Subcellular Responses of Plant Cells to Phosphate Starvation and Exogenous Sucrose Supply
Michael Wozny, University of Guelph, 2015. Advisor: Dr. Jaideep Mathur. Stromules are thin tubules of the plastid envelope, filled with stroma. The function of these enigmatic structures is unclear, as is the mechanism of their formation. Stromules are known to closely align with and be shaped by the rearrangement of the endoplasmic reticulum. As such, the pulling force caused by the movement of plastids and other organelles connected by membrane contact sites has been proposed as a means of initiating stromule formation. This study reports that stromule frequency is affected by phosphate starvation in a sucrose dependent manner. Replacement of extraplastidic phospholipids with plastid synthesized galactolipids is a well characterized phosphate starvation response which is also responsive to sucrose availability. Transcripts of phosphate starvation induced galactolipid synthase genes were found in greater abundance following sucrose treatment of plants which also increase stromule frequency. Phosphate starvation induced lipid remodeling and trafficking is thought to be concentrated at membrane contact sites between the plastid and other organelles. Conclusions drawn from this investigation as well as other reports of increased stromule frequency suggest that increased galactolipid synthesis and trafficking between plastids and other organelles is a causative factor influencing stromule frequency.