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)

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