Shen Yu, Li Jinfeng, Gu Ruochen, Yue Le, Zhan Xinhua, Xing Baoshan
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, People's Republic of China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, United States.
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, People's Republic of China.
Environ Pollut. 2017 Jan;220(Pt B):1311-1321. doi: 10.1016/j.envpol.2016.11.003. Epub 2016 Nov 9.
Leaf is an important organ in responding to environmental stresses. To date, chlorophyll metabolism under polycyclic aromatic hydrocarbon (PAH) stress is still unclear. Here we reveal, for the first time, the chlorophyll metabolism of wheat seedling leaves in response to phenanthrene (a model PAH) exposure. In this study, the hydroponic experiment was employed, and the wheat seedlings were exposed to phenanthrene to observe the response at day 1, 3, 5, 7 and 9. Over the exposure time, wheat leaf color turns light. With the accumulation of phenanthrene, the concentrations of glutamate, 5-aminolevulinic acid, uroporphyrinogen III, protoporphyrin IX, Mg-protoporphyrin IX and protochlorophyllide increase while the concentrations of porphobilinogen and Chlorophyll b decrease. Also chlorophyll a content rises initially and then declines. Uroporphyrinogen III synthase and chlorophyllase are activated and porphobilinogen deaminase activity declines in the treatments. Both chlorophyll synthesis and degradation are enhanced, but the degradation rate is faster. Phenanthrene accumulation has significant and positive effects on increase of glutamate, 5-aminolevulinic acid, uroporphyrinogen III, protoporphyrin IX, Mg-protoporphyrin IX and protochlorophyllide concentrations. There is a negative correlation between phenanthrene accumulation and total chlorophyll. Additionally, the leaf moisture increases. Therefore, it is concluded that wheat leaf chlorosis results from a combination of accelerated chlorophyll degradation and elevated leaf moisture under phenanthrene exposure. Our results are helpful not only for better understanding the toxicity of PAHs to plants and crop PAH-adaptive mechanism in the environment, but also for potentially employing the changes of the chlorophyll-synthesizing precursors and enzyme activities in plant leaves as indicators of plant response to PAH pollution.
叶片是植物响应环境胁迫的重要器官。迄今为止，多环芳烃（PAH）胁迫下的叶绿素代谢仍不清楚。在此，我们首次揭示了小麦幼苗叶片在菲（一种典型的PAH）暴露下的叶绿素代谢情况。本研究采用水培实验，将小麦幼苗暴露于菲中，在第1、3、5、7和9天观察其反应。在暴露期间，小麦叶片颜色变浅。随着菲的积累，谷氨酸、5-氨基乙酰丙酸、尿卟啉原III、原卟啉IX、镁原卟啉IX和原叶绿素酸酯的浓度增加，而胆色素原和叶绿素b的浓度降低。叶绿素a含量起初上升，随后下降。尿卟啉原III合酶和叶绿素酶被激活，而胆色素原脱氨酶活性在处理中下降。叶绿素的合成和降解均增强，但降解速率更快。菲的积累对谷氨酸、5-氨基乙酰丙酸、尿卟啉原III、原卟啉IX、镁原卟啉IX和原叶绿素酸酯浓度的增加具有显著的正向影响。菲的积累与总叶绿素之间呈负相关。此外，叶片含水量增加。因此，可以得出结论，在菲暴露下，小麦叶片黄化是叶绿素降解加速和叶片含水量升高共同作用的结果。我们的研究结果不仅有助于更好地理解PAHs对植物的毒性以及环境中作物对PAH的适应机制，还可能将植物叶片中叶绿素合成前体和酶活性的变化用作植物对PAH污染响应的指标。
