Plant Physiol, August 2000, Vol. 123, pp. 1553-1560
Trivalent Ions Activate Abscisic Acid-Inducible Promoters
through an ABI1-Dependent Pathway in Rice
Protoplasts1
Dik
Hagenbeek,
Ralph S.
Quatrano, and
Christopher D.
Rock*
Department of Biology, Hong Kong University of Science and
Technology, Clear Water Bay, Kowloon, Hong Kong, China (D.H.,
C.D.R.); and Department of Biology, Washington University, St.
Louis, Missouri 63130-4899 (R.S.Q.)
The plant hormone abscisic acid (ABA) mediates many vital processes
in plant growth and development, including seed dormancy, cell
division, water use efficiency, and adaptation to drought, salinity,
chilling, pathogen attack, and UV light. Our understanding of ABA
signal transduction is fragmentary and would benefit from specific and
facile probes of the process. Protoplasts from rice (Oryza
sativa L. cv IR54) embryonic suspension cultures cotransformed with effector plasmids encoding the maize (Zea mays)
VIVIPAROUS1 cDNA and/or the Arabidopsis dominant
negative mutant (abi1-1) ABA-insensitive cDNA
demonstrated genetic interactions of VIVIPAROUS1 and
abi1-1 in transactivation of the ABA-inducible
HVA1 promoter from barley (Hordeum
vulgare), suggesting the mechanisms of these effectors are
conserved among monocots and dicots. Trivalent ions have been shown to
act as an effector of gene expression in plants and animals, although
the mechanism of action is unknown. We show in two complementary
transient ABA-inducible gene expression assays (
-glucuronidase and
luciferase enzymatic activities and quantitative flow cytometry of
green fluorescent protein) that trivalent ions specifically interact
with an ABI1-dependent ABA-signaling pathway leading to
gene expression. Trivalent ions mimic ABA effects on gene expression
and may be a useful tool to study ABA signaling.
1
This work was supported by the Hong Kong
Research Grants Council's Competitive Earmarked Research Grant (no.
HKUST-6173/97M to C.D.R.).
*
Corresponding author; e-mail borock{at}ust.hk; fax 852-2358-1559.
© 2000 American Society of Plant Physiologists
