|Avtar, Handa - PURDUE UNIVERSITY|
Submitted to: Cell Death in Plants
Publication Type: Other
Publication Acceptance Date: January 7, 2003
Publication Date: April 7, 2003
Citation: Mattoo, A.K., and Handa, A.K. 2004. Ethylene signaling in plant cell death. In: Nooden, L., editor. Plant Cell Death Processes, New York: Academic Press. p. 125-142. Technical Abstract: Hormonal controls singly or in combination are essential for overall control of growth, development and senescence in plants. A number of plant hormones have been implicated in these processes, namely, auxins, cytokinins, gibberellins, abscisic acid, jasmonates, polyamines and ethylene. Their intracellular levels and the sensitivity of a particular cell type or tissue to respond to them individually or in combination together control plant metabolism and function. Among the plant hormones, the one most associated with promotion of senescence and cell death is ethylene. Ethylene is a simple gaseous hydrocarbon with myriad roles in plant life, viz., seed germination, diageotropism, flowering, abscission, senescence, fruit ripening, and pathogenesis. This chapter deals with the role of ethylene in signaling in senescence and cell death. A well-studied PCD model in plants is camptothecin-mediated cell death in tomato cells . Camptothecin, a topo isomerase-I inhibitor and inducer of PCD in animals, causes cell death in tomato suspension in a manner reminiscent of animal apoptosis ¿ chromatin condensation, DNA and nuclear fragmentation. Using inhibitors that inhibit generation of reactive oxygen species (ROS), superoxide (O2-), hydroxy radicals (OH-) and hydrogen peroxide (H2O2), also inhibit camptothecin-mediated cell death. This is quite interesting in light of the studies that showed that oxidative stress induced by cupric ions generates oxygen free radicals, enhanced ethylene production and membrane fragmentation. In the latter system, scavengers of hydroxy radicals inhibited ethylene production as well as senescence-related protein degradation. ROS also appear to be involved with PCD in barley aleurone cells. The cell death lesions in HR are mimicked in plants exposed to toxic levels of ozone (O3) and inhibitors of ethylene biosynthesis or perception prevent their development. O3 is known to induce ethylene biosynthesis, therefore, cell death both in pathogen attack or when plants are exposed to abiotic stresses involves ethylene action.