Getting the green light: How chloroplast gene expression is activated by light


In plants, photosynthesis occurs within chloroplasts, organelles that contain a genome encoding photosynthetic complexes. Growth and survival of plants depends on regulated expression of these chloroplast genes in response to developmental and environmental cues. For example, exposure to light causes a dramatic increase in the transcription of photosynthetic genes. This is a defining stage of plant development, but, despite its importance, we do not know how it occurs at the molecular level.

In this project, we will investigate how chloroplast transcription is turned on and allow plants to become green. This exciting project will employ a variety of cutting-edge methods to characterise the structures, functions and biological roles of proteins that activate gene expression.

Cryogenic electron microscopy (cryo-EM) will be employed to visualise the structure of gene expression complexes. Complementary biochemical and biophysical experiments will be performed to understand the relationship to their biochemical activities. Finally, the essential roles of these proteins in plants will be tested by examining the effect of targeted mutations on chloroplast maturation.

These discoveries will support the long-term effort to better control photosynthetic output and timing for improved crops and biotechnologies. They will also shed new light on fundamental biological questions of how genes are read.

The student will be trained in diverse and transferrable scientific skills: cryo-EM, protein purification, quantitative biochemical and biophysical methods, general molecular biology techniques and plant mutational analysis.

Special attention will be given to training in cryo-EM, which represents an increasingly powerful method of visualising large and dynamic molecular machines.
The JIC hosts a wealth of expertise in plant biology, gene expression mechanisms, and structural biology, and is therefore an excellent research environment for this project.


Webster MW and Weixlbaumer A (2021) Macromolecular assemblies supporting transcription-translation coupling. Transcription 12:103-125. PMID: 34570660. DOI: 10.1080/21541264.2021.1981713.

Webster MW, Takacs M, Zhu C, Vidmar V, Eduljee A, Abdelkareem M, Weixlbaumer A (2020) Structural basis of transcription-translation coupling and collision in bacteria. Science 369:1355-59. PMID: 32820062. DOI: 10.1126/science.abb5036.

Webster MW, Stowell JAW, Passmore LA (2019) RNA-binding proteins distinguish between similar sequence motifs to promote targeted deadenylation by Ccr4-Not. eLife 8:e40670. PMID: 30601114. DOI: 10.7554/eLife.40670.

Webster MW, Chen YH, Stowell JAW, Alhusaini N, Graveley B, Coller J, Passmore LA (2018) mRNA deadenylation is coupled to translation rates by the differential activities of Ccr4-Not nucleases. Molecular Cell, 70(6): 1089-1100. PMID: 29932902. DOI: 10.1016/j.molcel.2018.05.033.

Webster MW, Stowell JAW, Tang TTL, Passmore LA (2017) Analysis of mRNA deadenylation by multi-protein complexes. Methods, 126:95-104. PMID: 28624538. DOI: 10.1016/j.ymeth.2017.06.009.