First published online September 23, 2005; 10.1104/pp.105.065045
Plant Physiology 139:722-733 (2005)
© 2005 American Society of Plant Biologists
DEVELOPMENT AND HORMONE ACTION
Protein Geranylgeranyltransferase I Is Involved in Specific Aspects of Abscisic Acid and Auxin Signaling in Arabidopsis1
Cynthia D. Johnson2,
S. Narasimha Chary2,3,
Ellen A. Chernoff,
Qin Zeng,
Mark P. Running and
Dring N. Crowell*
Department of Biology, Indiana University-Purdue University, Indianapolis, Indiana 462025132 (C.D.J., S.N.C., E.A.C., D.N.C.); and Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (Q.Z., M.P.R.)
Arabidopsis (Arabidopsis thaliana) mutants lacking a functional ERA1 gene, which encodes the -subunit of protein farnesyltransferase (PFT), exhibit pleiotropic effects that establish roles for protein prenylation in abscisic acid (ABA) signaling and meristem development. Here, we report the effects of T-DNA insertion mutations in the Arabidopsis GGB gene, which encodes the -subunit of protein geranylgeranyltransferase type I (PGGT I). Stomatal apertures of ggb plants were smaller than those of wild-type plants at all concentrations of ABA tested, suggesting that PGGT I negatively regulates ABA signaling in guard cells. However, germination of ggb seeds in response to ABA was similar to the wild type. Lateral root formation in response to exogenous auxin was increased in ggb seedlings compared to the wild type, but no change in auxin inhibition of primary root growth was observed, suggesting that PGGT I is specifically involved in negative regulation of auxin-induced lateral root initiation. Unlike era1 mutants, ggb mutants exhibited no obvious developmental phenotypes. However, era1 ggb double mutants exhibited more severe developmental phenotypes than era1 mutants and were indistinguishable from plp mutants lacking the shared -subunit of PFT and PGGT I. Furthermore, overexpression of GGB in transgenic era1 plants partially suppressed the era1 phenotype, suggesting that the relatively weak phenotype of era1 plants is due to partial redundancy between PFT and PGGT I. These results are discussed in the context of Arabidopsis proteins that are putative substrates of PGGT I.
1 This work was supported by U.S. Department of Agriculture grants 0003367 and 0302151 to D.N.C. and by National Science Foundation grant IOB0344261 to M.P.R.
2 These authors contributed equally to the paper.
3 Present address: Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California, Riverside, CA 92521.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.065045.
* Corresponding author; e-mail dcrowell{at}iupui.edu; fax 3172742846.
Received May 9, 2005;
returned for revision July 9, 2005;
accepted July 18, 2005.
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