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 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.
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 Phenotype si1 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 M0M0 M1M1 M1M1 bz1* sh1* C1 sh1 bz1 Lyophilized leaf disks DNA M2M2 M2M2 Random intermating Random intermating Bulk Seed Bulk Seed Minimum criteria: ≥50 M 2 seed with ≥60% germination Maize Genetics Stock Center for distribution Maize Genetics Stock Center for distribution Grow- outs open to the general public Forward screens for specific traits of interest M3M3 M3M3 EMS treat pollen TILLING = Targeting Induced Limited Lesions IN Genomes c1 Sh1 Bz1 Make 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
IR700IR800 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.