黑松感染松材线虫后细胞结构变化及PCD

Ultrastructural changes and PCD characteristics of Pinus thunbergii cells after being infected by Bursaphelenchus xylophilus

电镜观察到两年生黑松感染松材线虫后,茎中形成层细胞以及其他的薄壁细胞出现细胞程序性死亡PCD特征:细胞核变形、核染色质浓缩并边缘化;细胞质和液泡中出现大量环状片层及多泡体;细胞壁出现膨胀扭曲;线粒体峭数目减少直至双层膜破毁.在整个变化过程中,细胞质膜始终是完整的,内质网在细胞器降解过程中扮演了重要角色,细胞核在线粒体等细胞器降解之后才崩塌消失.这表明,黑松感染松材线虫后的系统反应过程中有PCD发生,其变化类似于动物细胞中的细胞死亡.黑松感染松材线虫后的系统反应过程中,PCD是持续发生的,最终引起植株全面崩溃,这可能是感病黑松死亡的内因.在感病10d后,形成层区才开始出现空洞化现象.因此,形成层的空洞化并非是植株死亡的主因,而是其感病症状.

To investigate the involvement of programmed cell death(PCD) in systematic response, Pinus thunbergii cells infected with Bursaphelenchus xylophilus were studied. After inoculation with B. xylophilus on P. thunbergii stem from two-year-old seedlings, the structure of stem cells was studied with transmission electron microscope. The results showed that vascular cambium cells and other parenchyma cells displayed PCD characteristics: the nuclei gradually became irregular with highly condensed chromatin and stayed at the edge of cells. There were abundant annulate lamellae and phenolics, multrvesicle bodies in cell plasma and tonoplast, and the cell wall was swollen. The cristae of mitochondria became fewer, double layer membrane of mitochondria was broken at last. In the whole process, the plasmalemma still was intact, endoplasmic reticulum and vacuoles played a vital role in the further degeneration of other organelles and the nuclear collapsed at the last stage. These results demonstrated that PCD was involved in the process of systematic response, and the formation of PCD in cells might be similar to cytoplasmic cell death in animal cells. In addition, ten days later after the tree was infected with B. xylophilus,the cavitation formed in cambium zone.Therefore,cavitation in the cambium zone is not the main reason of plant death,but the symptom of being infected.