Disruption of Arabidopsis CHY1 Reveals an Important Role of Metabolic Status in Plant Cold Stress Signaling
a Department of Botany and Plant Science, 2150 Batchelor Hall, University of California at Riverside, Riverside, CA 92521, USA
b Department of Biology, University of Missouri-St Louis, St Louis, MO 63121, USA
c Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005, USA
d Present address: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
e Present address: Department of Life Science, Sogang University, Seoul 121-742, South Korea
1 To whom correspondence should be addressed. E-mail jian-kang.zhu{at}ucr.edu, fax 951-827-7115, tel. 951-827-7117.
To study cold signaling, we screened for Arabidopsis mutants with altered cold-induced transcription of a firefly luciferase reporter gene driven by the CBF3 promoter (CBF3-LUC). One mutant, chy1-10, displayed reduced cold-induction of CBF3-LUC luminescence. RNA gel blot analysis revealed that expression of endogenous CBFs also was reduced in the chy1 mutant. chy1-10 mutant plants are more sensitive to freezing treatment than wild-type after cold acclimation. Both the wild-type and chy1 mutant plants are sensitive to darkness-induced starvation at warm temperatures, although chy1 plants are slightly more sensitive. This dark-sensitivity is suppressed by cold temperature in the wild-type but not in chy1. Constitutive CBF3 expression partially rescues the sensitivity of chy1-10 plants to dark treatment in the cold. The chy1 mutant accumulates higher levels of reactive oxygen species, and application of hydrogen peroxide can reduce cold-induction of CBF3-LUC in wild-type. Map-based cloning of the gene defective in the mutant revealed a nonsense mutation in CHY1, which encodes a peroxisomal β-hydroxyisobutyryl (HIBYL)–CoA hydrolase needed for valine catabolism and fatty acid β-oxidation. Our results suggest a role for peroxisomal metabolism in cold stress signaling, and plant tolerance to cold stress and darkness-induced starvation.
Key Words: Cold stress • signal transduction • gene regulation • CHY1 • β-hydroxyisobutyryl–CoA hydrolase
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