Plant and Cell Physiology Advance Access originally published online on June 13, 2007
Plant and Cell Physiology 2007 48(7):1061-1071; doi:10.1093/pcp/pcm076
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Phytochrome Chromophore Deficiency Leads to Overproduction of Jasmonic Acid and Elevated Expression of Jasmonate-Responsive Genes in Arabidopsis
1State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, PR China
2Graduate School of Chinese Academy of Sciences, Beijing 100039, PR China
3The State Key Laboratory of Crop Biology, Agronomy College, Shandong Agricultural University, Taian 271018, PR China
4Institute of Insect Sciences, Zhejiang University, Hangzhou 310029, PR China
*Corresponding author: E-mail, cyli{at}genetics.ac.cn; Fax, +8610-6487-3428.
| Abstract |
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An Arabidopsis mutant line named hy1-101 was isolated because it shows stunted root growth on medium containing low concentrations of jasmonic acid (JA). Subsequent investigation indicated that even in the absence of JA, hy1-101 plants exhibit shorter roots and express higher levels of a group of JA-inducible defense genes. Here, we show that the hy1-101 mutant has increased production of JA and its jasmonate-related phenotype is suppressed by the coi1-1 mutation that interrupts JA signaling. Gene cloning and genetic complementation analyses revealed that the hy1-101 mutant contains a mutation in the HY1 gene, which encodes a heme oxygenase essential for phytochrome chromophore biosynthesis. These results support a hypothesis that phytochrome chromophore deficiency leads to overproduction of JA and activates COI1-dependent JA responses. Indeed, we show that, like hy1-101, independent alleles of the phytochrome chromophore-deficient mutants, including hy1-100 and hy2 (CS68), also show elevated JA levels and constant expression of JA-inducible defense genes. We further provide evidence showing that, on the other hand, JA inhibits the expression of a group of light-inducible and photosynthesis-related genes. Together, these data imply that the JA-signaled defense pathway and phytochrome chromophore-mediated light signaling might have antagonistic effects on each other.
Keywords: Arabidopsis - hy1 - hy2 - Jasmonic acid - Light signaling—Phytochrome chromophore
Abbreviations: ALA, aminolevulinic acid; BAC, bacterial artificial chromosome; bHLH, basic helix–loop–helix; BV, biliverdin; CAPS, cleaved amplified polymorphic sequence; coi1, coronatine insensitive1; EMS, ethyl methanesulfonate; GC-MS, gas chromatography–mass spectrometry; GUS, ß-glucuronidase; hy1 and hy2, long hypocotyl mutant1/2; JA, jasmonic acid; MeJA, methyl jasmonic acid; phyA and phyB, phytochrome photoreceptor A/B; RT–PCR, reverse transcription–PCR; VSP1, vegetative storage protein1.
5These authors contributed equally to this work.
(Received April 4, 2007; Accepted June 10, 2007)
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