Wang Xiaoxia, Gao Yuan, Feng Yu, Li Xue, Wei Qian, Sheng Xianyong
College of Life Sciences, Capital Normal University, Beijing, China.
PLoS One. 2014 Apr 10;9(4):e94721. doi: 10.1371/journal.pone.0094721. eCollection 2014.
As one of the most severe pollutants, cadmium has been reported to be harmful to plant cells, but the effects of cadmium on gymnosperm pollen germination and tube growth and the mechanism of this involvement are still unclear. Here, we report that cadmium not only strongly inhibited P. wilsonii pollen germination and tube growth, but also significantly altered tube morphology in a dose-dependent manner. Time-lapse images obtained with a laser scanning confocal microscope revealed that endocytosis was dramatically inhibited by cadmium stress. Further investigation with ER-Tracker dye indicated that cadmium stress reduced the number of the Golgi apparatus, and induced dilation of ER. Additionally, Lyso-Tracker staining showed that cadmium distinctly promoted the formation of acidic organelles in pollen tubes, likely derived from the dilated ER. Taken together, our studies indicated that P. wilsonii pollens were highly susceptible to cadmium stress, and that cadmium stress strongly inhibited pollen germination and tube growth by disrupting the endomembrane organelles, inhibiting endo/exocytosis, and forming acidic vacuoles, resulting in swollen tube tips and irregularly broadened tube diameters. These findings provide a new insight into the effects of cadmium toxicity on the tip growth of pollen tubes.
作为最严重的污染物之一，镉已被报道对植物细胞有害，但镉对裸子植物花粉萌发和花粉管生长的影响及其作用机制仍不清楚。在此，我们报道镉不仅强烈抑制了白皮松花粉萌发和花粉管生长，还以剂量依赖的方式显著改变了花粉管形态。通过激光扫描共聚焦显微镜获得的延时图像显示，镉胁迫显著抑制了内吞作用。用内质网（ER）追踪染料进一步研究表明，镉胁迫减少了高尔基体的数量，并诱导了内质网扩张。此外，溶酶体追踪染料染色显示，镉明显促进了花粉管中酸性细胞器的形成，这些酸性细胞器可能源自扩张的内质网。综上所述，我们的研究表明白皮松花粉对镉胁迫高度敏感，镉胁迫通过破坏内膜细胞器、抑制内吞/外排作用以及形成酸性液泡，强烈抑制花粉萌发和花粉管生长，导致花粉管顶端肿胀和直径不规则增宽。这些发现为镉毒性对花粉管顶端生长的影响提供了新的见解。
