Programmed cell death in plant development

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. 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 PCD in plants. Lace plant is an aquatic plant native to Madagascar and difficult to grow in aquarium conditions. I have successfully developed an axenically cultured lace plant system to work on developmental PCD in plants. We still do not know what cues trigger PCD at the appropriate stage of leaf development, the signaling pathways and the molecular mechanism(s). Therefore, my overall aim is to identify factors inducing perforations and the mechanisms that regulate the PCD in lace plant using microscopical, biochemical, and molecular techniques with five approaches. 1) To understand the interconnection between ethylene and caspase-like proteases in PCD. 2) To test the effect of inhibitors of calcium on cell death in plants. 3) To use molecular markers to characterize key events of PCD in live cells. 4) To compare induced and developmental PCD in the same plant species. 5) To identify genes involved in PCD in lace plant perforation formation. These results will help us to determine whether there are common mechanisms between animal and plant PCD or whether they evolved independently. Identification of PCD genes has the potential to be useful in agricultural applications such as inhibition or delaying leaf, flower and fruit senescence.