Plant protoplasts as genetic tool: selectable markers for developmental studies.

Protoplasts have usually been presented as a methodological tool. Even as such, they make possible an impressive array of applications in plant biology. Here we report on the use of protoplast-derived selectable markers in the study of several disturbed genetic systems with obvious effects on plant development: (1) auxotrophic mutants and the control of amino acid biosynthesis and transport in vegetative and reproductive tissues; (2) introgression of alien genetic information across phylogenetic boundaries by protoplast fusion, a consequence of controlled dedifferentiation-redifferentiation processes and attenuated incompatibility reactions in cultured cells; (3) expression (in)stability of foreign genes in transgenic plants during successive meiotic generations and in crosses between independent transformants.