PMS L3

Question 1

Give 4 examples of ancient crop domestication

Answer 1

• Watermelon: Originally used as water carriers, with selection for sweetness and colour.
• Bananas: Domesticated in Papua New Guinea; evolved from diploid, seeded varieties to modern triploid,
  seedless forms.
• Eggplant: Domesticated in Asia, leading to changes in size, colour, and alkaloid content.
• Carrots: Domesticated in Central Asia; the orange variety became prevalent in the 15th-16th centuries in
  Europe.

Question 2

Give an example of how selective breeding on a single species can produce different crops through crop plasticity.

Answer 2

• Broccoli, cauliower, cabbage, and kohlrabi are all derived from Brassica oleracea (Wild Mustard)
• Selectively bred to exaggerate different features.

Question 3

Give an example of convergent phenotypic changes during domestication.

Answer 3

• Brassica oleracea and Brassica rapa
• Selected for (i) proliferation of leaves and (ii) proliferation of stem base tissues.
• Produced Cabbage, Chinese Cabbage and Kohlrabi, Turnip respectively.

Question 4

Give 6 Common Crop Traits Selected During Domestication

Answer 4

• Determinate growth
• Synchronous ripening
• Reduced bitterness
• Larger seed and fruit size
• Seedlessness
• Grain retention

Question 5

Explain some of the genetic insights from work done on Teosinte and Maize. From who’s lab?

Answer 5

• Few gene loci account for 90% of difference.
• John Doebley’s lab.

Question 6

Give data on how many crops are used by humans out of how many total crops.

Answer 6

• 400,000 species on Earth
• 20,000 ever used for human food
• 30 provide most the world’s food
• 3 crops (rice, wheat, maize) dominate food supply

Question 7

What are some of the economic benefits to understanding plants?

Answer 7

• Pathways unique to plants produce valuable compounds.
• Research focuses on transferring these pathways to microbes or optimising them in plants for higher yields.
• Plants offer scalable, cost-effective options for bioproduction + circular economies.

Question 8

Give an example of an organelle that is under engineering research for crop improvement.

Answer 8

• Chloroplasts targeted for metabolic engineering.
• E.g. astaxanthin pathway introduced to Nicotiana tabacum to produce valuable astaxanthin [Yinghong Lu, 2017]
• Astaxanthin feeds salmon + trout to give red colour.

Question 9

Give an example of where gene knockdown has been recently used for crop improvement.

Answer 9

• Recently domesticated Brassica napus (Oilseed rape) can still undergo dehiscence.
• Similar to A. thaliana, with known shattering mechanisms.
• CRISPR/Cas9 used to knockdown Shatterproof and Indehiscent genes.

Question 10

Give an example of how the editing of regulatory loops can be used for crop improvement.

Answer 10

• CRISPR allow for precise modifcations in regulatory genes.
• Analysis of genetic differences between modern tomatoes and wild Peruvian Solanum pimponellifolium inform editing.
• Tomato and unimproved Physalis (related) edited and optimised.

Question 11

Give an example of another regulatory target of gene editing.

Answer 11

• Engineering metabolic pathway feedback using targeted mis-regulation to amplify or reduce gene-regulated processes in
  crops.
• E.g. manipulating TFs to engineer cell wall composition for improved bioenergy feedstocks.
• E.g. regulatory network in Arabidopsis engineered to decrease lignin biosynthesis and increase cellulose content.

Question 12

Sum up the bigger picture of this in a global context.

Answer 12

• Gene editing technologies + more understanding can lead to rational design of improved crop traits, addressing global agricultural challenges.