Genes involved in the dedifferentiation of plant cells.

Since the initial process of culturing tobacco mesophyll protoplasts can be considered as a model system of dedifferentiation of higher plants, the mode of expression of genes induced by auxin, a key factor in inducing dedifferentiation, has been analyzed during the regaining of meristematic activity of quiescent and differentiated tobacco mesophyll. By differential screening we have isolated three auxin-regulated genes, which we named parA, parB and parC. parA and parC, which belong to the same gene family, were supposed to play a role in transcriptional regulation upon induction by auxin, while parB encoded glutathione S-transferase. Although it was supposed that the expression of these par genes should play a pivotal role in regaining the meristematic activity of the differentiated tobacco mesophyll cells, a possibility that other less abundantly expressing genes would have been neglected in these studies has not been excluded. On the other hand, the search for genes which would be involved in maintaining cell division activity in the dedifferentiated plant cells allowed us to isolate a few genes. One of these genes, designated arcA, belonged to a beta subunit-like protein of heterotrimeric G proteins. The significance of the involvement of this gene product in maintaining the meristematic activity of plant cells cultured in vitro has been discussed.