酸雨胁迫对尾叶桉抗逆生理及APX-类基因转录水平的影响

Effect of Physiological Indexes of Stress-resistance and Transcriptional Levels of APX-genes at Eucalyptus urophylla under Acid Rain Stress

以尾叶桉(Eucalyptus urophylla)1月龄树苗为材料,用不同pH值(5.6、4.0、2.5、2.0)的模拟酸雨连续喷雾灌根处理15 d,检测净光合速率、蒸腾速率、气孔导度、胞间二氧化碳摩尔分数、水分利用效率、叶绿素质量分数、丙二醛质量摩尔浓度、电导率、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性等生理指标及抗坏血酸过氧化物酶类基因(APX)的转录变化。酸雨处理后,叶绿素质量分数无明显变化,净光合速率、蒸腾速率、水分利用效率下降,丙二醛质量摩尔浓度、电导率显著升高,SOD活性、POD活性、CAT活性都明显升高,均在pH值为2.0有最大值,pH=2.0时,7个APX-类基因的转录水平分别为对照的1.76、2.65、3.68、7.34、0.58、1.82、1.46倍。结果表明,酸雨会抑制尾叶桉的光合作用,引起活性氧(ROS)代谢失衡,导致膜脂过氧化,且酸雨强度越大其作用越明显;SOD活性、POD活性、CAT活性增强,APX-类基因表达上调是尾叶桉应对酸雨胁迫的保护机制;抗逆生理和APX-类基因的转录水平存在对应关系。

With one-month-old seedlings of Eucalyptus urophyll, we studied the effect of acid rain on photosynthetic physiology and ROS metabolism by treating with simulative acid rain （ pH 5.6, 4.0, 2.5, 2.0） for 15 d. Then, we detected the physiology indexes related to photosynthetic physiology and ROS metabolism, and evaluated the transcriptional levels of seven APX-genes by real-time quantitative PCR. The chlorophyll content didn＇ t show obvious change, and the net photosynthetic rate, transpiration rate and water use efficiency were decreased. The malondialdehyde content and conductivity were in- creased sharply. The activities of protective enzymes, including superoxide dismutase, peroxidase and catalase were in- creased significantly and arrived to the peak at pH 2.0. The transcription activities ofAPX1, APX2, APX3, APX5, APX6, APxg, and APX10 were 1.76, 2.65, 3.68, 7.34, 0.58, 1.82 and 1.46 times higher than the control （ transcription level of the reference gene normalized to 1 ） , respectively. The acid rain inhibited photosynthesis, caused ROS metabolism imbalances, and led to membrane lipid peroxide. The raise of protective enzymes activities and APX-genes transcription strengthened the resistance to acid rain at Eucalyptus species. The physiological indexes of stress-resistance and the transcriptional levels of APX-genes had some relationships under the stress of acid rain.