Naturally occurring differential drug sensitivities of cultured plant protoplasts

Plant Genetics: Increasing Crop Yield

Cell cultures of crop plants provide new opportunities to recover induced mutations likely to increase crop yield. Approaches include regulating respiration to conserve carbon fixed by photosynthesis, and increasing the nutritive value of seed protein. They depend on devising selecting conditions which only desired mutant cells can survive. Protoplast fusion offers some promise of tapping sources of genetic variation now unavailable because of sterility barriers between species and genera. Difficulties in regenerating cell lines from protoplasts, and plants from cells, still hamper progress but are becoming less severe. Recombinant DNA techniques may allow detection and selection of bacterial cell lines carrying specific DNA sequences. Isolation and amplification of crop plant genes could then lead to ways of transforming plants that will be useful to breeders.

Effect of fusicoccin on plant cell cultures and protoplasts

We have assayed the capacity of the fungal toxin fusicoccin to induce some of its characteristic effects (acidification of the medium, stimulation of K(+), and of 3-O-methyl-D-glucose uptake) in cell suspensions of Parthenocissus tricuspidata (Siebold et Zucc.) Planchon, Acer pseudoplatanus L. and Oryza sativa L., and in protoplast suspensions prepared from leaves of Nicotiana tabacum L. and Spinacia oleracea L. or from cultures of P. tricuspidata. Evidence is presented showing that all tested biological materials respond to the addition of fusicoccin. The observation that the toxin is also active on protoplasts indicates that the cell wall is not involved in the mechanism of action of fusicoccin.

Transient cycloheximide resistance in a tobacco cell line

Cylcoheximide-resistant cell lines have been recovered from tissue cultures of haploid Nicotiana tabacum at the usual mutant frequency (10(-6)). One such line, CR 4/6 was studied in detail. Resistance is based on the potential of the callus to inactive cycloheximide. The transient nature of the resistance and its association with differentiated cells indicate that the new phenotype is not due to a mutation, but rather to an alteration in gene expression.

Purification and viability determinations of plant protoplasts

A method is described for purifying plant protoplasts from cellular and subcellular debris. The procedure utilizes a density buffer containing 9.6% sodium metrizoate and 5.6% Ficoll. The use of fluorescein diacetate for assessing the viability of plant protoplasts is also reported.