Department of Horticulture, Zijingang Campus, Zhejiang University, Hangzhou 310058, People's Republic of China.
Zhejiang Provincial Key Laboratory of Horticultural Plant Integrative Biology, Hangzhou 310058, People's Republic of China.
Plant Physiol. 2019 Aug;180(4):2061-2076. doi: 10.1104/pp.19.00088. Epub 2019 Jun 12.
Photoprotection is an important strategy adopted by plants to avoid photoinhibition under stress conditions. However, the way in which photoprotection is regulated is not fully understood. Here, we demonstrate that tomato () mutants of brassinosteroid (BR) biosynthesis () and related signaling through BRASSINAZOLE-RESISTANT1 () are more sensitive to (PSII and PSI photoinhibition, with decreased cyclic electron flow around PSI and lower nonphotochemical quenching, accumulation of PSII subunit S (PsbS), violaxanthin deepoxidase (VDE) activity, and D1 protein abundance. Chilling induced the accumulation of active BRs and activated BZR1, which directly activates the transcription of () and hydrogen peroxide production in the apoplast. While apoplastic hydrogen peroxide is essential for the induction of PROTON GRADIENT REGULATION5 (PGR5)-dependent cyclic electron flow, PGR5 participates in the regulation of chilling- and BR-dependent induction of nonphotochemical quenching, accumulation of D1, VDE, and PsbS proteins, transcription of genes involved in redox signaling, hormone signaling, and activity of several antioxidant enzymes. Mutations in and or suppressed transcription of compromised chilling- and BR-induced photoprotection, resulting in increased sensitivity to photoinhibition. These results demonstrate that BRs act as a positive regulator of photoprotection in a redox-PGR5-dependent manner in response to chilling stress in tomato.
光保护是植物在胁迫条件下避免光抑制的一种重要策略。然而，光保护的调控方式还不完全清楚。在这里，我们证明，拟南芥油菜素内酯（BR）生物合成（）和相关信号转导的突变体通过 BRASSINAZOLE-RESISTANT1 () 对 PSII 和 PSI 光抑制更敏感，PSI 周围的循环电子流降低，非光化学猝灭降低，PSII 亚基 S (PsbS)、紫黄质脱环氧化酶 (VDE) 活性和 D1 蛋白丰度降低。冷胁迫诱导活性 BR 的积累和 BZR1 的激活，后者直接激活 () 和质外体中过氧化氢的产生的转录。虽然质外体中的过氧化氢对于诱导依赖 PROTON GRADIENT REGULATION5 (PGR5) 的循环电子流是必需的，但 PGR5 参与了冷胁迫和 BR 依赖性非光化学猝灭诱导、D1、VDE 和 PsbS 蛋白积累、参与氧化还原信号转导、激素信号转导和几种抗氧化酶活性的基因转录的调控。突变或转录抑制会削弱冷胁迫和 BR 诱导的光保护作用，导致对光抑制的敏感性增加。这些结果表明，BR 通过依赖于氧化还原的 PGR5 以一种正向的方式调节番茄应对冷胁迫时的光保护作用。
