UV-B介导光破坏防御机制及其对动态光环境下番茄种苗光合性能的影响

Plants’ capacity of acclimation under dynamic light plays a crucial role for photosynthates accumulation in nature, and a sound photoprotection mechanism is indispensable to guarantee effective operation of photosynthetic apparatus under dynamic light. It has been found that UV-B can improve photoprotection capacity, however, the process of UV-B mediates photoprotection mechanism is unclear. In this project, tomato seedlings will be selected as testing species, and UV-B will be appropriately applied to induce the formation of photoprotection mechanisms, so as to improve the adaptability of seedlings to dynamic light after transplantation. Firstly, using plant functional structure model and anatomical methods to study UV-B mediating plant phenotype and chloroplast movement, and further explore their effect on light capture under dynamic light, and clarify the response of plant light harvesting mechanism to UV-B. Secondly, based on chlorophyll a fluorescence kinetic method, study UV-B mediating energy dissipation process of photosynthetic apparatus under dynamic light. In the meanwhile, explore the network and key genes of UV-B mediated energy dissipation and UVR8 photoreceptors and downstream signaling partners through transcriptional and proteomics technology. Finally, study the effect of UV-B mediated photoprotection mechanisms on photosynthetic performance of seedlings that is transplanted to greenhouse condition. This study will be helpful to understand the physiological nature of UV-B affecting photosynthesis, and to provide a theoretical basis for horticultural seedling production.

植物适应光强波动变化的能力是决定光合产物累积的关键因素，健全的光破坏防御机制是动态光下光合机构有效运转的必要保障。研究发现UV-B可提升光破坏防御能力，但UV-B介导的光破坏防御机制形成过程还不清楚。本项目以番茄种苗为对象，拟通过UV-B处理诱导光破坏防御机制形成，从而提升种苗移植后对动态光的适应能力。首先，利用植物功能结构模型及解剖学手段，研究动态光下UV-B调控的植株表型和叶绿体运动对光截获能力的影响，阐明植物光捕获机制对UV-B的响应机理。其次，基于叶绿素a荧光动力学方法研究UV-B介导的光合机构能量耗散过程对动态光的响应；利用组学技术研究UV-B介导能量耗散过程与UVR8光受体及其下游信号伴侣的网络关系和关键基因。最后，研究UV-B介导光破坏防御机制对设施栽培条件下种苗光合性能的影响。本研究将有助于深入了解UV-B影响光合作用的生理本质，以期为设施种苗壮苗生产提供理论依据。

UVA（315-400 nm）约占自然界紫外光成分的95%，但其对植物生长的影响在很大程度上还处于未知状态。LED技术的发展为开展UVA植物光生物学研究提供了基本条件。本项目围绕UVA光环境开展了以下研究：. 1.不同波段UVA对番茄幼苗生长的影响：发现不同波段的UVA均能够有效改变番茄幼苗植株形态，促进番茄植株干物质积累，促进叶片面积、叶片厚度和叶片中叶绿素含量的增加，但对植株伸长生长的抑制作用弱于蓝光；波峰为385 nm和400 nm的UVA对酚类物质的促进作用与蓝光相似，但370nm UVA处理对酚类物质的促进作用弱于蓝光。. 2.UVA促进番茄幼苗生长的生理调控机制：发现不同剂量UVA均能促进番茄幼苗干物质积累和叶片面积增加；UVA在维持叶片光合能力方面具有与蓝光相似的功能；纯红光背景下UVA能够使番茄幼苗出现叶柄上翘和叶片平展的形态变化，提高番茄植株光截获能力，该调节作用与叶片中生长素和油菜素内脂含量上升有关。. 3.UVA对叶片形态变化的调控机制：发现370 nm UVA对叶片平展过程促进作用大于400 nm UVA，而弱蓝光对叶片展开的促进作用与较强的蓝光相同，但均弱于两种UVA处理，否定了UVA信号引起的植株形态变化与“弱蓝光”信号功能相似的假设，其形态变化也不属于避荫反应范畴。生长素运输过程被抑制后UVA和蓝光介导的叶片伸展过程消失，说明UVA与蓝光引起的叶片形态变化过程均依赖于生长素的胞间运输过程。. 4.UVA对叶片平展过程转录水平的调控机制：纯红光背景下48小时内UVA处理的叶片平展的促进作用显著高于蓝光；UVA促进了SAURs和IAA生长素响应基因表达，上调了细胞壁成分合成基因与细胞壁扩展相关基因的表达；UVA处理中未出现蓝光对赤霉素调控基因表达抑制的情况，上述调控可能是UVA对番茄幼苗特殊形态建成的调控机制。. 本研究表明370-400 nm波段的UVA能够替代蓝光信号促进植物光合系统发育，UVA介导的植株形态提高植物光截获能力。UVA作为光信号调控植物形态建成与蓝光信号不同，主要通过促进生长素信号并调控细胞壁松弛相关基因的表达来实现。