Our research is focused on the biogenesis and regulation of chloroplasts (plastids) in plants, particularly in relation to protein import and degradation.
Chloroplast Protein Import
Plastids are a diverse family of plant organelles with numerous functions vital for plant growth. They include chloroplasts and a range of non-photosynthetic variants. Most plastid proteins are nucleus-encoded and synthesised in the cytosol as precursors with N-terminal targeting peptides. Import of these precursors into chloroplasts is mediated by the TOC-TIC translocons. We seek to understand these import systems mechanistically, as well as their proteolytic regulation via CHLORAD (chloroplast-associated protein degradation). To do this we apply a full spectrum of molecular, genetic, cellular, and biochemical approaches, and we study the model plant Arabidopsis thaliana as well as a range of crop species.
Control By Ubiquitination
Our work revealed that plastids are directly regulated by the ubiquitin-proteasome system. We discovered a ubiquitin E3 ligase in the plastid outer membrane called SP1 which targets the TOC machinery. Later, we showed that SP1 is part of a broader system termed CHLORAD, which extracts and delivers plastid proteins to the cytosolic proteasome for degradation. By regulating the protein import machinery, CHLORAD controls the plastid’s proteome, functions, and developmental fate. Many mechanistic details of the pathway remain unclear, and addressing these knowledge gaps is a major focus of our research. We are also exploring novel crop improvement strategies and other diverse agricultural applications including plant stress responses.