University of Illinois Urbana-Champaign

Circadian regulation and phytohormone responses of cytochrome P450 monooxygenase genes in Arabidopsis

Pan, Yinghong

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Yinghong_Pan.pdf

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https://hdl.handle.net/2142/42197

Description

Title
Circadian regulation and phytohormone responses of cytochrome P450 monooxygenase genes in Arabidopsis
Author(s)
Pan, Yinghong
Issue Date
2013-02-03T19:27:36Z
Director of Research (if dissertation) or Advisor (if thesis)
Schuler, Mary A.
Doctoral Committee Chair(s)
Schuler, Mary A.
Committee Member(s)
  • Zielinski, Raymond E.
  • Ming, Ray R.
  • Clough, Steven J.
Department of Study
School of Integrative Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Date of Ingest
2013-02-03T19:27:36Z
Keyword(s)
  • Arabidopsis
  • cytochrome P450s
  • circadian
  • phytohormones
Abstract
Plant growth and development are regulated by both hormone and circadian signaling pathways. The growing number of signaling molecules whose syntheses are circadian-regulated (e.g. jasmonic acid, auxin) and the time-of-day-specific transcripts of cytochrome P450 monooxygenases (P450s) involved in their syntheses and catabolisms suggest an interactions between hormone signaling network and circadian signaling network. The first phase of my research profiled a total of 98 P450 genes in Arabidopsis thaliana as circadian-regulated at a transcriptional level under varying photoperiod and thermocycle conditions, and demonstrated that P450s involved in phenylpropanoid, carotenoid, oxylipin, glucosinolate and brassinosteroid biosynthese pathways are circadian-regulated. The next phase of my research investigated the circadian rhythms of P450 genes under different phytohormone treatments including methyl jasmonate (MeJ), salicylic acid (SA), abscisic acid (ABA) and indole-3-acetic acid (IAA). My analysis of transcript profiles of seedlings treated with individual hormones indicated the responses of many P450 genes to these hormone treatments are gated by circadian clock. And different hormone inductions also provided feedback to the circadian clock of P450 gene expressions by affecting their phase, amplitude, period and precision. In silico cis-element analyses of co-regulated promoters in different pathways identified that many known elements including Evening Element, CCA1 Binding Site and G-Box variant elements, as well as some novel elements including JA1 and TRP1 were over-represented and likely to be important in circadian regulation and/or hormone induction. The third phase of my research focused on the bHLH transcription factor MYC2, which plays a critical role in JA signaling and its crosstalk with many other stresses. Analysis of myc2 knockout plants confirmed that MYC2 positively regulated the JA pathway and negatively regulated the IG pathway, and that the MeJ responses of JA signaling genes were only moderately reduced in the mutant seedlings. The work suggests that there are transcription factors other than MYC2 playing a major role in regulating the responses to MeJ. Three closely related genes MYC3, MYC4 and MYC5 were found to bind to the same DNA binding sites as MYC2, which might play different roles, in concert with MYC2 in the integration of JA-signaling to control both circadian and hormone response processes.
Graduation Semester
2012-12
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http://hdl.handle.net/2142/42197
Copyright and License Information
Copyright 2012 Yinghong Pan

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