Genetically Modified Plants

2. Genetically Modified Plants • Biotechnology: underlying science • Potential Risks vs. (Potential) Benefits Assigned Reading: Chapter 10.5

3. Types of GMOs? artificial selection and traditional breeding, transgenic organisms, other approaches, targeted mutagenesis, gene introgression, ? Old Science Humans (~30,000 years) Humans (~30 years) Bacteria (eons) Humans (~15 years) Bacteria (eons) Genetically Modified Organisms

4. Desirable Agronomic Traits(traditional or modern) • Increased yields, more nutritious, quality, etc., • More resistant to pestilence, weeds, water and nutrient deprivations, • Ability to withstand marginal growth conditions, • and thrive in new environmental ranges, • Profit.

5. Traditional Breeding • technology is not essential, • limited by species boundaries, • all genes/traits are mixed. ~25,000 genes ~45,000 genes

6. Introgression …incorporation of genes of one genome into the genome of another cultivar, • standard breeding techniques are laborious (if possible at all), • genomics and related sciences greatly accelerates standard breeding techniques.

7. Genome Era Traditional Breeding Wild tomato Cultivar w/ 1 wild gene replacement

8. Genetic Bottlenecks and Seed Preservation

9. Introgression GMO

10. Transgenic Plants • based on DNA technology, • single genes/traits can be transferred, • species boundaries are not limiting.

11. ...uses tools of molecular genetics, • - i.e. applied bacteria and virus genetics. Agrobacterium tumefaceins - or - How are GMOs generated? insert into plant …via biolistics

12. Biolistics

13. Kalanchoe Stem w/ infection. Natural soil bacterium that infects plants,hosts: 160 Genera,families: > 60,effect; poor growth, low yield. Agrobacterium tumefaciens

14. Ti-Plasmid Transfer-DNA Plant Cells Lab T-DNA Out: Ti genes, opine genes, In: DNA of choice. Nature Ti: tumor inducing Plasmid: extrachromosomal DNA evolved for genetic transfer. Hormone genes Opines genes Agrobacterium Any Gene Selectable Markers, etc

15. transform, select for agro with T-DNA Agrobacterium infect plant, select for plants with T-DNA Plant chromosome with T-DNA insert. T-DNA (Transfer DNA) • …with gene of interest, • b-carotene, • herbicide resistance, etc.. Construct T-DNA

16. T-DNA (Transfer DNA) selection genes • …gene of interest, • b-carotene, • herbicide resistance, etc.. virulence genes Construct T-DNA Virulence genes: facilitate Agro infection, T-DNA transfer, • not usually transferred in commercial applications, Selection genes (2+): used to identify transgenics, • usually antibiotic or herbicide resistance, etc. (i.e. only the organisms with the T-DNA live in a selection experiment), Gene of interest: protein coding region, plus a “promoter”.

17. Promoters Control Expression Transgenes must be expressed in order to function, Promoters control where, when and how much protein is produced. Foreign DNA is common (via nature) in most genomes,

18. gene (kilobases) ...ata cgt act atc... ||| ||| ||| ||| ...tat gca tga tag... ...ttaggttctatc... |||||||||||| ...aatccaagatag... promoter specific sequences. protein coding Gene Structure chromosome (megabases)

19. General Promoter: all tissues, all the time. Vegetative Promoter: no flower, no fruit expression. Root Promoter: only root expression. Promoter Specifies Expression

20. Expression = Protein Production Protein and protein functions only present in tissue with active promoter. Tissue Specific Expression Time Specific Expression “Suicide” Promoters, etc.

22. Brief History of Transgenic Organisms • Transgenic E. coli, • not demonstratively dangerous, • demonstratively beneficial (probably). • Transgenic virus, • not demonstratively dangerous, • demonstratively beneficial (probably). • Transgenic plants, • demonstratively dangerous? (not yet), • demonstratively beneficial (?).

23. Potential Risks • Risk of invasion. • Direct nontarget Effects • Indirect nontarget Effects. • New Viral Diseases. • Variability and Unexpected Results.

24. Potential Risks(risk of invasion) • 50,000 invaders in USA the old fashioned ways, • self-sustaining cultivars, • low anticipated risk, • hybridization with (native) neighbors, • transgene introgression, • introgression of domestic cultivar genes with natives has occurred, resulting in negative impacts on native species, • time lags.

25. Direct (nontarget) • Risk to non-target species, • pollinators, • passers-by, • soil ecosystems, • decomposition rates, • carbon cycle, • nitrogen cycle.

26. Indirect (nontarget) • kill weeds = kill species that live “on” or eat the weeds, • bioaccumulation, • nontarget species eat plants, store toxins, • those species are eaten, amassing the toxin, • on up the food chain. Bee on Red Clover.

27. New Viral Diseases • virus resistant plants promote virulent strains, • mutations, • recombination, • heteroencapsulation, • virus move genes from one organism to another, • not presently a risk, but a potential risk.

28. Variability and Unexpected Results • time scale, • numbers, • environmental and cultivar differences, • application, culture and consistency.

29. Other Issues • Economic hegemony of GMP seed producing countries, companies, • Cultural shifts in farming due to the introduction of GMOs, • Potential allergies to genetically modified crops, • The preservation of natural genetic crop-lines, • The lack of an adequate risk assessment methodology to quantify unintended ecological consequences.

30. The Precautionary Principle

31. Works great Bad Environmental Consequences Increase Carrying Capacity for Humans Human Population Growth • Negative impacts on, • select species, • crops, • ecosystems, • etc. • Negative impacts on, • select species, • crops, • ecosystems, • etc. Biotechnology in General Scenario 1 Scenario 2

32. pBacR: piggyback vector, transposon derived 3xP3-EGFP-S40: Green fluorescent protein, eye specific promoter AgCP promoter: mosquito promoter, activated by blood feast. Signal: peptide sequence that sends protein to the midgut. SM14: SM1 DNA sequence repeated 4 times, linked Transgenic Construct