EXPRESSION OF PHENYLALANINE AMMONIA-LYASE GENE DURING TRACHEARY-ELEMENT DIFFERENTIATION FROM CULTURED MESOPHYLL-CELLS OF ZINNIA-ELEGANS L

Expression of the phenylalanine ammonialyase (PAL) gene during tracheary-element differentiation was studied in mesophyll cell-suspension cultures of Zinnia elegans. Dose-response curves of benzyladenine (BA) and α-naphthaleneacetic acid (NAA) were obtained for the cultures in order to achieve the highest percentage of differentiation. The optimal concentrations of BA and NAA were 0.1 mg·l-1 and 0.06 mg·l-1, respectively, which normally stimulated about 40% differentiation by 96 h of culture. The effects of the same ratio but different amounts of BA and NAA on tracheary-element formation have been tested and the results indicate that the absolute amounts of BA and NAA rather than the ratio of them were important for tracheary-element formation in the Zinnia cultures. The cells when cultured in the presence of 0.001 mg·l-1 of BA and 0.06 mg·l-1 of NAA expanded and divided but did not differentiate. The level of PAL activity, synthesis of PAL protein and the level of PAL mRNA peaked during 72 to 96 h when lignin was actively deposited. This indicated that the PAL gene was temporally and preferentially expressed in association with the lignification during tracheary-element differentiation and thus it can be regarded as a molecular marker for the process. © 1990 Springer-Verlag.