Functional Studies of FIN219 in the Integration of Far-Red Light and Jasmonate Signaling in Arabidopsis
Date Issued
2011
Date
2011
Author(s)
Wang, Jhy-Gong
Abstract
Chapter 1
FAR-RED INSENSITIVE 219 (FIN219) in Arabidopsis is involved in phytochrome A-mediated far-red (FR) light signaling. Previous genetic studies revealed that FIN219 acts as an extragenic suppressor of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). However, the molecular mechanism underlying the suppression of COP1 remains unknown. Here, we used a transgenic approach to study the regulation of COP1 by FIN219. Transgenic seedlings containing ectopic expression of the FIN219 N-terminal domain in wild-type Columbia (named NCox for the expression of the N-terminal coiled-coil domain and NTox for the N-terminal 300 amino-acid region) exhibited a dominant-negative long-hypocotyl phenotype under FR, reflected as reduced photomorphogenic responses and altered levels of COP1 and HY5. Yeast two-hybrid, pull-down, and bimolecular fluorescence complementation assays revealed that FIN219 could interact with the WD-40 domain of COP1 and with its N-terminal coiled-coil domain through its C-terminal domain. Further in vivo coimmunoprecipitation study confirms that FIN219 interacts with COP1 under continuous FR light. Studies of the double mutant fin219-2/cop1-6 indicated that HY5 stability requires FIN219 under darkness and FR light. Moreover, FIN219 levels positively regulated by phytochrome A can modulate the subcellular location of COP1 and are differentially regulated by various fluence rates of FR light. We concluded that the dominant-negative long-hypocotyl phenotype conferred by NCox and NTox in a wild-type background was caused by the misregulation of COP1 binding with the C terminus of FIN219. Our data provide a critical mechanism controlling the key repressor COP1 in response to FR light.
Chapter 2
Photomorphogenic development requires the synergistic integration of light signaling and phytohormones to confer plants with the ability to perceive light energy and signals for survival in environments. Previous report has suggested that FIN219 plays a dual role with enzymatic activities and a regulatory interacting protein involved in JA and FR light signaling, respectively. Here, we showed that the coi1-16 mutant exhibited a long-hypocotyl phenotype in various light conditions and influenced the expression of light-regulated genes under FR. The levels of FIN219 were dependent on COI1 and negatively feedback regulated by coronatine treatment under FR. Furthermore, GUS-COP1 overexpressed transgenic seedlings (GUS-COP1ox) were used for studying the regulation of COP1 protein in MeJA and coronatine treatments. Under FR, the COP1 levels in wild-type Col, fin219-2, and GUS-COP1ox were reduced by MeJA and coronatine treatments; surprisingly, GUS-COP1 proteins were greatly decreased in MeJA and coronatine treatments. Besides, exogenous jasmonates highly induced anthocyanin accumulation, which was dependent on HY5 protein levels. Thus, we propose that COP1 may play a vital role in the modulation of the integration between light and JA signaling pathways.
Chapter 3
Bacterial wilt in tomato caused by Ralstonia solanacearum infection is a common and widespread disease, especially in hot and humid environments. Combating the disease is difficult because of unstable host resistance and the variation and diversity of the bacterial strains. Thus, the molecular mechanisms underlying tomato resistance against Ralstonia solanacearum remain unknown. Here, we isolated a homolog of tomato Solanum lycopersicum JASMONATE RESISTANT 1 (SlJAR1), named SIJAR1-like 1 (SlJRL1) and generated transgenic tomato lines harboring an inducible promoter-driven SlJRL1 construct. SlJRL1 shares 99% amino acid identity with SlJAR1. Intriguingly, SlJRL1 showed preferential expression in aerial parts and SlJAR1 in roots. DNA gel blot analysis revealed multiple copies of SlJRL1 in the tomato genome. Transgenic tomato containing a single copy of the transgene SlJRL1 exhibited high levels of SlJRL1 expression at 2 days after dexamethasone (DEX) induction. Moreover, induction of SlJRL1 expression by DEX could delay the symptoms of tomato bacterial wilt, and efficiently reduce the amount of Ralstonia in stems, so the phytohormone jasmonic acid may participate in the resistant responses of tomato to bacterial wilt caused by Ralstonia. Therefore, transgenic tomato containing inducible expression of SlJRL1 may help further understand the molecular mechanism of tomato resistance against bacterial wilt.
Subjects
Arabidopsis
FIN219/JAR1
Far-Red Light Signaling
Jasmonate Signaling
cross-talk
Type
thesis
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