Light is an important signal for regulation of plant development and metabolic processes. The photoreceptors for perception of different wavelengths of light have been characterized in Arabidopsis. Amongst these, phytochrome A (phyA), which is activated by far-red light, has emerged as the photoreceptor that plays a major role in seedling de-etiolation. Our long-term objective is to identify and characterize the signaling intermediates and mechanisms involved in transduction of the phyA signal to enable downstream developmental responses. To this end, we have identified mutants pat and lafdefective in phyA signaling. We will focus on identification of the biochemical mechanisms of action of PAT and LAF proteins and how they act with other intermediates in the phyA signaling network. In particular, we are interested in how phyA signals modify these proteins and regulate their abundance. A major focus is to study the regulation of the myb-type transcription activator, LAF1, its downstream targets and interacting proteins. We have shown that COP1, a repressor of photomorphogenesis, is an E3 ligase and can ubiquitinate LAF1 in vitro. The regulation of LAF1 by COP1-mediated ubiquitination in phyA signaling will be investigated in vitro and in transgenic plants. Conjugation of proteins by SUMO (small ubiquitin-like modifier) is emerging as an important regulatory mechanism of signaling. We have indirect evidence that LAF1 could be sumoylated as it is co-localized with COP1 in nuclear speckles, a subnuclear localization pattern associated with SUMO conjugation. We will investigate the role of sumoylation in LAF1 regulation and transmission of phyA responses. The other mutant we will analyze is pat1, which belongs to the plant-specific GRAS family of signal regulators. The possible redundant functional relationship between PAT1 and its close homolog SCL21 in phyA signaling will be examined. A third gene PAT3 and a close homolog PAT3h seem to participate only in a subset of phyA signaling responses. We will characterize the role of these genes in detail in the phyA signal transduction. Characterization of the above proteins will uncover previously unknown mechanisms of phyA signal transduction.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM044640-15
Application #
6878619
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Anderson, James J
Project Start
1991-04-01
Project End
2007-03-31
Budget Start
2005-04-01
Budget End
2006-03-31
Support Year
15
Fiscal Year
2005
Total Cost
$500,866
Indirect Cost
Name
Rockefeller University
Department
Biochemistry
Type
Other Domestic Higher Education
DUNS #
071037113
City
New York
State
NY
Country
United States
Zip Code
10065
Henriques, Rossana; Mas, Paloma (2013) Chromatin remodeling and alternative splicing: pre- and post-transcriptional regulation of the Arabidopsis circadian clock. Semin Cell Dev Biol 24:399-406
Jang, In-Cheol; Henriques, Rossana; Chua, Nam-Hai (2013) Three transcription factors, HFR1, LAF1 and HY5, regulate largely independent signaling pathways downstream of phytochrome A. Plant Cell Physiol 54:907-16
Hemmes, Hans; Henriques, Rossana; Jang, In-Cheol et al. (2012) Circadian clock regulates dynamic chromatin modifications associated with Arabidopsis CCA1/LHY and TOC1 transcriptional rhythms. Plant Cell Physiol 53:2016-29
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Jang, In-Cheol; Chung, Pil Joong; Hemmes, Hans et al. (2011) Rapid and reversible light-mediated chromatin modifications of Arabidopsis phytochrome A locus. Plant Cell 23:459-70
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Wang, Huan; Zhang, Xiuren; Liu, Jun et al. (2011) Deep sequencing of small RNAs specifically associated with Arabidopsis AGO1 and AGO4 uncovers new AGO functions. Plant J 67:292-304
Dong, Li; Liu, Meng; Fang, Yuan-Yuan et al. (2011) DRD1-Pol V-dependent self-silencing of an exogenous silencer restricts the non-cell autonomous silencing of an endogenous target gene. Plant J 68:633-45

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