The demise of the marine cyanobacterium, Trichodesmium spp., via an autocatalyzed cell death pathway
The demise of the marine cyanobacterium, Trichodesmium spp., via an autocatalyzed cell death pathway
复制标题
DOI：
10.4319/lo.2004.49.4.0997
复制
发表时间：
2004-07-01
影响因子：
4.5
通讯作者：
Falkowski, PG
中科院分区：
文献类型：
--
作者：
Berman-Frank, I;Bidle, KD;Falkowski, PG
我们提供了实验室实验证据和野外观察，证明了固氮蓝藻Trichodesum spp.中的一种自动催化的程序性细胞死亡(PCD)途径，这种途径在亚热带和热带海洋中形成了大规模的水华。PCD途径是在磷和铁饥饿以及高光和氧化胁迫下被诱导的。透射电子显微镜显示内部成分包括类囊体膜、羧基体膜和气泡的形态降解，而质膜保持完好。生理应激细胞的核酸内切酶活性和末端d-UTP缺口末端标记显着升高。核酸降解与人caspase-3多克隆抗血清的免疫反应性增强和caspase特异性底物DEVD的切割增强是一致的。Caspase活性与死亡率呈正相关，并被不可逆caspase抑制剂Z-VAD-FMK抑制。对红曲霉基因组的搜索发现了几个含有保守的caspase结构域结构的蛋白质序列，包括在真正的caspase、副caspase和metcaspase中发现的含有组氨酸和半胱氨酸的催化二联体。在具有古老进化历史的细菌光自养体内，caspase样酶诱导PCD需要重新评估细胞死亡级联的起源和作用。这一过程是一种以前未被研究过的死亡机制，可能导致自然毛霉水华的终止，并可能影响海洋中有机物的通量。
We present experimental laboratory evidence and field observations of an autocatalyzed, programmed cell death (PCD) pathway in the nitrogen-fixing cyanobacterium Trichodesmium spp., which forms massive blooms in the subtropical and tropical oceans. The PCD pathway was induced in response to phosphorus and iron starvation as well as high irradiance and oxidative stress. Transmission electron microscopy revealed morphological degradation of internal components including thylakoids, carboxysomes, and gas vesicles, whereas the plasma membranes remained intact. Physiologically stressed cells displayed significantly elevated endonuclease activity and terminal d-UTP nick-end labeling. Nucleic acid degradation was concordant with increased immunoreactivity to human caspase-3 polyclonal antisera and enhanced cleavage of a caspase-specific substrate, DEVD. Caspase activity was positively correlated with mortality and was inhibited by the irreversible caspase inhibitor Z-VAD-FMK. A search of the Trichodesmium erythraeum genome identified several protein sequences containing a conserved caspase domain structure, including the histidine- and cysteine-containing catalytic diad found in true caspases, paracaspases, and metacaspases. Induction of PCD by caspase-like proteases in a bacterial photoautotroph with an ancient evolutionary history requires a reassessment about the origins and roles of cell death cascades. This process is a previously unappriciated mortality mechanism that can lead to the termination of natural Trichodesmium blooms and that can influence the fluxes of organic matter in the ocean.