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

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.