Autophagy-deficient Schizosaccharomyces pombe mutants undergo partial sporulation during nitrogen starvation
Autophagy-deficient Schizosaccharomyces pombe mutants undergo partial sporulation during nitrogen starvation
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DOI：
10.1099/mic.0.034389-0
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发表时间：
2009-12-01
期刊：
影响因子：
2.8
通讯作者：
Takegawa, Kaoru
中科院分区：
文献类型：
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作者：
Mukaiyama, Hiroyuki;Kajiwara, Shiro;Takegawa, Kaoru
自噬是当生物体感觉到激进的环境变化时触发的，包括营养饥饿。在自噬过程中，细胞质成分，包括细胞器，被包围在自噬体内，并在溶酶体-空泡融合时降解。在这项研究中，我们表明，加工GFP标记的Atg 8可以作为一个标志物的自噬在裂殖酵母裂殖酵母。使用该标记，还发现13个Atg同源物是裂殖酵母中自噬所需的。在芽殖酵母中，自噬缺陷突变体是无菌的，而在分裂酵母中，我们发现高达30%的具有氨基酸营养缺陷的自噬缺陷细胞能够在提供过量所需氨基酸时恢复孢子形成。此外，我们发现，大约15%的自噬缺陷细胞也能够孢子化时，原养型菌株进行氮饥饿，这表明，裂变酵母可以存储足够的细胞内氮，允许部分孢子形成氮限制条件下，虽然大部分的氮源是由自噬。孢子形成过程的监测显示，该过程在atg 1 Delta和atg 12 Delta突变体的各个阶段被非特异性阻断，可能是由于氨基酸短缺。利用这种部分孢子形成能力的裂变酵母，我们寻求证据，存在一个循环系统的氮源在饥饿。
Autophagy is triggered when organisms sense radical environmental changes, including nutritional starvation. During autophagy, cytoplasmic components, including organelles, are enclosed within autophagosomes and are degraded upon lysosome-vacuole fusion. In this study, we show that processing of GFP-tagged Atg8 can serve as a marker for autophagy in the fission yeast Schizosaccharomyces pombe. Using this marker, 13 Atg homologues were also found to be required for autophagy in fission yeast. In budding yeast, autophagy-deficient mutants are known to be sterile, whereas in fission yeast we found that up to 30% of autophagy-defective cells with amino acid auxotrophy were able to recover sporulation when an excess of required amino acids was supplied. Furthermore, we found that approximately 15% of the autophagy-defective cells were also able to sporulate when a prototrophic strain was subjected to nitrogen starvation, which suggested that fission yeast may store sufficient intracellular nitrogen to allow partial sporulation under nitrogen-limiting conditions, although the majority of the nitrogen source is supplied by autophagy. Monitoring of the sporulation process revealed that the process was blocked non-specifically at various stages in the atg1 Delta and atg12 Delta mutants, possibly due to a shortage of amino acids. Taking advantage of this partial sporulation ability of fission yeast, we sought evidence for the existence of a recycling system for nitrogen sources during starvation.