Miyagishima Shin-ya, Froehlich John E, Osteryoung Katherine W
Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Plant Cell. 2006 Oct;18(10):2517-30. doi: 10.1105/tpc.106.045484. Epub 2006 Sep 22.
During plastid division, the dynamin-related protein ACCUMULATION AND REPLICATION OF CHLOROPLASTS5 (ARC5) is recruited from the cytosol to the surface of the outer chloroplast envelope membrane. In Arabidopsis thaliana arc5 mutants, chloroplasts arrest during division site constriction. Analysis of mutants similar to arc5 along with map-based cloning identified PLASTID DIVISION1 (PDV1), an integral outer envelope membrane protein, and its homolog PDV2 as components of the plastid division machinery. Similar to ARC5, PDV1 localized to a discontinuous ring at the division site in wild-type plants. The midplastid PDV1 ring formed in arc5 mutants and the ARC5 ring formed in pdv1 and pdv2 mutants, but not in pdv1 pdv2. Stromal FtsZ ring assembly occurred in pdv1, pdv2, and pdv1 pdv2, as it does in arc5. Topological analysis showed that the large N-terminal region of PDV1 upstream of the transmembrane helix bearing a putative coiled-coil domain is exposed to the cytosol. Mutation of the conserved PDV1 C-terminal Gly residue did not block PDV1 insertion into the outer envelope membrane but did abolish its localization to the division site. Our results indicate that plastid division involves the stepwise localization of FtsZ, PDV1, and ARC5 at the division site and that PDV1 and PDV2 together mediate the recruitment of ARC5 to the midplastid constriction at a late stage of division.
在质体分裂过程中，动力蛋白相关蛋白叶绿体5积累与复制（ARC5）从细胞质被招募到叶绿体被膜外膜表面。在拟南芥arc5突变体中，叶绿体在分裂位点缢缩时停滞。对与arc5相似的突变体进行分析并结合图位克隆，确定了质体分裂1（PDV1），一种外被膜整合蛋白，及其同源物PDV2是质体分裂机制的组成部分。与ARC5相似，PDV1在野生型植物的分裂位点定位于一个不连续的环。arc5突变体中形成了质体中部的PDV1环，pdv1和pdv2突变体中形成了ARC5环，但在pdv1 pdv2双突变体中未形成。基质中的FtsZ环组装在pdv1、pdv2和pdv1 pdv2中发生，就像在arc5中一样。拓扑分析表明，PDV1跨膜螺旋上游带有假定卷曲螺旋结构域的大的N端区域暴露于细胞质中。保守的PDV1 C端甘氨酸残基的突变并未阻止PDV1插入外被膜，但确实消除了其在分裂位点的定位。我们的结果表明，质体分裂涉及FtsZ、PDV1和ARC5在分裂位点的逐步定位，并且PDV1和PDV2共同在分裂后期介导ARC5被招募到质体中部缢缩处。
