Lab Research

key words: molecular biology, plant gene expression, mRNA stability, translation, chloroplasts, and Chlamydomonas.

My research interests are in molecular biology and plant gene expression. In particular, I study mRNA stability, translation, and the mechanisms that control these events in plant cells. Currently, my lab is investigating the petD gene in the single celled alga Chlamydomonas reinhardtii. petD is located in the 197-kb chloroplast genome and it encodes subunit IV (SUIV) of the cytochrome b6/f complex, which is essential for photosynthesis. Expression of the petD gene is dependent on nucleus-encoded regulatory proteins which are thought to interact with petD mRNA to stabilize the transcript and activate translation.

Our lab is using molecular biology and genetic techniques to further study the mechanisms that control petD mRNA stability and translation. As a Postdoctorate in Dr. David Stern's Lab at the Boyce Thompson Institute for Plant Research (Cornell University) I was involved in characterizing three cis-acting regulatory sequences (elements) in this mRNA (Fig. 1). These elements are essential for RNA stability and translation, and likely function as binding sites for gene-specific regulatory proteins. We are studying the sequences and RNA secondary structures (Fig. 2 and Fig. 3) of these elements with the goal of understanding how regulatory proteins recognize and bind specific chloroplast mRNAs to promote RNA stability and/or translation.

Fig. 1. Gene diagram of petD and the three characterized cis-acting regulatory elements in the 5' untranslated region (UTR) of petD mRNA. The position (nt number) and function of the regulatory elements are indicated. (Back to Top)

Fig. 2. Element I is located at the 5' end of petD mRNA. The combination of primary sequence and secondary structure is believed to provide specificity for the binding of the MCD1 regulatory protein, which promotes RNA stability and translation. This energy-minimized structure was predicted by mfold, and is consistent with in vitro and in vivo experemental data. The line indicates element I nucleotides critical for RNA stability and translation. (Back to Top)

Fig. 3. Element III is located at position 317-330 (just upstream of the translation start site). The sequence and secondary structures are believed to provide specificity for binding of regulatory proteins which promote translation. This energy-minimized structure was predicted by mfold, and is consistent with in vitro and in vivo experemental data. The line indicates element III nucleotides critical for translation. The AUG translation start site is also highlighted. (Back to Top)

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Questions, comments or suggestions should be e-mailed to David Higgs (higgs@uwp.edu)