Identification and characterization of circadian clock genes in a native tobacco, Nicotiana attenuata

Felipe Yon,Pil-Joon Seo,Jae Yong Ryu,Ian T Baldwin,Sang-Gyu Kim,Chung-Mo Park

doi:10.1186/1471-2229-12-172

Abstract

BackgroundA plant’s endogenous clock (circadian clock) entrains physiological processes to light/dark and temperature cycles. Forward and reverse genetic approaches in Arabidopsis have revealed the mechanisms of the circadian clock and its components in the genome. Similar approaches have been used to characterize conserved clock elements in several plant species. A wild tobacco, Nicotiana attenuata has been studied extensively to understand responses to biotic or abiotic stress in the glasshouse and also in their native habitat. During two decades of field experiment, we observed several diurnal rhythmic traits of N. attenuata in nature. To expand our knowledge of circadian clock function into the entrainment of traits important for ecological processes, we here report three core clock components in N. attenuata.ResultsProtein similarity and transcript accumulation allowed us to isolate orthologous genes of the core circadian clock components, LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION 1/PSEUDO-RESPONSE REGULATOR 1 (TOC1/PRR1), and ZEITLUPE (ZTL). Transcript accumulation of NaLHY peaked at dawn and NaTOC1 peaked at dusk in plants grown under long day conditions. Ectopic expression of NaLHY and NaZTL in Arabidopsis resulted in elongated hypocotyl and late-flowering phenotypes. Protein interactions between NaTOC1 and NaZTL were confirmed by yeast two-hybrid assays. Finally, when NaTOC1 was silenced in N. attenuata, late-flowering phenotypes under long day conditions were clearly observed.ConclusionsWe identified three core circadian clock genes in N. attenuata and demonstrated the functional and biochemical conservation of NaLHY, NaTOC1, and NaZTL.

Highlights

IntroductionA plant’s endogenous clock (circadian clock) entrains physiological processes to light/dark and temperature cycles
A plant’s endogenous clock entrains physiological processes to light/dark and temperature cycles
In order to expand our understanding of the clock function in biotic and abiotic interactions, we identified three core clock components (LHY, TOC1, and ZTL) in a wild tobacco, Nicotiana attenuata, which has been developed as a model system for understanding ecological performance in native habitats, in particular the Great Basin desert in Utah

Summary

Introduction

A plant’s endogenous clock (circadian clock) entrains physiological processes to light/dark and temperature cycles. To expand our knowledge of circadian clock function into the entrainment of traits important for ecological processes, we here report three core clock components in N. attenuata. The endogenous clock in plants influences various biological processes including leaf movements, hypocotyl growth, floral transition, and abiotic and biotic stress resistance [2,3,4]. Several interconnected transcription/ translation feedback loops participate to establish central clock oscillations [8,9,10]. TIMING OF CAB EXPRESSION 1/PSEUDO-RESPONSE REGULATOR 1 (TOC1/PRR1) and two partially redundant MYB transcription factors, CIRCADIAN CLOCKASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) comprise a central oscillation loop [12]. The third loop is established by negative feedback between PRR7/PRR9 and LHY/CCA1 [16,17]

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