THE PLANT CELL, Vol 3, Issue 6 573-582, Copyright © 1991 by American Society of Plant Biologists
Phytochrome Control of the tms2 Gene in Transgenic Arabidopsis: A Strategy for Selecting Mutants in the Signal Transduction Pathway
G. A. Karlin-Neumann, J. A. Brusslan and E. M. Tobin
Department of Biology and Molecular Biology Institute, University of California, Los Angeles, California 90024-1606
Introduction of the tms2 gene from Agrobacterium tumefaciens into
Arabidopsis thaliana yields transgenic seedlings with a new selectable
phenotype: the seedlings are strongly growth inhibited on micromolar
concentrations of auxin amide substrates that do not significantly affect
wild-type seedlings. The tms2 gene encodes an amidohydrolase that catalyzes
the conversion of biologically inactive auxin amides into active auxins,
which are toxic to plants at elevated concentrations. In the absence of
exogenous substrate, tms2+ transgenic seedlings grow normally and are
fertile. When grown on auxin amides, both etiolated and green tms2+
seedlings exhibit a variety of dose-dependent auxin toxicity effects. tms2
mRNA and the encoded amidohydrolase activity are both detectable in
transgenic but not in wild-type seedlings, demonstrating that a cognate
activity is lacking in wild-type Arabidopsis. Furthermore, when the
introduced tms2 gene is fused to the Arabidopsis cab140 promoter, the tms2
RNA and its encoded amidohydrolase activity and, thus, the conditional
lethal phenotype can be modulated by phytochrome action. The tms2 gene can,
therefore, serve as a regulatable selectable marker in Arabidopsis that
should be useful in isolation of trans-regulatory mutants that have lost
the imposed regulation of tms2 gene activity.
