Leaf senescence and starvation-induced chlorosis are accelerated by the disruption of an Arabidopsis autophagy gene
Leaf senescence and starvation-induced chlorosis are accelerated by the disruption of an Arabidopsis autophagy gene
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DOI：
10.1104/pp.011024
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发表时间：
2002-07-01
期刊：
影响因子：
7.4
通讯作者：
Ohsumi, Y
中科院分区：
文献类型：
--
作者：
Hanaoka, H;Noda, T;Ohsumi, Y
自噬是细胞质成分空泡大量降解的细胞内过程。负责酵母和哺乳动物自噬的分子机制最近已经开始在细胞水平上被阐明，但自噬在生物水平上所起的作用尚未确定。在这项研究中，全基因组搜索显示酵母和植物自噬基因之间存在显著的保守性。发现了25个与自噬必需的12个酵母基因同源的植物基因。我们鉴定了一个在AtAPG9中插入T-DNA的拟南芥突变体，它是拟南芥中唯一的酵母Apg9(atapg9-1)的同源基因。Atapg9在每个被测试的野生型器官中转录，但在atapg9-1突变体中不转录。在氮素或碳素饥饿条件下，与野生型植株相比，atapg9-1子叶和莲座叶的黄化现象发生得更早。此外，当氮素缺乏时，atapg9-1表现出结实减少。即使在营养生长条件下，atapg9-1植株的抽苔和叶片自然衰老也是加速的。与野生型不同，衰老相关基因SEN1和YSL4在atapg9-1诱导衰老前上调。野生型AtAPG9在atapg9-1植株中的表达补充了所有这些表型。这些结果表明，自噬对于维持细胞在营养有限的条件下的活性和整个植物的有效营养利用是必要的。
Autophagy is an intracellular process for vacuolar bulk degradation of cytoplasmic components. The molecular machinery responsible for yeast and mammalian autophagy has recently begun to be elucidated at the cellular level, but the role that autophagy plays at the organismal level has yet to be determined. In this study, a genome-wide search revealed significant conservation between yeast and plant autophagy genes. Twenty-five plant genes that are homologous to 12 yeast genes essential for autophagy were discovered. We identified an Arabidopsis mutant carrying a T-DNA insertion within AtAPG9, which is the only ortholog of yeast Apg9 in Arabidopsis (atapg9-1). AtAPG9 is transcribed in every wild-type organ tested but not in the atapg9-1 mutant. Under nitrogen or carbon-starvation conditions, chlorosis was observed earlier in atapg9-1 cotyledons and rosette leaves compared with wild-type plants. Furthermore, atapg9-1 exhibited a reduction in seed set when nitrogen starved. Even under nutrient growth conditions, bolting and natural leaf senescence were accelerated in atapg9-1 plants. Senescence-associated genes SEN1 and YSL4 were up-regulated in atapg9-1 before induction of senescence, unlike in wild type. All of these phenotypes were complemented by the expression of wild-type AtAPG9 in atapg9-1 plants. These results imply that autophagy is required for maintenance of the cellular viability under nutrient-limited conditions and for efficient nutrient use as a whole plant.