The bacterial stringent response, conserved in chloroplasts, controls plant fertilization
The bacterial stringent response, conserved in chloroplasts, controls plant fertilization
复制标题
DOI：
10.1093/pcp/pcm177
复制
发表时间：
2008-02-01
影响因子：
4.9
通讯作者：
Takamiya, Ken-ichiro
中科院分区：
文献类型：
--
作者：
Masuda, Shinji;Mizusawa, Kazuki;Takamiya, Ken-ichiro
叶绿体是植物的重要细胞器，为寄主细胞执行各种各样的代谢过程，包括光合作用以及氨基酸和脂肪酸的生物合成。细胞器在功能上保留了许多细菌系统，暗示其起源于光合细菌的共生。在细菌细胞中，这种严格的反应是由一个小核苷酸5‘-二磷酸鸟苷3’-二磷酸(PpGpp)介导的基因表达的全球调控系统，这是细胞适应各种环境刺激(如氨基酸饥饿)所必需的。最近的研究表明，与细菌ppGpp合成酶/水解酶类似的蛋白质在植物中是保守的，尽管它们的确切作用尚不清楚。在这里，我们证明了叶绿体的严格反应对于正常的植物受精是至关重要的。具体地说，拟南芥ppGpp合成酶同源物CRSH(钙激活的RelA/Spot Homolog)在体外表现出钙依赖的ppGpp合成活性，并在体内定位于叶绿体。在拟南芥中，CRSH基因的敲除突变导致角果大小和种子产量显著减少，表明植物的生殖是通过ppGpp介导的严格反应受叶绿体功能控制的。
The chloroplast, an essential organelle for plants, performs a wide variety of metabolic processes for host cells, which include photosynthesis as well as amino acid and fatty acid biosynthesis. The organelle conserves many bacterial systems in its functions, implicating its origin from symbiosis of a photosynthetic bacterium. In bacterial cells, the stringent response acts as a global regulatory system for gene expression mediated by a small nucleotide, guanosine 5'-diphosphate 3'-diphosphate (ppGpp), that is necessary for cell adaptation to diverse environmental stimuli such as amino acid starvation. Recent studies indicated that proteins similar to the bacterial ppGpp synthase/hydrolyase are conserved in plants, although their precise roles are not known. Here we show that the stringent response in chloroplasts is crucial for normal plant fertilization. Specifically, one of the Arabidopsis ppGpp synthase homologs, CRSH (Ca2+-activated RelA/SpoT homolog), exhibits calcium-dependent ppGpp synthesis activity in vitro, and is localized in chloroplasts in vivo. A knockdown mutation of CRSH in Arabidopsis results in a significant reduction in silique size and seed production, indicating that plant reproduction is under the control of chloroplast function through a ppGpp-mediated stringent response.