Organisms that fail to respond appropriately to seasonal change will face severe consequences related to survival and reproduction. For humans, seasonal variation in the amount of light causes Seasonal Affective Disorder (SAD), a recurrent subtype of depression. Although the molecular mechanisms underlying SAD remain elusive, it is known that photoperiodic mechanisms play a significant role in many cases of SAD. Many organisms, including humans, have evolved mechanisms to sense changes in day length (=photoperiod) and integrate seasonal change information into their development. The long-term goal of our research program is to elucidate the molecular mechanisms by which organisms measure changes in day length and adjust their behaviors and development accordingly. Although the molecular mechanisms of photoperiodism have not yet been well described in many organisms, recent advances in the study of the model plant Arabidopsis have increased our molecular understanding of photoperiodic time measurement and have influenced the study of other plant and animal species. In Arabidopsis, the core time-measurement mechanism is circadian-regulated transcription of the floral activator CONSTANS (CO) gene and light-regulated CO protein stability and activity. In this proposal, further characterization o this core mechanism will be done through biochemical, genetic, and genomic approaches.
In Aim 1, newly identified transcriptional regulators of CO will be characterized. The findings will elucidate further how the circadian clock plays a role in regulating seasonal response by orchestrating different classes of transcription factors.
In Aim 2, time-dependent chromatin modification of CO transcriptional regulation - a new mechanistic layer of understanding - will be studied. Our previous results indicated the involvement of the FKF1 blue-light photoreceptor in posttranslational regulation of CO protein.
In Aim 3, the molecular function of FKF1-associating proteins on CO protein stability regulation will be examined. With these three Aims, the mechanisms by which plants monitor daily and seasonal differences through the circadian clock will be analyzed. The findings will impact plant research and our broader understanding of photoperiodism and circadian clocks in mammals and other systems. The types of transcriptional and posttranslational mechanisms present in Arabidopsis are likely conserved among all eukaryotes, thus these findings will contribute to our understanding of fundamental transcriptional regulation. These findings also have the potential to provide clues to the mechanisms involved in SAD. Finally, elucidating the photoperiodic flowering mechanism is important for understanding a major plant reproduction mechanism that is directly applicable to improvements in crop yield, an important contributor to human health especially in developing countries.

Public Health Relevance

Failure to adapt to seasonal change can have critical impacts on an organism's survival and reproductive success, and on human behavior. This proposed research, regarding the molecular mechanisms of day-length measurement in plants, will be important for plant research and for a broader understanding of photoperiodism and circadian clock-regulated behaviors in mammals and other organisms. In addition, elucidating this mechanism is essential for understanding a major plant reproduction mechanism, one that is directly applicable for improvement of crop yield (an important contributor to human health, especially in developing countries) and to our understanding of a sophisticated, time-resolved transcriptional mechanism that is universal and fundamental among all eukaryotes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM079712-08
Application #
8503273
Study Section
Molecular Genetics B Study Section (MGB)
Program Officer
Sesma, Michael A
Project Start
2007-04-01
Project End
2017-03-31
Budget Start
2013-07-01
Budget End
2014-03-31
Support Year
8
Fiscal Year
2013
Total Cost
$285,975
Indirect Cost
$95,975
Name
University of Washington
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
Li, Shibai; Wang, Xiaochen; He, Shan et al. (2016) CFLAP1 and CFLAP2 Are Two bHLH Transcription Factors Participating in Synergistic Regulation of AtCFL1-Mediated Cuticle Development in Arabidopsis. PLoS Genet 12:e1005744
Fenske, Myles P; Imaizumi, Takato (2016) Circadian Rhythms in Floral Scent Emission. Front Plant Sci 7:462
Kinmonth-Schultz, Hannah A; Tong, Xinran; Lee, Jae et al. (2016) Cool night-time temperatures induce the expression of CONSTANS and FLOWERING LOCUS T to regulate flowering in Arabidopsis. New Phytol 211:208-24
Fenske, Myles P; Hewett Hazelton, Kristen D; Hempton, Andrew K et al. (2015) Circadian clock gene LATE ELONGATED HYPOCOTYL directly regulates the timing of floral scent emission in Petunia. Proc Natl Acad Sci U S A 112:9775-80
Shim, Jae Sung; Imaizumi, Takato (2015) Circadian clock and photoperiodic response in Arabidopsis: from seasonal flowering to redox homeostasis. Biochemistry 54:157-70
Kubota, Akane; Shim, Jae Sung; Imaizumi, Takato (2015) Natural variation in transcriptional rhythms modulates photoperiodic responses. Trends Plant Sci 20:259-61
Song, Young Hun; Shim, Jae Sung; Kinmonth-Schultz, Hannah A et al. (2015) Photoperiodic flowering: time measurement mechanisms in leaves. Annu Rev Plant Biol 66:441-64
Seaton, Daniel D; Smith, Robert W; Song, Young Hun et al. (2015) Linked circadian outputs control elongation growth and flowering in response to photoperiod and temperature. Mol Syst Biol 11:776
Golembeski, Greg S; Imaizumi, Takato (2015) Photoperiodic Regulation of Florigen Function in Arabidopsis thaliana. Arabidopsis Book 13:e0178
Golembeski, Greg S; Kinmonth-Schultz, Hannah A; Song, Young Hun et al. (2014) Photoperiodic flowering regulation in Arabidopsis thaliana. Adv Bot Res 72:1-28

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