Shikanai T, Shimizu K, Ueda K, Nishimura Y, Kuroiwa T, Hashimoto T
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, 630-0101 Japan.
Plant Cell Physiol. 2001 Mar;42(3):264-73. doi: 10.1093/pcp/pce031.
ClpP is a proteolytic subunit of the ATP-dependent Clp protease, which is found in chloroplasts in higher plants. Proteolytic subunits are encoded both by the chloroplast gene, clpP, and a nuclear multi gene family. We insertionally disrupted clpP by chloroplast transformation in tobacco. However, complete segregation was impossible, indicating that the chloroplast-encoded clpP gene has an indispensable function for cell survival. In the heteroplasmic clpP disruptant, the leaf surface was rough by clumping, and the lateral leaf expansion was irregularly arrested, which led to an asymmetric, slender leaf shape. Chloroplasts consisted of two populations: chloroplasts that were similar to the wild type, and small chloroplasts that emitted high chl fluorescence. Ultrastructural analysis of chloroplast development suggested that clpP disruption also induced swelling of the thylakoid lumen in the meristem plastids and inhibition of etioplast development in the dark. In mature leaves, thylakoid membranes of the smaller chloroplast population consisted exclusively of large stacks of tightly appressed membranes. These results indicate that chloroplast-encoded ClpP is involved in multiple processes of chloroplast development, including a housekeeping function that is indispensable for cell survival.
ClpP是ATP依赖性Clp蛋白酶的蛋白水解亚基，存在于高等植物的叶绿体中。蛋白水解亚基由叶绿体基因clpP和一个核多基因家族编码。我们通过烟草叶绿体转化插入破坏了clpP。然而，完全分离是不可能的，这表明叶绿体编码的clpP基因对细胞存活具有不可或缺的功能。在异质clpP破坏体中，叶片表面因结块而粗糙，叶片横向扩展不规则受阻，导致叶片形状不对称且细长。叶绿体由两种群体组成：与野生型相似的叶绿体，以及发出高叶绿素荧光的小叶绿体。叶绿体发育的超微结构分析表明，clpP破坏还诱导了分生组织质体中类囊体腔的肿胀以及黑暗中黄化质体发育的抑制。在成熟叶片中，较小叶绿体群体的类囊体膜仅由大量紧密贴合的膜堆叠组成。这些结果表明，叶绿体编码的ClpP参与叶绿体发育的多个过程，包括对细胞存活不可或缺的管家功能。
