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Plant fertilization and transgenic plants
How does fertilization occur in plants?
How do you make a transgenic plant?
Flowering plant life cycle
Meiosis in female produces four megaspores. One of these makes the gametophyte.
Female gametophyte: Megaspore nucleus divides three times to produce 8 nuclei.Then the gametophyte cellularizes.
Male gametophyte: pollen grains
Fertilization:Pollen tube fuses with a synergid.Sperm cells are released.
Fertilization: The egg is fertilized to produce the embryo. The central cell is fertilized to produce the triploid endosperm
embryo
endosperm(central cell)
ovule
transmitting tract
Pollination viewed with pollen-specific GUS marker line
(from Johnson et al., 2004, Genetics 168: 971-982)
Pollen tube attraction to Tourenia micropyle
Higashiyama and Hamamura (2008) Sexual Plant Reproduction 21: 17-26
Pollen tube attraction to Tourenia fournerii micropyle
(movie)
Higashiyama and Hamamura (2008) Sexual Plant Reproduction 21: 17-26
Small peptide applied at time 0
(Fluorescent dye allows visualization of possible gradient)
(Okuda et al. (2009) Nature 458: 357-361)
Small peptides made in the synergids attract pollen
(Okuda et al. (2009) Nature 458: 357-361)
The peptides are needed to attract pollen
Knock down expression of peptide genes in embryo sacs
Double fertilization
Sperm nuclei marked with red fluorophore, female nuclei with green
(movie)
(Berger et al. (2008) Trends in plant Science 13: 437-443)
Making transgenic plants
Agrobacterium tumefaciens causes crown gall tumors
Making transgenic plants
Agrobacterium-mediated plant transformation
kanamycin resistant
Gene conferring kanamycin resistance
your favorite gene
Making transgenic plants
Regenerating plants from cultured (transformed) cells
Agrobacterium-mediated Arabidopsis transformation
Select among progeny seeds for transgenic plants (herbicide or antibiotic resistance)
Dip Arabidopsis flowers in solution of engineered Agrobacterium
Examples of transgenic plants
Widely grown:
Herbicide resistant
Pest resistant
Other ideas:
Improved nutrition (golden rice)
Delayed ripening
Salt tolerance
Phytoremediation (decontaminate soils)
http://www.isaaa.org/Resources/Publications/briefs/35/executivesummary/default.html
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