The plant hormone ethylene What does ethylene do? Is ethylene important? How can we study ethylene and use that knowledge to benefit humans? Ethylene is a GAS!!! What’s a hormone?

Plants synthesize ethylene in response to stress Wounding Flooding Drought stress Biotic stress Heat stress Cold stress Osmotic stress Mechanical stress UV stress Pathogen attack Ethylene has it’s hands in everything

ETHYLENE is also a pollutant in the environment

Ethylene responses Developmental processes Fruit ripening - ethylene is essential Promotion of seed germination Root initiation Bud dormancy release Inhibition/promotion of flowering Sex shifts in flowers Senescence of leaves, flowers Responses to abiotic and biotic stress Abscission of leaves, flowers, fruits Epinasty of leaves Inhibition/promotion of cell division/elongation Altered geotropism in roots, stems Induction of phytoalexins/disease resistance Aerenchyma formation

Historical background Ethylene has been used (unwittingly) throughout history Wood burning fires promote synchronous flowering in pineapple Gashing promotes ripening in figs (4 days later)

Historical background 1800s Illuminating gas caused detrimental effects Plants around the beltway

Wounding induces ethylene production Ethylene causes senescence Can block ethylene response using silver thiosulfate

Apple slices inducing ripening of persimmons 8 days in bag with apple slices Controls, 8 days outside of bag

Ethylene has far-reaching consequences for agriculture and horticulture Transport and storage of fruits and vegetables requires ethylene control Flood-tolerant rice created by expression of ethylene response factor genes “One bad apple spoils the whole bunch…” Therefore, we would like to manipulate the biosynthesis and/or responses to ethylene

Removal of external ethylene

Ethylene hormone signaling What is “signaling”? How is signaling studied? How to get the genes that nature did not already manipulate so that we can manipulate them?

Signal transduction Response Signal plant cell ?

Plant growth, development, and survival depend on appropriate responses to a diverse array of constantly fluctuating external and internal signals

Example of signaling pathway activated by an extracellular signal Signal transduction - the process by which a cell converts one kind of signal or stimulus into another. Signal transduction processes typically involve a sequence of biochemical reactions or other responses within the cell, resulting in a signal transduction pathway