Processing of ATG8s, ubiquitin-like proteins, and their deconjugation by ATG4s are essential for plant autophagy
Processing of ATG8s, ubiquitin-like proteins, and their deconjugation by ATG4s are essential for plant autophagy
复制标题
DOI：
10.1105/tpc.104.025395
复制
发表时间：
2004-11-01
期刊：
影响因子：
11.6
通讯作者：
Ohsumi, Y
中科院分区：
文献类型：
--
作者：
Yoshimoto, K;Hanaoka, H;Ohsumi, Y
自噬是细胞内细胞质成分的空泡降解过程。到目前为止，植物自噬的研究主要是使用形态学分析。最近的一项全基因组搜索发现，酵母和植物中的自噬基因（ATG）具有显著的保守性。然而，尚未证明拟南芥ATG基因是植物自噬所必需的。为了评估这一要求，我们研究了泛素化样Atg 8脂化系统，其组成基因都存在于拟南芥基因组中。在拟南芥中，所有9个ATG 8基因和两个ATG 4基因的表达无处不在，并进一步诱导氮饥饿。为了建立一个系统监测整个植物中的自噬，我们产生了转基因拟南芥表达每一个绿色荧光蛋白-ATG 8融合（GFP-ATG 8）。在野生型植物中，观察到GFP-ATG 8在细胞质中呈环形，并在氮饥饿条件下被递送到液泡腔。相比之下，在ATG 4s的T-DNA插入双突变体（atg 4a 4 b-1）中，没有观察到自噬体，并且在氮饥饿条件下GFP-ATG 8没有被递送到液泡。此外，我们检测到自噬体的空泡中的野生型根，但不是在那些atg 4a 4 b-1的存在下的concanamycin A，V-ATP酶抑制剂。生化分析也提供了证据，高等植物中的自噬需要ATG蛋白。atg 4a 4 b-1的表型分析表明，在营养限制条件下，植物自噬有助于根系的发育。
Autophagy is an intracellular process for vacuolar degradation of cytoplasmic components. Thus far, plant autophagy has been studied primarily using morphological analyses. A recent genome-wide search revealed significant conservation among autophagy genes (ATGs) in yeast and plants. It has not been proved, however, that Arabidopsis thaliana ATG genes are required for plant autophagy. To evaluate this requirement, we examined the ubiquitination-like Atg8 lipidation system, whose component genes are all found in the Arabidopsis genome. In Arabidopsis, all nine ATG8 genes and two ATG4 genes were expressed ubiquitously and were induced further by nitrogen starvation. To establish a system monitoring autophagy in whole plants, we generated transgenic Arabidopsis expressing each green fluorescent protein-ATG8 fusion (GFP-ATG8). In wild-type plants, GFP-ATG8s were observed as ring shapes in the cytoplasm and were delivered to vacuolar lumens under nitrogen-starved conditions. By contrast, in a T-DNA insertion double mutant of the ATG4s (atg4a4b-1), autophagosomes were not observed, and the GFP-ATG8s were not delivered to the vacuole under nitrogen-starved conditions. In addition, we detected autophagic bodies in the vacuoles of wild-type roots but not in those of atg4a4b-1 in the presence of concanamycin A, a V-ATPase inhibitor. Biochemical analyses also provided evidence that autophagy in higher plants requires ATG proteins. The phenotypic analysis of atg4a4b-1 indicated that plant autophagy contributes to the development of a root system under conditions of nutrient limitation.