PLANT PHYSIOLOGY , Vol 102, Issue 3 1019-1026, Copyright © 1993 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Expression Patterns of Duplicate Tryptophan Synthase [beta] Genes in Arabidopsis thaliana
K. D. Pruitt and R. L. Last
Boyce Thompson Institute for Plant Research and Section of Genetics and Development, Cornell University, Tower Road, Ithaca, New York 14853-1801
Expression of the two Arabidopsis thaliana genes encoding tryptophan
synthase [beta] (TSB1 and TSB2) was investigated by gene-specific RNA blot
hybridization and reporter gene analysis. TSB1 mRNA abundance varies in an
organ-specific manner, whereas TSB2 mRNA does not. Quantitative analysis of
transgenic plants expressing TSB1 and TSB2 translational fusions to the
[beta]-glucuronidase (GUS) gene (gusA) indicates that TSB1-GUS activity is
15-fold higher than TSB2-GUS. Histochemical analysis of these transgenic A.
thaliana plants indicates that GUS expression occurs in a developmentally
regulated manner. GUS activity driven from the TSB1 promoter is
predominantly associated with the stem, root tips, foliar vasculature,
mesophyll cells, base of developing seed pods, and tips of anther filaments
in plants 15 d and older. Sections through the vegetative stem reveal GUS
staining in all cell types including the shoot apical meristem. Although
TSB2-GUS expression is consistently detected in root tips and at the base
of developing seed pods, it is observed later in plant development than is
TSB1-GUS expression.