Dr. Orit Shaul

The research in our lab has two main focuses. The first is magnesium transport in plants, a subject about which relatively little is known. We cloned and characterized the Arabidopsis thaliana MHX transporter (AtMHX), which is the first exchanger of protons (H⁺) with magnesium (Mg²⁺) ions that had been cloned from any organism. This transporter is localized in the vacuolar membrane and can carry Mg²⁺ and Zn²⁺ ions into the plant vacuole. The vacuole is a key organelle in the maintenance of metal and proton homeostasis in plants. We investigate the function, phylogenetics, and regulation of expression of plant MHX transporters.

While we studied the regulation of AtMHX expression, we realized that it is controlled by several mechanisms about which relatively little is known, including intron-mediated enhancement (IME) and nonsense-mediated mRNA decay (NMD). This led us to the second main focus of the lab, which is regulation of gene expression in plants, with particular focus on IME and NMD. The regulatory elements of AtMHX are used as a model system in some of these studies. IME is the ability of introns to increase gene expression. An interesting finding of the lab was the identification, within the 5' UTR intron of AtMHX, of the first intronic element that boosts translation. NMD is a post-transcriptional mechanism that controls the stability of aberrant and normal mRNAs, and has a great impact on AtMHX expression. We are interested in how NMD is regulated, a subject which is currently not well understood. We identified an NMD feedback-loop that controls the expression of the NMD factor UPF3, and demonstrated the physiological significance of this feedback loop.