Expression of phenylalanine ammonia-lyase gene during tracheary-element differentiation from cultured mesophyll cells ofZinnia elegans L. |
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Authors: | Lin Q Northcote D H |
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Institution: | (1) Department of Biochemistry, University of Cambridge, Tennis Court Road, CB2 1QW Cambridge, UK;(2) Present address: Department of Plant Pathology, Rothamstead Experimental Station, AL5 2JQ Harpenden, Herts., UK |
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Abstract: | Expression of the phenylalanine ammonialyase (PAL) gene during tracheary-element differentiation was studied in mesophyll
cell-suspension cultures ofZinnia 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 theZinnia 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.
We thank Bejing Agricultural University, the Lundgren Research fund (University of Cambridge) and an ORS award for financial
support. |
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Keywords: | Auxin (xylem differentiation) Cytokinin (xylem differentiation) mRNA induction (phenylalanine ammonia-lyase) Phenylalanine ammonia-lyase (mRNA induction) Xylem differentiation |
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