Which of the following is NOT one of the reasons why Arabidopsis has been an excellent model system for plants? 1.It is easy to grow and doesn’t take up much space. 2.It has a small genome that is completely sequenced, and has a complete genetic map. 3.It tastes good and is valued by the farm industry. 4.It self-pollinates but can also be out-crossed by hand for genetic crosses. 5.It has a short life cycle of ~6 weeks.

Which plant is showing an etiolated phenotype? 1.Plant 1 2.Plant 2 3.Plant

Which seedling was germinated in the presence of the plant hormone ethylene in the dark? 1.Seedling 1 2.Seedling 2 1 2

What is the ethylene-response phenotype in dark-grown seedlings called? 1.Phototropism 2.Radicle 3.Hypocotyl tropism 4.Thigmomorphogenesis 5.The triple response

Which of these seedlings is insensitive to the plant hormone ethylene? 1.Seedling 1 2.Seedling 2 3.Seedling No ethylene + ethylene

How do research labs screen for mutants that are insensitive to ethylene? Mutagenized seeds are plated on growth media that: 1.contains abscisic acid and is incubated in the dark 2.contains ACC and is incubated under lights in the growth chamber 3.contains ACC and is incubated in the dark 4.is incubated in the dark

Which seedling is a “constitutive ethylene- response” mutant? 1.Seedling 1 2.Seedling 2 3.Seedling 3 4.Seedling No ethylene + ethylene

How do research labs screen for mutants that have a constitutive response to ethylene? Mutagenized seeds are plated on growth media that: 1.contains abscisic acid and is incubated in the dark 2.contains ACC and is incubated under lights in the growth chamber 3.contains ACC and is incubated in the dark 4.is incubated upside down in the dark

What kind of mutant is the abi1-1 mutant? Wild typeabi1-1 Dormancy (No germination) ABA NO Dormancy (Germination) NO ABA NO Dormancy (Germination) NO ABA ABA NO Dormancy (Germination) 1.ABA insensitive 3. Constitutive ABA response 2. Seed germination 4. Viviparous mutant

The Arabidopsis abi1-1 mutant is ABA-insensitive From Koornneef, M., Reuling, G., and Karssen, C.M. (1984). The isolation and characterization of abscisic acid-insensitive mutants of Arabidopsis thaliana. Physiologia Plantarum 61: , with permission from John Wiley and Sons Wild typeabi1-1 Dormancy (No germination) ABA NO Dormancy (Germination) NO ABA NO Dormancy (Germination) NO ABA ABA NO Dormancy (Germination)

abi1-1 mutants are ABA-insensitive in all their responses Leung, J., Bouvier-Durand, M., Morris, P., Guerrier, D., Chefdor, F., and Giraudat, J. (1994). Arabidopsis ABA response gene ABI1: features of a calcium-modulated protein phosphatase. Science 264: ; Meyer, K., Leube, M., and Grill, E. (1994). A protein phosphatase 2C involved in ABA signal transduction in Arabidopsis thaliana. Science 264: Root growth is not inhibited on ABA Guard cells are not ABA- responsive Wild type abi1 Germination is not inhibited on ABA

Ethylene responses in Arabidopsis “Triple Response” Inhibition of leaf cell expansion Senescence Ethylene-induced gene expression

Based on the variety of topics in this workshop, can you think of an idea for a mutant screen in plants? How would you carry out your screen?

Wild typeabi1-1 Dormancy (No germination) ABA NO Dormancy (Germination) NO ABA NO Dormancy (Germination) NO ABA ABA NO Dormancy (Germination) Can you make a similar table for your predicted ethylene mutants?

+ ACC No ACC Wild typeMutant Ethylene insensitive mutants (“ein”) *

+ ACC No ACC Wild typeMutant Constitutive ethylene response mutants (“ctr”) *