超低温保存后玉兰花粉的氧化应激和细胞凋亡研究

Oxidative Stress and/or Apoptosis of Magnolia denudata Pollen after Cryopreservation

为了揭示花粉超低温保存的生理机制,本研究以玉兰花粉作为试验材料,对花粉超低温保存前后与氧化应激和细胞凋亡相关的指标进行测定。结果显示,活性氧水平和丙二醛含量在花粉超低温保存前后没有显著变化,而质膜相对透性在超低温保存后显著提高,说明脂质过氧化不是造成细胞膜通透性增强的直接原因。超低温保存后过氧化氢酶活性显著升高,而抗坏血酸含量显著下降,说明超低温保存引起了玉兰花粉细胞内抗氧化防御系统的显著变化,细胞通过氧化/抗氧化系统的自我调节取得了新的平衡,因而使活性氧的水平在保存前后维持了稳定,并未诱导氧化应激的发生。对磷脂酰丝氨酸的外化水平和DNA片段化程度的测定表明,超低温保存并未引起细胞凋亡现象的发生。这可能是维持超低温保存后玉兰花粉高生活力的根本原因。

In order to reveal the physiological mechanism of pollen cryopreservation, pollen of Magnolia denudata was chosen and the oxidative stress and apoptosis-related indicators were measured. The results showed that there was no significant difference on reactive oxygen species generation and malonic dialdehyde content, whereas significan tly increase was observed on relative conductivity, which indicated that lipid peroxidation was not a direct cause for enhanced membrane permeability. Significant increase on catalase activity and obvious decrease on ascorbic acid content were discovered, which suggested that cryopreservation had caused a significant change in antioxidant defense system of the magnolia pollen cell and a new balance had achieved via self-regulation of oxidant/antioxidants system, resulted in nonsignificant change on reactive oxygen species generation and no oxidative stress occurred. The results on phosphatidylserine externalization and DNA ladder measurements revel that apoptosis did not exist in magnolia pollen cryopre servation. These may be the reasons why high germination level of pollen was remained after cryopreservation.