Research

Exploring the transcriptional landscape of plant circadian rhythms using genome tiling arrays

Samuel P Hazen^1,5 , Felix Naef² , Tom Quisel² , Joshua M Gendron¹ , Huaming Chen³ , Joseph R Ecker³ , Justin O Borevitz⁴ and Steve A Kay¹

¹  Section of Cell and Developmental Biology, University of California San Diego, Gilman Drive, La Jolla, CA 92093-0130, USA

²  School of Life Science, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

³  Plant Biology Laboratory and Genome Analysis Laboratory, The Salk Institute for Biological Studies, N. Torrey Pines Road, La Jolla, CA 92037, USA

⁴  Department of Evolution and Ecology, University of Chicago, E. 57th Street, Chicago, IL 60637, USA

⁵  Biology Department, University of Massachusetts, N. Pleasant Street, Amherst, MA 01003, USA

author email corresponding author email

Genome Biology 2009, 10:R17doi:10.1186/gb-2009-10-2-r17

Published:	11 February 2009

Subject areas: Genome studies, Plant biology

Abstract

Background

Organisms are able to anticipate changes in the daily environment with an internal oscillator know as the circadian clock. Transcription is an important mechanism in maintaining these oscillations. Here we explore, using whole genome tiling arrays, the extent of rhythmic expression patterns genome-wide, with an unbiased analysis of coding and noncoding regions of the Arabidopsis genome.

Results

As in previous studies, we detected a circadian rhythm for approximately 25% of the protein coding genes in the genome. With an unbiased interrogation of the genome, extensive rhythmic introns were detected predominantly in phase with adjacent rhythmic exons, creating a transcript that, if translated, would be expected to produce a truncated protein. In some cases, such as the MYB transcription factor AT2G20400, an intron was found to exhibit a circadian rhythm while the remainder of the transcript was otherwise arrhythmic. In addition to several known noncoding transcripts, including microRNA, trans-acting short interfering RNA, and small nucleolar RNA, greater than one thousand intergenic regions were detected as circadian clock regulated, many of which have no predicted function, either coding or noncoding. Nearly 7% of the protein coding genes produced rhythmic antisense transcripts, often for genes whose sense strand was not similarly rhythmic.

Conclusions

This study revealed widespread circadian clock regulation of the Arabidopsis genome extending well beyond the protein coding transcripts measured to date. This suggests a greater level of structural and temporal dynamics than previously known.