Leaf Senescence and Ethylene Signaling

Leaf senescence, one of the developmental phases of the leaf, is a genetically programmed and highly regulated degenerative process controlled by developmental and environmental signals. It is characterized by different physiological, biochemical and molecular changes including the degradation of chlorophyll, proteins, lipids and nucleic acids. Leaf senescence is regulated both by environmental and internal factors. One of the important endogenous factors determining leaf senescence is phytohormones. Ethylene is one of the essential phytohormones that promote leaf senescence. Although the discovery of the role of ethylene in senescence dates back to almost a century, the molecular mechanisms underlying ethylene-regulated leaf senescence have been elucidated more recently primarily through genetic and molecular studies. In this chapter, we summarize the current understanding of ethylene signaling, with a primary focus on the perception and transduction of leaf senescence signals along with the different transcriptional factors and the downstream regulatory mechanisms of the signaling pathway.