Institute of Plant Nutritional Physiology and Molecular Biology, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Institute of Materia Medica, Fujian Academy of Medical Sciences, Fuzhou 350001, China.
Ecotoxicol Environ Saf. 2018 Aug 30;158:213-222. doi: 10.1016/j.ecoenv.2018.04.038. Epub 2018 Apr 25.
Little is known about the physiological and molecular responses of leaves to aluminum (Al)-toxicity. Seedlings of Al-intolerant Citrus grandis and Al-tolerant Citrus sinensis were supplied daily with nutrient solution containing 0 mM (control) and 1.0 mM (Al-toxicity) AlCl·6HO for 18 weeks. We found that Al-treatment only decreased CO assimilation in C. grandis leaves, and that the Al-induced alterations of gene expression profiles were less in C. sinensis leaves than those in C. grandis leaves, indicating that C. sinensis seedlings were more tolerant to Al-toxicity than C. grandis ones. Al concentration was similar between Al-treated C. sinensis and C. grandis roots, but it was higher in Al-treated C. grandis stems and leaves than that in Al-treated C. sinensis stems and leaves. Al-treated C. sinensis seedlings accumulated relatively more Al in roots and transported relatively little Al to shoots. This might be responsible for the higher Al-tolerance of C. sinensis. Further analysis showed that the following several aspects might account for the higher Al-tolerance of C. sinensis, including: (a) Al-treated C. sinensis leaves had higher capacity to maintain the homeostasis of energy and phosphate, the stability of lipid composition and the integrity of cell wall than did Al-treated C. grandis leaves; (b) Al-triggered production of reactive oxygen species (ROS) and the other cytotoxic compounds was less in Al-treated C. sinensis leaves than that in Al-treated C. grandis leaves, because Al-toxicity decreased CO assimilation only in C. grandis leaves; accordingly, more upregulated genes involved in the detoxifications of ROS, aldehydes and methylglyoxal were identified in Al-treated C. grandis leaves; in addition, flavonoid concentration was increased only in Al-treated C. grandis leaves; (c) Al-treated C. sinensis leaves could keep a better balance between protein phosphorylation and dephosphorylation than did Al-treated C. grandis leaves; and (d) both the equilibrium of hormones and hormone-mediated signal transduction were greatly disrupted in Al-treated C. grandis leaves, but less altered in Al-treated C. sinensis leaves. Finally, we discussed the differences in Al-responsive genes between Citrus roots and leaves.
关于叶片对铝毒性的生理和分子响应，人们知之甚少。将不耐铝的甜橙（Citrus grandis）和耐铝的宽皮橘（Citrus sinensis）幼苗分别每天用含有 0 mM（对照）和 1.0 mM（铝毒性）AlCl·6HO 的营养液处理 18 周。我们发现，铝处理仅降低了甜橙叶片的 CO 同化，并且在宽皮橘叶片中，铝诱导的基因表达谱改变比在甜橙叶片中少，表明宽皮橘幼苗比甜橙幼苗更能耐受铝毒性。铝处理后，宽皮橘和甜橙的根中的铝浓度相似，但在铝处理的甜橙茎和叶中的铝浓度高于在铝处理的宽皮橘茎和叶中的铝浓度。铝处理后的宽皮橘幼苗在根中积累了相对较多的铝，而向地上部分转运的铝相对较少。这可能是宽皮橘耐铝性较高的原因。进一步分析表明，宽皮橘具有较高的耐铝性，可能归因于以下几个方面：（a）铝处理后的宽皮橘叶片比铝处理后的甜橙叶片具有更高的维持能量和磷酸盐内稳态、脂质组成稳定性和细胞壁完整性的能力；（b）铝处理后的宽皮橘叶片中活性氧（ROS）和其他细胞毒性化合物的产生比铝处理后的甜橙叶片少，因为铝毒性仅降低了甜橙叶片的 CO 同化；因此，在铝处理的甜橙叶片中鉴定到更多参与 ROS、醛和甲基乙二醛解毒的上调基因；此外，仅在铝处理的甜橙叶片中增加了类黄酮浓度；（c）铝处理后的宽皮橘叶片比铝处理后的甜橙叶片具有更好的蛋白磷酸化和去磷酸化之间的平衡；（d）铝处理后的甜橙叶片中激素平衡和激素介导的信号转导受到严重破坏，而在铝处理后的宽皮橘叶片中则改变较小。最后，我们讨论了柑橘根和叶中对铝响应基因的差异。
