Intergeneric nuclear gene transfer between somatically and sexually incompatible plants through asymmetric protoplast fusion

Abstract

A stable intergeneric transfer of nuclear genes from Physalis minima into the genome of Datura innoxia has been achieved through asymmetric protoplast fusion. No hybrid plants could be obtained from these species either by traditional methods of sexual breeding or by somatic hybridization via fusion of protoplasts containing complete nuclear genomes. The incompatibility barriers were bypassed by the fusion of highly X-irradiated (LD100) wild-type Physalis with nuclear albino mutant Datura protoplasts. In this intergeneric reconstruction, 1.15% of the total heterokaryons restored the chlorophyll synthesis in their regenerants. Two representative transformed lines, TRL-A and TRL-D, were further characterized, showing 0.43–0.78 pg. additional nuclear DNA (4.45–8.07% nuclear DNA of P. minima). Since chromosomes of the species of Datura and Physalis were distinguishable, the mitotic complement of the transformed regenerants showed only 3 and 1 chromosomes of the donor in tetraploid (2n=48) and octoploid (2n=96) genomes of the recipient, respectively. The introduction and expression of limited genes of Physalis in Datura have also been confirmed by the allelic expression of various isoenzymes. Such stable gene transfer via asymmetric fusion of protoplasts has been discussed in relation to its application in the genetic manipulation of plants.