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Research Interests

Our laboratory studies how chloroplasts -- the organelles that perform photosynthesis in plants -- are assembled and regulated. Chloroplasts harbor a small genome, a legacy of their cyanobacterial ancestry.  Our research is directed at understanding how the genetic machineries in the chloroplast and nucleus collaborate to produce a photosynthetically competent chloroplast that responds dynamically to environmental and developmental cues. In particular, we study how nuclear genes influence the synthesis of chloroplast-encoded proteins, with a focus on the post-transcriptional control of chloroplast gene expression. Our research combines genetic and biochemical approaches to identify relevant genes, define their functions, and elucidate the underlying mechanisms. 

mRNA metabolism is far more complex and translational control is much more prevalent in chloroplasts than in their bacterial ancestor. Our work has elucidated mechanisms underlying this complexity, including the discovery of novel families of nucleus-encoded RNA binding proteins that mediate these processes and that coevolved with them. We focused on a prime example, the pentatricopeptide repeat (PPR) proteins, revealing how they recognize specific RNA sequences via an amino acid "code" to promote the stabilization and translation of specific chloroplast mRNAs.  We have harnessed these discoveries to develop novel tools for basic research and biotechnology. 

Our current research centers on a striking example of translational control: the light-regulated translation of the chloroplast psbA mRNA.  psbA encodes the D1 protein of photosystem II (PSII), which is damaged by light and must be continually replaced with newly synthesized D1 to maintain photosynthesis. Our work has revealed an exquisitely responsive translational rheostat that matches D1 synthesis to the real-time need for PSII repair via a mechanism coupled to the assembly status of D1 itself.