Student: Nicola Harrison-Lowe
Mentor: Laura Olsen
Department of Molecular, Cellular and Developmental Biology

Nicola Harrison-Lowe is one of a number of students whose research focuses on plant biology using the model organism Arabidopsis Thaliana. Her project focuses on autophagy, which is a conserved intracellular recycling pathway that assists cell survival under hostile conditions. Induced under low-glucose regimes, autophagy proceeds with the sequestration of cytoplasmic components into vesicles and subsequent trafficking to the vacuole for degradation. Although well studied in yeast and mammalian systems, little is known about this pathway in plants. Bioinformatic analysis has identified sequence-based homologues to 18 known autophagy proteins in Arabidopsis. Of these, AtATG6 is a homologue of mammalian Beclin 1 and the yeast gene ATG6/VPS30. This protein is most interesting due its possible conserved association with a phosphoinositol-3-kinase (PI3K) complex, which is essential for vesicle formation and may be involved in PI3P-mediated signaling. In addition, Beclin1 is deleted in the majority of breast cancer cells and a mouse null mutation is embryonic lethal. Harrison-Lowe's studies indicate that ATG6 homozygous mutants are not viable (soil grown) and that heterozygotes suffer reduced viability under stress conditions. In addition, RT-PCR analysis shows that two isoforms of AtATG6 are expressed in Arabidopsis. She is currently investigating the temporal and spatial expression of the two ATG6 isoforms to elucidate any differences. Yeast two-hybrid analysis has been used to identify several putative ATG6 protein-interaction partners consistent with involvement of a PI3K. She is in the process of confirming these using co-immunoprecipitation techniques. Additional work is underway to develop an in vivo autophagy assay using plant protoplasts and to construct reporter plant lines for further molecular characterization and protein localization/overexpression studies.