Chloroplasts are autonomously replicating organelles which function to harvest light energy into chemical form in plants. They possess their own DNA and replicating machinery. In this renewal project, Dr. Wu will continue studying the control of DNA replication in the chloroplast of the unicellular green alga, Chlamydomonas. In particular, she will focus on the minimal structural requirements for the DNA replication origin, the development of an in vitro replication system for studying the process, and characterization of a novel 18 kDa iron-sulfur containing membrane protein which exhibits very strong binding to the replication origin and which has electron-transport capability. Some experiments are also proposed using chloroplasts isolated from higher plants, to determine if the information obtained from the algal system are directly relevant to higher plant systems. Chloroplast DNA replicates preferentially in the light phase of the growth cycle. The control of DNA replication initiation, and its relationship to other cellular processes, is not well understood. These proposed experiments promise to shed light on this problem, not only for the green alga, Chlamydomonas, but also for higher plants.
