Selective Elimination of Membrane-Damaged Chloroplasts via Microautophagy1[OPEN]
Selective Elimination of Membrane-Damaged Chloroplasts via Microautophagy1[OPEN]
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通过微自噬选择性消除膜损伤的叶绿体1[打开]
作者：
Sakuya Nakamura;J. Hidema;W. Sakamoto;H. Ishida;M. Izumi
拟南芥自噬是一种选择性自噬过程，通过叶绿体介导的运输去除由强光诱导的膜损伤引起的肿胀叶绿体。植物叶绿体在光合作用过程中不断累积可见光波长造成的损伤。我们之前的研究表明，整个光损伤的叶绿体通过称为自噬的自噬过程受到空泡消化；然而，这个过程是如何诱导和执行的，人们仍然知之甚少。在本研究中，我们监测了拟南芥（Arabidopsis thaliana）叶片的细胞内噬绿诱导，发现在高可见光下受损的叶肉细胞显示出异常的叶绿体，形状肿胀，体积是正常叶绿体的2.5倍。在野生型植物中，自噬的激活减少了肿胀叶绿体的数量。在自噬缺陷突变体中，肿胀的叶绿体持续存在，失去叶绿素荧光的功能失调的叶绿体在细胞质中积累。通过外源甘露醇增加叶绿体外渗透压或通过过度表达VESICLE INDUCING PROTEIN IN PLASTID1来维持叶绿体包膜完整性，可以抑制叶绿体肿胀和随后的自噬诱导。自噬相关膜的显微镜观察显示，肿胀的叶绿体部分被自噬体结构包围，并直接被张力体吞没，如微自噬。我们的研究结果表明，由于可见光引起的高包膜损伤导致叶绿体内部渗透电位升高，导致叶绿体肿胀，并作为噬绿的诱导因素，这一过程通过张力体介导的隔离动员整个叶绿体，以避免功能失调的叶绿体在细胞质中积累。
Chlorophagy is a selective autophagy process that removes swollen chloroplasts caused by high light-induced membrane damage via tonoplast-mediated transport in Arabidopsis thaliana. Plant chloroplasts constantly accumulate damage caused by visible wavelengths of light during photosynthesis. Our previous study revealed that entire photodamaged chloroplasts are subjected to vacuolar digestion through an autophagy process termed chlorophagy; however, how this process is induced and executed remained poorly understood. In this study, we monitored intracellular induction of chlorophagy in Arabidopsis (Arabidopsis thaliana) leaves and found that mesophyll cells damaged by high visible light displayed abnormal chloroplasts with a swollen shape and 2.5 times the volume of normal chloroplasts. In wild-type plants, the activation of chlorophagy decreased the number of swollen chloroplasts. In the autophagy-deficient autophagy mutants, the swollen chloroplasts persisted, and dysfunctional chloroplasts that had lost chlorophyll fluorescence accumulated in the cytoplasm. Chloroplast swelling and subsequent induction of chlorophagy were suppressed by the application of exogenous mannitol to increase the osmotic pressure outside chloroplasts or by overexpression of VESICLE INDUCING PROTEIN IN PLASTID1, which maintains chloroplast envelope integrity. Microscopic observations of autophagy-related membranes showed that swollen chloroplasts were partly surrounded by autophagosomal structures and were engulfed directly by the tonoplast, as in microautophagy. Our results indicate that an elevation in osmotic potential inside the chloroplast due to high visible light-derived envelope damage results in chloroplast swelling and serves as an induction factor for chlorophagy, and this process mobilizes entire chloroplasts via tonoplast-mediated sequestering to avoid the cytosolic accumulation of dysfunctional chloroplasts.
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DOI：
10.1073/pnas.061500998
发表时间：
2001-03-27
影响因子：
11.1
作者：
Kroll, D;Meierhoff, K;Westhoff, P
通讯作者：
Westhoff, P
植物自噬的新进展：调节，选择性和功能。
影响因子：
7.3
作者：
Wang P;Mugume Y;Bassham DC
通讯作者：
Bassham DC
影响因子：
11.8
作者：
Anding AL;Baehrecke EH
通讯作者：
Baehrecke EH
影响因子：
56.9
作者：
Kohler, RH;Cao, J;Hanson, MR
通讯作者：
Hanson, MR