Department of General Botany, Institute of Experimental Biology, Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614, Poznań, Poland.
Department of Virology and Bacteriology, Institute of Plant Protection-National Research Institute, Wł. Węgorka 20, 60-318, Poznań, Poland.
Planta. 2019 Dec;250(6):1789-1801. doi: 10.1007/s00425-019-03265-5. Epub 2019 Aug 26.
Autophagy is involved in developmentally programmed cell death and is identified during the early development of phloem, as well as xylem with a dual role, as both an inducer and executioner of cell death. The regulation of primary and secondary development of roots and stems is important for the establishment of root systems and for the overall survival of trees. The molecular and cellular basis of the autophagic processes, which are used at distinct moments during the growth of both organs, is crucial to understand the regulation of their development. To address this, we use Populus trichocarpa seedlings grown in a rhizotron system to examine the autophagy processes involved in root and stem development. To monitor the visual aspects of autophagy, transmission electron microscopy (TEM) and immunolocalization of AuTophaGy-related protein (ATG8) enabled observations of the phenomenon at a structural level. To gain further insight into the autophagy process at the protein and molecular level, we evaluated the expression of ATG gene transcripts and ATG protein levels. Alternations in the expression level of specific ATG genes and localization of ATG8 proteins were observed during the course of root or stem primary and secondary development. Specifically, ATG8 was present in the cells exhibiting autophagy, during the differentiation and early development of xylem and phloem tissues, including both xylary and extraxylary fibers. Ultrastructural observations revealed tonoplast invagination with the formation of autophagic-like bodies. Additionally, the accumulation of autophagosomes was identifiable during the differentiation of xylem in both organs, long before the commencement of cell death. Taken together, these results provide evidence in support of the dual role of autophagy in developmental PCD. A specific role of the controller of cell death, which is a committed step with the release of hydrolytic enzymes from the vacuole and final digestion of protoplast, from which there is no return once initiated, is only attributed to mega-autophagy.
自噬参与发育程序性细胞死亡，并在韧皮部和木质部的早期发育过程中被识别，木质部具有双重作用，既是细胞死亡的诱导剂又是执行者。根和茎的初生和次生发育的调节对于根系的建立和树木的整体生存至关重要。自噬过程的分子和细胞基础对于理解其发育的调节至关重要，这些过程在两个器官的生长过程中的不同时刻被使用。为了解决这个问题，我们使用在根管系统中生长的杨属黑杨幼苗来检查参与根和茎发育的自噬过程。为了监测自噬的视觉方面，透射电子显微镜（TEM）和 AuTophaGy 相关蛋白（ATG8）的免疫定位使我们能够在结构水平上观察到该现象。为了在蛋白质和分子水平上进一步深入了解自噬过程，我们评估了 ATG 基因转录物和 ATG 蛋白水平的表达。在根或茎的初生和次生发育过程中，观察到特定 ATG 基因的表达水平的变化和 ATG8 蛋白的定位。具体来说，在木质部和韧皮部组织的分化和早期发育过程中，包括木质部纤维和额外木质部纤维中，存在自噬的细胞中存在 ATG8。超微结构观察显示，质膜内陷形成自噬体样体。此外，在两个器官的木质部分化过程中，早在细胞死亡开始之前，就可以识别到自噬体的积累。总之，这些结果为自噬在发育性 PCD 中的双重作用提供了证据。细胞死亡控制器的特定作用，即从液泡释放水解酶并最终消化原生质体的决定性步骤，一旦开始就无法逆转，仅归因于巨自噬。
