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

Which of the following is NOT one of the reasons why Arabidopsis has been an excellent model system for plants? It is easy to grow and doesn’t take up much space. It has a small genome that is completely sequenced, and has a complete genetic map.

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

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

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

  3. 1 2 • Which seedling was germinated in the presence of the plant hormone ethylene in the dark? • Seedling 1 • Seedling 2

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

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

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

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

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

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

  10. The Arabidopsis abi1-1 mutant is ABA-insensitive Wild type abi1-1 ABA ABA NO Dormancy (Germination) Dormancy (No germination) NO ABA NO ABA NO Dormancy (Germination) NO Dormancy (Germination) 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: 377-383, with permission from John Wiley and Sons.

  11. abi1-1 mutants are ABA-insensitive in all their responses Germination is not inhibited on ABA Root growth is not inhibited on ABA Guard cells are not ABA-responsive Wild type abi1 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: 1448-1452; Meyer, K., Leube, M., and Grill, E. (1994). A protein phosphatase 2C involved in ABA signal transduction in Arabidopsis thaliana. Science 264:1452-1455.

  12. Inhibition of leaf cell expansion Ethylene responses in Arabidopsis Ethylene-induced gene expression “TripleResponse” Senescence

  13. 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?

  14. Can you make a similar table for your predicted ethylene mutants? Wild type abi1-1 ABA ABA NO Dormancy (Germination) Dormancy (No germination) NO ABA NO ABA NO Dormancy (Germination) NO Dormancy (Germination)

  15. Wild type Mutant +ACC No ACC Ethylene insensitive mutants (“ein”) *

  16. Wild type Mutant +ACC No ACC Constitutive ethylene response mutants (“ctr”) *

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