Natural diversity in daily rhythms of gene expression contributes to phenotypic variation

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-01, Vol.112 (3), p.905-910
• Main Authors: de Montaigu, Amaury, Giakountis, Antonis, Rubin, Matthew, Tóth, Réka, Cremer, Frédéric, Sokolova, Vladislava, Porri, Aimone, Reymond, Matthieu, Weinig, Cynthia, Coupland, George
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - physiology; Biological Sciences; Circadian Rhythm; Gene expression; Gene Expression Regulation, Plant; Genotype & phenotype; Light; Sensitivity analysis; Signal Transduction
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1422242112

Daily rhythms of gene expression provide a benefit to most organisms by ensuring that biological processes are activated at the optimal time of day. Although temporal patterns of expression control plant traits of agricultural importance, how natural genetic variation modifies these patterns during the day and how precisely these patterns influence phenotypes is poorly understood. The circadian clock regulates the timing of gene expression, and natural variation in circadian rhythms has been described, but circadian rhythms are measured in artificial continuous conditions that do not reflect the complexity of biologically relevant day/night cycles. By studying transcriptional rhythms of the evening-expressed gene GIGANTEA ( GI ) at high temporal resolution and during day/night cycles, we show that natural variation in the timing of GI expression occurs mostly under long days in 77 Arabidopsis accessions. This variation is explained by natural alleles that alter light sensitivity of GI , specifically in the evening, and that act at least partly independent of circadian rhythms. Natural alleles induce precise changes in the temporal waveform of GI expression, and these changes have detectable effects on PHYTOCHROME INTERACTING FACTOR 4 expression and growth. Our findings provide a paradigm for how natural alleles act within day/night cycles to precisely modify temporal gene expression waveforms and cause phenotypic diversity. Such alleles could confer an advantage by adjusting the activity of temporally regulated processes without severely disrupting the circadian system. Significance Daily rhythms of gene expression ensure that biological processes occur at the optimal time of day. In plants, temporally regulated processes include traits of ecological and agricultural importance, and understanding how changes in daily rhythms of expression modify such traits has broad implications. We find that natural genetic variation can accurately modify temporal gene expression waveforms during the day by influencing light signaling pathways, rather than circadian rhythms. We further show that changes in transcriptional patterns induced by natural alleles are sufficient to affect downstream molecular outputs and cause phenotypic diversity. Such natural alleles could provide an advantage by adjusting the activity of temporally regulated processes while avoiding the pleiotropic effects associated with severe disruptions of the circadian system.