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USEFUL MUTANTSUSEFUL MUTANTS
Heritable changes can result in a useful novel phenotype, i.e., a new allele.
Other Kinds
Some “not bad” Mutants
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.
Ornamental Corn
Single gene mutations in the anthocyanin (pigment) production pathway lead to the colored kernels we see on an ear of Indian corn.
Waxy Corn
A mutation in the waxy gene is used in production of tapioca and other gelling starch products.
High-lysine Corn
A mutation in the opaque2 gene results in increased levels of the essential amino acid, lysine. Quality Protein Maize (QPM).
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.
And of course --
Disease resistance Insect resistance
Glossy mutants Flowering time Cytoplasmic male sterility Nutritional changes “Value-added” changes
Mutations and Co-evolution
Variations usually exist in nature. Co-existing species experience mutual selection.
Domestication by Culture
Suppression of ‘Wild’ Traits Seed scattering Mixed timing Hard-shelled seeds
Mutation/Selection of ‘Desired’ Traits Packaging Convenience Storability Processing
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.
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
Dwarf Wheat Opened Doors
New Wheats a la Nature
Deliberate employment of diversity in collections. Crosses of AABB with diverse DD and others.
http://www.maizegdb.org/cgi-bin/imagebrowser_phenotypes.cgi
Mutant Images for Maize
Ramosa tassel and ear
Terminal ear1
Teopod2, Tunicate1
White pollen1 (bursting)
Virescent1
Directed Transposon Tagging
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.
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)
Perform co-segregation analysis to identify transposon linked to your mutant phenotype.
all Yellow seed (y1/Y1)
si1 y1/Si1 Y1 (99.99%) Normal Phenotypesi1 y1/si1-mum Y1 (rare mutant 1/10000)
X Si1 y1/Si1 y1
(normal tassel)Southern Blot Hybridized with Mu1 Probe
(silky tassel (si1/si1-mum))
M0M0
M1M1
bz1*bz1*
sh1*sh1*
C1 sh1 bz1C1 sh1 bz1Lyophilize
d leaf disks
Lyophilized leaf disks
DNADNA
M2M2
Random intermating
Random intermating
Bulk SeedBulk SeedMinimum
criteria: ≥50 M2 seed with
≥60% germination
Minimum criteria: ≥50 M2 seed with
≥60% germination
Maize Genetics
Stock Centerfor
distribution
Maize Genetics
Stock Centerfor
distribution
Grow-outs
open to the
general public
Grow-outs
open to the
general public
Forward screens
for specific traits of interest
Forward screens
for specific traits of interest
M3M3
EMS treat pollenEMS treat pollen
TILLING = Targeting Induced Limited Lesions IN Genomes
c1 Sh1 Bz1c1 Sh1 Bz1
Make mutant populationMake mutant population
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
IR700 IR800
200 bp
95bp
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.