Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China.
Plant Biol (Stuttg). 2013 Nov;15(6):1033-9. doi: 10.1111/j.1438-8677.2012.00712.x. Epub 2013 Jul 19.
Ulva prolifera, an intertidal macroalga, has to adapt to wide variations in light intensity, making this species particularly rewarding for studying the evolution of photoprotective mechanisms. Intense light induced increased non-photochemical quenching (NPQ) and stimulated de-epoxidation of xanthophyll cycle components, while DTT-treated samples had lower NPQ capacity, indicating that the xanthophyll cycle must participate in photoprotection. In this work, we found that the PsbS-related NPQ was maintained in U. prolifera. According to analysed gene expression, both LhcSR and psbS were up-regulated in high light, suggesting that these two genes are light-induced. LHCSR and PsbS proteins were present at different light intensities and accumulated under high light conditions, and PsbS concentrations were higher than LHCSR, showing that the NPQ mechanism of U. prolifera is more dependent on PsbS protein concentration. Moreover, the level of both LHCSR and PsbS proteins was high even in the darkness, and neither the transcript level nor protein content of LhcSR and psbS genes varied significantly following short-term exposure to intense light. These findings suggest that this alga can modulate NPQ levels through regulation of the xanthophyll cycle and concentrations of PsbS and/or LHCSR.
石莼，一种潮间带大型海藻，必须适应光照强度的广泛变化，因此该物种特别适合研究光保护机制的进化。强光诱导非光化学猝灭（NPQ）增加和叶黄素循环成分脱环氧化，而 DTT 处理的样品具有较低的 NPQ 能力，表明叶黄素循环必须参与光保护。在这项工作中，我们发现石莼中存在与 PsbS 相关的 NPQ。根据基因表达分析，LhcSR 和 psbS 在高光下均上调，表明这两个基因是光诱导的。LHCSR 和 PsbS 蛋白在不同的光照强度下存在，并在高光条件下积累，PsbS 浓度高于 LHCSR，表明石莼的 NPQ 机制更依赖于 PsbS 蛋白浓度。此外，LHCSR 和 PsbS 蛋白的水平即使在黑暗中也很高，LhcSR 和 psbS 基因的转录水平和蛋白含量在短时间暴露于强光下也没有明显变化。这些发现表明，这种藻类可以通过调节叶黄素循环和 PsbS 和/或 LHCSR 的浓度来调节 NPQ 水平。
