Phototropins are plasma membrane-associated photoreceptors of blue light and UV-A/B radiation. The Arabidopsis thaliana genome encodes two phototropins, PHOT1 and PHOT2, that mediate phototropism, chloroplast positioning, and stomatal opening. They are well characterized in terms of photomorphogenetic processes, but so far, little was known about their involvement in photosynthesis, oxidative stress responses, and cell death. By analyzing phot1, phot2 single, and phot1phot2 double mutants, we demonstrated that both phototropins influence the photochemical and non-photochemical reactions, photosynthetic pigments composition, stomata conductance, and water-use efficiency. After oxidative stress caused by UV-C treatment, phot1 and phot2 single and double mutants showed a significantly reduced accumulation of H₂O₂ and more efficient photosynthetic electron transport compared to the wild type. However, all phot mutants exhibited higher levels of cell death four days after UV-C treatment, as well as deregulated gene expression. Taken together, our results reveal that on the one hand, both phot1 and phot2 contribute to the inhibition of UV-C-induced foliar cell death, but on the other hand, they also contribute to the maintenance of foliar H₂O₂ levels and optimal intensity of photochemical reactions and non-photochemical quenching after an exposure to UV-C stress. Our data indicate a novel role for phototropins in the condition-dependent optimization of photosynthesis, growth, and water-use efficiency as well as oxidative stress and cell death response after UV-C exposure.

中文翻译：

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Phototropin 1 和 2 影响光合作用、UV-C 诱导的光氧化应激反应和细胞死亡

Phototropins 是蓝光和 UV-A/B 辐射的质膜相关光感受器。在拟南芥基因组编码两个phototropins，PHOT1和PHOT2，介导向光性，叶绿体定位，和气孔开口。它们在光形态发生过程方面得到了很好的表征，但到目前为止，人们对它们参与光合作用、氧化应激反应和细胞死亡知之甚少。通过分析phot1、phot2 single 和phot1pht2在双突变体中，我们证明了两种向光素都会影响光化学和非光化学反应、光合色素组成、气孔导度和水分利用效率。在 UV-C 处理引起的氧化应激后，与野生型相比，phot1和phot2单突变体和双突变体显示出显着减少的 H ₂ O ₂积累和更有效的光合电子传递。然而，所有的光度计UV-C 处理四天后，突变体表现出更高水平的细胞死亡，以及基因表达失调。总之，我们的结果表明，一方面，phot1 和 phot2 都有助于抑制 UV-C 诱导的叶细胞死亡，但另一方面，它们也有助于维持叶面 H ₂ O ₂水平和暴露于 UV-C 应力后光化学反应和非光化学淬灭的最佳强度。我们的数据表明，光敏素在光合作用、生长和水分利用效率的条件相关优化以及 UV-C 暴露后的氧化应激和细胞死亡反应中发挥着新的作用。