Deg1 protease functions in protease and chaperone of PSII complex components, but few works were performed to study the effects of Deg1 on electron transport activities on the donor and acceptor side of PSII and its correlation with the photoprotection of PSII during photoinhibition. Therefore, we performed systematic and comprehensive investigations of electron transfers on the donor and acceptor sides of photosystem II (PSII) in the Deg1-reduced transgenic lines deg1-2 and deg1-4. Both the maximal quantum efficiency of PSII photochemistry (F_v/F_m) and the actual PSII efficiency (Φ_PSII) decreased significantly in the transgenic plants. Increases in nonphotochemical quenching (NPQ) and the dissipated energy flux per reaction center (DI₀/RC) were also shown in the transgenic plants. Along with the decreased D1, CP47, and CP43 content, these results suggested photoinhibition under growth light conditions in transgenic plants. Decreased Deg1 caused inhibition of electron transfer on the PSII reducing side, leading to a decline in the number of Q_B-reducing centers and accumulation of Q_B-nonreducing centers. The Tm of the Q band shifted from 5.7 °C in the wild-type plant to 10.4 °C and 14.2 °C in the deg1-2 and deg1-4 plants, respectively, indicating an increase in the stability of S₂Q_A^¯ in transgenic plants. PSIIα in the transgenic plants largely reduced, while PSIIβ and PSIIγ increased with the decline in the Deg1 levels in transgenic plants suggesting PSIIα centers gradually converted into PSIIβ and PSIIγ centers in the transgenic plants. Besides, the connectivity of PSIIα and PSIIβ was downregulated in transgenic plants. Our results reveal that downregulation of Deg1 protein levels induced photoinhibition in transgenic plants, leading to loss of PSII activities on both the donor and acceptor sides in transgenic plants. These results give a new insight into the regulation role of Deg1 in PSII electron transport.

Deg1 蛋白酶在 PSII 复合组分的蛋白酶和伴侣蛋白中发挥作用，但很少有工作研究 Deg1 对 PSII 供体和受体侧电子传递活性的影响及其与 PSII 在光抑制过程中的光保护作用的相关性。因此，我们对 Deg1 减少的转基因系deg1-2和deg1-4中光系统 II (PSII) 的供体和受体侧的电子转移进行了系统和全面的研究。PSII 光化学的最大量子效率 (F _v /F _m ) 和实际 PSII 效率 (Φ _PSII) 在转基因植物中显着降低。转基因植物中也显示了非光化学猝灭 (NPQ) 和每个反应中心耗散能量通量 (DI _{0 /RC) 的增加。}随着 D1、CP47 和 CP43 含量的降低，这些结果表明转基因植物在生长光照条件下存在光抑制。降低的Deg1 会抑制PSII 还原侧的电子转移，导致Q B 还原中心的数量减少和Q _B非还原中心的积累。Q 波段的Tm从野生型植物的 5.7 °C 转变为deg1-2和deg1-4的 10.4 °C 和 14.2 °C植物，分别表明转基因植物中 S ² Q _A的_{稳定性增加。}转基因植物中的PSIIα大大减少，而PSIIβ和PSIIγ随着转基因植物中Deg1水平的下降而增加，表明PSIIα中心逐渐转变为转基因植物中的PSIIβ和PSIIγ中心。此外，PSIIα和PSIIβ的连接性在转基因植物中被下调。我们的研究结果表明，Deg1 蛋白水平的下调诱导转基因植物的光抑制，导致转基因植物中供体和受体两侧的 PSII 活性丧失。这些结果对 Deg1 在 PSII 电子传输中的调节作用提供了新的见解。