The role of aquaporins in the aluminum tolerance of Oryza sativa

Project Summary

In acidic soils with pH lower than 5.5, aluminum (Al) solubilizes to the highly rhizotoxic species Al³⁺, which poses a threat to crop production worldwide. The Al³⁺ ion targets the root apex and inhibits root growth, thus decreasing plant biomass.  While many crop species prevent this damage through exclusion mechanisms involving organic acid exudation, many Al hyperaccumulators safely sequester Al³⁺ internally into subcellular compartments such as vacuoles.  One such hyperaccumulator,Hydrangea macrophylla, transports soil Al³⁺ into the petal cell vacuoles with aquaporin Al transporters localized in the plasma and vacuolar membranes. Two aquaporin genes in Oryza sativa, AQP5 andAQP6, have been found to be upregulated in the presence of aluminum. To identify the subcellular localization of these aquaporins and to characterize their roles in rice Al tolerance, AQP5 and AQP6fused to green fluorescent protein were transiently co-expressed with membrane-specific red fluorescent protein markers in tobacco leaves through agrobacterium-mediated co-infiltration. Their expression patterns were observed using a confocal microscope.  Both aquaporins showed localization in the endoplasmic reticulum and plasma membrane, which may indicate protein trafficking between the two membranes. The function of the aquaporins was characterized by growing yeast transformed with either AQP5 or AQP6 in low pH, low Mg (LPM) liquid media with differing Al³⁺ concentrations; growth measurements from these cultures suggest AQP5 and AQP6 may improve aluminum tolerance. Future directions include verification of plasma membrane localization with DAPI staining and transgenic expression to determine a phenotype in O. sativa.

My Experience

I greatly enjoyed my summer internship at BTI. In the Kochian lab, I not only learned new and useful research techniques but I also discovered more about the research process. I was able to work in a highly diverse lab with many international collaborators.  My mentor was very helpful, and allowed me to be increasingly independent in my lab work. Even though my project focused on molecular biology, I was also exposed to plant breeding and physiology. Now, I have clarified my interests as a scientist and feel confident about my decision to apply to graduate programs this fall.