Topic: Assembly of the photosynthetic apparatus: genetic, biochemical and systems approaches

Speaker: Prof. Ralph Bock

Time: 10:00-11:30 AM, 11 Nov., 2025

Venue: Lecture hall 111, Lynn Library

Brief introduction of the speaker:

Dr. Ralph Bock is the Director of the Max Planck Institute of Molecular Plant Physiology in Germany and Honorary Professor at the University of Potsdam. He is a member of the German National Academy of Sciences (Leopoldina), a permanent member of the European Molecular Biology Organization (EMBO), a Foreign Member of the U.S. National Academy of Sciences, and has been consistently recognized as a Highly Cited Researcher globally. As an internationally acclaimed plant molecular biologist, Ralph is a pioneer and leader in organelle biology and plant synthetic biology. He was the first to experimentally demonstrate the horizontal transfer of chloroplast genes to the nuclear genome, revealing the mechanisms of inter-genomic communication between organelles and the nucleus. He has significantly advanced organelle genome engineering technologies and established plant chloroplasts as versatile platforms for synthetic biology, making foundational contributions to plant metabolic engineering and the development of “molecular farming”. His research has also provided comprehensive insights into the regulation of organelle gene expression, RNA processing, and protein assembly. Through synthetic experimental evolution, he has reconstructed key processes underlying speciation. To date, he has published over 250 SCI-indexed research papers, the majority as corresponding author, in top-tier journals including Nature, Science, PNAS, and Nature Communications, with more than 25,000 total citations and an H-index of 80. His honors include an ERC Advanced Grant and the ASPB Martin Gibbs Medal. e serves as a Senior Editor of The Plant Cell and as associate editor or editorial board member for Plant Biotechnology Journal, Molecular Plant, and other journals. Over the years, he has mentored many outstanding scientists who now lead independent research groups across Europe, North America, and Asia.

Abstract:

The photosystems in the thylakoid membrane of chloroplasts belong to the largest and most complex macromolecular assemblies in nature. They are composed of subunits encoded in the chloroplast genome and subunits encoded in the nuclear genome. In addition, they contain hundreds of co-factors, such as chlorophylls, carotenoids and iron-sulfur clusters. The complex architecture of the photosystems requires a highly ordered and (spatially as well as timely) tightly coordinated assembly process to ensure proper subunit incorporation and co-factor attachment.

Using the biogenesis of photosystem I (PSI) as a model process of thylakoid protein complex assembly, we have begun to dissect the assembly process and identify components of the molecular machinery that assembles PSI from its individual subunits. In my talk, I will describe a number of approaches that my laboratory has developed to identify and characterize assembly factors participating in the biogenesis of PSI. These include (i) systematic reverse genetics studies in the nuclear and chloroplast genomes, (ii) protein-protein interaction screens, (iii) co-expression analyses, and (iv) the biochemical isolation of intermediate complexes in the PSI assembly process. Our data suggest that a large number of protein factors is specifically involved in the biogenesis of PSI in the thylakoid membrane of chloroplasts, and multiple PSI assembly factors cooperate to mediate the proper insertion of each PSI subunit into the nascent complex.