Programmed cell death in plant development

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Programmed cell death (PCD) is a genetically-enabled process in which select cells organize their own destruction. PCD is ubiquitous in all eukaryotic kingdoms and is employed by both unicellular and multicellular organisms as part of normal development or in response to external stimuli. In plants, PCD is necessary for growth and survival and can either be developmentally regulated or environmentally induced. A unique example of developmental PCD is perforation (holes) formation in lace plant leaves. These holes are situated equidistantly between longitudinal and transverse veins, giving leaves a lattice-like pattern. During perforation formation, discrete subpopulations of cells undergo PCD while adjacent cells remain intact. Lace plant is native to Madagascar and difficult to grow in aquarium conditions. I have successfully developed a tissue culture system to work on developmental PCD in lace plant. We still do not know what cues trigger PCD at a specific stage of leaf development, as far as the signaling pathways and the molecular mechanisms are concerned. I have characterized the cell death process during perforation formation in lace plant and showed that this aquatic plant is an ideal model system to study developmental PCD in vivo. Therefore, the long term objective of my research is to achieve a fundamental understanding of the mechanisms involved in developmental PCD using lace plant leaf morphogenesis as a model system. This will be achieved through the following objectives: 1) Characterize the order of PCD events using live cell imaging techniques and generate 3-D models; 2) Investigate changes in the actin cytoskeleton during lace plant PCD; 3) Investigate the roles of calcium and mitochondrial inner membrane space proteins in the initial stages of PCD; 4) Evaluate the role of ethylene as an induction signal in lace plant PCD; 5) Identify ethylene receptor genes using degenerate primers. These results will help us to determine whether there are common mechanisms between animal and plant PCD or whether they evolved independently.