCl胁迫下气孔导度（Gs）明显降低，但净光合速率（Pn），PSII的最大光化学效率（Fv / Fm）和电子传递速率（ETR）没有明显变化，但在NaHCO3胁迫下，不仅Gs显着下降，PSII活性和光合碳均相同。在NaCl胁迫下的光保护机理中，NAD（P）H脱氢酶（NDH）依赖性循环电子流（CEF）增强，相关蛋白亚基ndhH，ndhI，ndhK和ndhM（叶黄素循环的关键酶）的表达，紫黄质脱环酶（VDE）上调，（A + Z）/（V + A + Z）和非光化学猝灭（NPQ）的比率增加。在NaCl胁迫下，FTR和Fd-NiR蛋白的表达也明显上调，Fd依赖性ROS代谢和氮代谢可以有效降低Fd的电子压力。在NaHCO3胁迫下，