Laboratory of Gene Analysis

Organelles unique to plant cells

Plant cells contain two DNA-containing organelles, plastids and mitochondria, that evolved from endosymbiotic bacteria (respectively, cyanobacteria and a-proteobacteria). During evolution, most of the endosymbiont genes were transferred to the nuclear genome, and extensive genome rearrangement occurred. In modern cells, the biosynthesis and assembly of photosystems and cellular respiration apparatus in organelles are cooperatively controlled by the organelle and nuclear genomes. We are seeking to understand the evolution and function of the plastid and mitochondrial genomes.

Retrograde signaling for organelle biogenesis

Plastids and mitochondria possess their own genetic systems, which have prokaryotic as well as eukaryotic features. Posttranscriptional RNA processing of primary transcripts is an important step in the control of organelle gene expression. RNA processing steps include RNA cleavage/trimming, RNA editing, RNA splicing, and RNA stability. A number of specific protein factors are believed to be involved in these steps. Identification of these regulatory factors, which are mostly encoded by the nuclear genome, is an important area of inquiry. In addition, some signaling from organelles, termed “retrograde signaling”, is thought to modulate expression of nuclear-encoded organelle related genes. Our goal is to understand the regulatory mechanisms that coordinate gene expression between the organelle and nuclear genomes by retrograde signaling.

RNA editing in plant organelles

RNA editing is an enigmatic phenomenon in which specific cytidines (C) in the transcripts are changed to uridines (U); it occurs in many transcripts of plant organelles. For example, in flowering plants, over 500 editing sites have been identified in the mitochondria and plastids. However, little is known about the molecular mechanisms of the organelle RNA editing process. Our ongoing work concerns RNA editing. Many questions remain unanswered about the mechanism and evolution of this unique C-to-U RNA editing. Our recent studies have revealed that nuclear-encoded pentatricopeptide repeat (PPR) proteins are site-specific RNA editing factors. This will help elaborate our understanding of plant organelle RNA editing.

Lab members