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USEFUL MUTANTS

USEFUL MUTANTS. Heritable changes can result in a useful novel phenotype, i.e., a new allele. Other Kinds. Some “not bad” Mutants. Sweet Corn.

christopher-roy
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USEFUL MUTANTS

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  1. USEFUL MUTANTS • Heritable changes can result in a useful novel phenotype, i.e., a new allele.

  2. Other Kinds

  3. Some “not bad” Mutants

  4. Sweet Corn • Single gene mutations in several different starch biosynthesis genes have been introduced into tender, flavorful corn to produce the sweet corn we eat today - • Instead of transferring sugars into starch, they accumulate ‘sweetness’. • Shrunken (Supersweet), sugary, sugary enhancer, amylose extender.

  5. Ornamental Corn Single gene mutations in the anthocyanin (pigment) production pathway lead to the colored kernels we see on an ear of Indian corn.

  6. Waxy Corn A mutation in the waxy gene is used in production of tapioca and other gelling starch products.

  7. High-lysine Corn • A mutation in the opaque2 gene results in increased levels of the essential amino acid, lysine. • Quality Protein Maize (QPM).

  8. o2, opaque endosperm: endosperm soft and opaque; high lysine content; regulates b-32 protein. Photo: seed from a selfed ear segregating for opaque kernels in transmitted light showing opaqueness of mutant kernels.

  9. And of course -- • Disease resistance • Insect resistance • Glossy mutants • Flowering time • Cytoplasmic male sterility • Nutritional changes • “Value-added” changes

  10. Mutations and Co-evolution • Variations usually exist in nature. • Co-existing species experience mutual selection.

  11. Domestication by Culture • Suppression of ‘Wild’ Traits • Seed scattering • Mixed timing • Hard-shelled seeds • Mutation/Selection of ‘Desired’ Traits • Packaging • Convenience • Storability • Processing

  12. Domestication in Wheat • DIVERGENCE, CROSSING, SELECTION • Earliest cultivated and wild wheat, with the 7-chromosome A genome (left), crossed with another, with the B genome, (third) about 8000 BC. The result was durum wheat (emmer = PASTA WHEAT), fourth in this photo. Emmer crossed with wild goat grass (fifth) and gave rise to the staff of life (BREAD WHEAT), sixth. The combination, AABBDD, 7x3 = 21 chromosomes, is productive and high in food quality.

  13. Dwarf Wheat Opened Doors • Ninetieth birthday of the Father of the Green Revolution, Nobel Peace Prize Laureate Norman Borlaug http://www.cimmyt.org/english/webp/support/news/borlaug_90.htm

  14. New Wheats a la Nature • Deliberate employment of diversity in collections. • Crosses of AABB with diverse DD and others.

  15. Mutant Images for Maize • http://www.maizegdb.org/cgi-bin/imagebrowser_phenotypes.cgi

  16. Ramosa tassel and ear

  17. Terminal ear1

  18. Teopod2, Tunicate1

  19. White pollen1 (bursting)

  20. Virescent1

  21. Directed Transposon Tagging • An example---cloning the male sterile silky1 (si1) gene using Mutator. • si1 y1/si1 y1 X Si1 Y1/Si1 Y1, Mu-active • (white seed/silky tassel) X (Yellow seed/normal tassel) all Yellow seed (y1/Y1) si1 y1/Si1 Y1 (99.99%) Normal Phenotype si1 y1/si1-mum Y1 (rare mutant 1/10000) X Si1 y1/Si1 y1 Yellow seed have tagged si1 allele (Si1 y1/si1-mum Y1) Grow plants from yellow seed and backcross to si1 y1/si1 y1. Plant out seeds, score for silky vs normal tassel phenotype. Prepare DNA from leaves of each type. Perform co-segregation analysis to identify transposon linked to your mutant phenotype.

  22. Southern Blot Hybridized with Mu1 Probe (normal tassel) (silky tassel (si1/si1-mum))

  23. TILLING = Targeting Induced Limited Lesions IN Genomes Make mutant population Maize Genetics Stock Center for distribution EMS treat pollen M2 c1 Sh1 Bz1 bz1* Bulk Seed Grow-outs open to the general public Minimum criteria: ≥50 M2 seed with ≥60% germination sh1* DNA Forward screens for specific traits of interest M3 C1 sh1 bz1 M1 Lyophilized leaf disks Random intermating M0

  24. DNA prepared and equal amounts of each sample arrayed to microtiter wells, then these 8-fold pooled IR-labeled primers create double end-labeled fragments

  25. 200 bp 95bp IR700 IR800 Bands of complementary size are visible, one in each image channel, corresponding to singly end-labeled fragments cleaved by CELI at the mutation site. Mutant individuals identified from pools, sequenced. Information and analysis returned to User, along with Stock Center numbers for ordering seed.

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