Investigating Organelle Responses and Interactions in Plants

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A multicellular organism's survival following stress relies on its ability to quickly re-establish and maintain homeostasis in its cells. Since uncontrolled human activity is profoundly altering our environment at a rapid pace it is imperative that we explore and learn about stress alleviation mechanisms in different organisms. Considering their success in surviving and continuing to proliferate in diverse habitats despite numerous abiotic and biotic stresses I have chosen to work with plants. Thus, my long--term research program aims at understanding homeostasis mechanisms in plant cells. Earlier NSERC-funded projects to my lab have resulted in new insights on the rapid sub-cellular responses in plants, including the formation of transient organelle extensions, within seconds of sensing a change in the environment. These findings and the tools generated so far provide a firm basis for the present proposal. Here, acknowledging the plastids as subcellular interaction hubs I focus on understanding their behaviour and interactions with other organelles. Four complementary areas of investigation are proposed. 1. Investigating the role of acyl-lipids on rapid changes in plastid morphology and behaviour: Plastids form the major site of de novo fatty acid synthesis in plants but the cell biological mechanisms involved in acyl-lipid dispersal to the rest of the cell are not understood. I propose to investigate the role of acyl-lipid traffic through the plastid envelope membranes to achieve insights on the phenomenon. 2. Elucidating the role of plastid pleomorphy and acyl/lipid metabolism in response to abiotic stress: It is well known that plant response to stress induces changes in its acyl-lipid profile. So far this finding is not associated with alterations in plastid morphology and behaviour.Using plastid--targeted fluorescent probes I will investigate whether changes in acyl-lipid and plastid morphology in response to stress can provide new insights on stress amelioration measures in plants. 3. Investigating the role of plastid--ER membrane contact sites (MCS) as conduits for lipid trafficking: This new area of investigation will provide insights on MCS formation between plastids and the ER for facilitating bidirectional acyl-lipid traffic. 4. Understanding the general role of organelle extensions in cellular homeostasis: Living plant cells exhibit tubular extensions sporadically from several organelles, including plastids but their significance is not known. Using several double and triple transgenics and extending the investigation to lipid droplets I propose to investigate the role of organelle extensions in maintaining homeostasis. The proposal relies heavily on live--cell imaging, biochemistry and lipidomics. Besides creating considerable opportunities for HQP training in molecular and cellular biology techniques, providing valuable insights on the living plant cell it will lead to high quality research publications and public education.