Various breeds of plants have
been produced and used in agriculture. Methods of breeding technology include gene modification (gene
transfer and genome editing), chromosomal set manipulation, utilization
of nuclear/cytoplasmic hybrids, and the induction of chimeric individuals, which are
collectively called “developmental engineering.” Plant cells improved by
developmental engineering techniques can be cultured to transform them into
individuals and then be used as agricultural varieties, because of their “pluripotency” of single plant cells that allows them to differentiate into various cell types.. What about animals? At present, a single animal cell cannot be
cultured to produce an individual, and gametes (eggs/sperm)
must be generated and undergo the process of fertilization. Therefore, even if
an individual possesses a useful gene, it cannot be utilized without going
through the gametes. Individuals, of course, can be generated by nuclear
transplantation, but the success rate is very low. However, it has been shown
that if a “germ-line chimera” is generated by transplanting germ-line cells
(donors), which differentiate into eggs and sperms, into another individual
(host), then the gamete of the donor can be generated. This method, called “germ-line
chimera,” may lead to the improvement of fish breeds, and the Nanae Freshwater Station of Hokkaido University is researching developmental engineering using various fishes as materials.
