Induction of phenylalanine ammonia-lyase and 4-coumarate:CoA ligase mRNAs in cultured plant cells by UV light or fungal elicitor

Abstract

The mRNA encoding 2 enzymes of phenylpropranoid metabolism, phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) and 4-coumarate:CoA ligase (4CL; EC 6.2.1.12), were induced in cultured parsley cells (Petroselinum hortense) either by irradiation with UV light or by treatment with elicitor, a cell-wall fraction of the fungus Phytophthora megasperma f. sp. glycinea. 2-Dimensional gel electrophoresis of the encoded PAL and 4CL proteins revealed that the mRNA induced by either treatment were very similar if not identical. RNA blot hybridization with cDNA [complementary DNA] complementary to these mRNA was used to measure changes in the mRNA amounts at various times after either treatment. Total cellular PAL and 4CL mRNA amounts increased coordinately after UV irradiation to a maximum at 7 h and then decreased to uninduced levels by 30 h with the same kinetics as observed previously for the changes in the translational activities. Treatment with the fungal elicitor also caused coordinated, but more rapid, changes in PAL and 4CL mRNA translational activities, with a sharp peak occurring 3 h after the addition of elicitor. Corresponding changes in mRNA amounts were observed only for 4CL, whereas the amount of PAL mRNA continued to increase at least up to 20 h after elicitor addition. Parsley cells may respond to UV irradiation or addition of fungal elicitor by increased rates of transcription of genes involved in the synthesis of compounds related to UV or disease resistance, respectively.