Investigations of the Effects of Subcellular Sugar Levels on Plastid Morphology
Plastid extensions, known as stromules, are an enigmatic feature of all land plants observed to date but the mechanism by which they extend remains unknown. However, a number of conditions that are directly or indirectly related to sugar accumulation such as fungal infection, viral infestation, abiotic stress, and exogenous sucrose treatment result in their induction suggesting that stromule formation might be linked to sugar metabolism. Indeed a positive relationship was found between chloroplast morphology and modifications to the endogenous sugar levels of Arabidopsis thaliana achieved by various means. Since sugar feeds into the starch, fatty acid, and lipid biosynthesis pathways in plastids my study investigated the role of starch and fatty acid biosynthesis pathways in further detail through the imaging of stromules in living plant cells. Changes in plastid morphology were also assessed in mutants with aberrant starch, fatty acid, or lipid synthesis, and following overexpression of proteins associated with sugar transport and the Oxidative Pentose Phosphate Pathway. The insights obtained from my investigations suggest a strong link between fatty acid metabolism and plastid pleomorphy.