Building Better Seeds

Question 1

Explain why artificial seeds are important for biotechnology

Answer 1

Organogenesis and embryogenesis for micropropagation is labour intensive, and is likely to experience losses at each stage. Artificial seeds allow synchronised harvest, mass propagation of elite clones, reduced costs and improved long term storage.

Question 2

In which ways are the development of a somatic embryo similar to that of a zygotic embryo?

Answer 2

Both heavily rely on the expression of genes to regulate embryo development. Auxin regulates the early stages of somatic embryogenesis whilst cytokinins become important in the later stages (as in zygotic embryogenesis). So similar in terms of genetic (WUSCHEL genes) and hormonal regulatory pathways.

Question 3

How is a somatic seed developed?

Answer 3

1. Induction of somatic embryogenesis - An embryo is produced via somatic embryogenesis.
2. Maintenance and proliferation of embryogenic cultures
3. Regeneration of embryos
4. Induction of desiccation tolerance - Desiccation tolerance is then induced via exposure to specific plant hormones (abscisic acid) and the dehydrins are expressed.
5. Encapsulation - The embryos are then suspended in a liquid culture medium that contains nutrients. The embryo will then be encapsulated using alginate.

Question 4

What are LEAs and what are their main functions?

Answer 4

LEAs are late embryo-abundant proteins that are produced by the expression of the dehydrin genes.
They have three main functions:
1. Sequestering function
2. Membrane protection
3. Protein and enzyme protection

Question 5

What genes are critical for zygotic embryo development, and how are they key in somatic embryo formation?

Answer 5

WOX genes - encode a family of transcription factors that play a key role in meristem formation
WUS genes - regulator of shoot meristem organisation
WOX5 genes - regulator of root meristem organisation

Question 6

Describe the process of embryogenesis