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The Circadian Clock in Annuals and Perennials Coordination of Growth with Environmental Rhythms

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The Circadian Clock in Annuals and Perennials Coordination of Growth with Environmental Rhythms The Circadian Clock in Annuals and Perennials Coordination of Growth with Environmental Rhythms Mikael Johansson Akademisk avhandling som med vederbörligt tillstånd av Rektorsämbetet vid Umeå universitet för avläggande av filosofie doktorsexamen i Växters cell- och molekylärbiologi framläggs till offentligt försvar i KB3B1, KBC-huset, Umeå universitet, fredagen den 1 Oktober kl. 10:00. Avhandlingen kommer att försvaras på engelska. Fakultetsopponent: Dr. Paul Devlin, Royal Holloway University of London, United Kingdom Umeå Plant Science Centre Department of Plant Physiology, Umeå University, Umeå, Sweden 2010 The Circadian Clock in Annuals and Perennials: Coordination of Growth with Environmental Rhythms Mikael Johansson Umeå Plant Science Centre, Department of Plant Physiology, Umeå University ISBN: 978-91- 7459-062-3 Abstract Since the first signs of life on planet earth, organisms have had to adapt to the daily changes between light and dark, and high and low temperatures. This has led to the evolution of an endogenous time keeper, known as the circadian clock. This biological timing system helps the organism to synchronize developmental and metabolic events to the most favorable time of the day. Such a mechanism is of considerable value to plants, since they in contrast to animals cannot change location when the environment becomes unfavorable. Thus is the ability to predict coming events of central importance in a plants life. This thesis is a study of the molecular machinery behind the clockwork in the small weed plant Arabidopsis thaliana as well as its close relative perennial; the woody species Populus. We have characterized a novel component of the circadian clock, EARLY BIRD (EBI). EBI is involved in transcriptional and translational regulation, via interaction with the known post-translational clock regulator ZEITLUPE (ZTL). In Populus, we describe the role of the circadian clock and its components with respect to entry and exit of dormancy and show that gene expression of the Populus LATE ELONATED HYPOCOTYL (LHY) genes are crucial importance for freezing tolerance and thereby survival at high latitudes. Furthermore, the input to the Populus clock is mediated via the phytochrome A (phyA) photoreceptor. Keywords: Arabidopsis, Populus, Circadian Clock The Circadian Clock in Annuals and Perennials Coordination of Growth with Environmental Rhythms Mikael Johansson Umeå Plant Science Centre Department of Plant Physiology, Umeå University, Umeå, Sweden 2010 © Mikael Johansson, 2010 Detta verk skyddas enligt lagen om upphovsrätt (URL 1960:729) ISBN: 978-91- 7459-062-3 Cover: Arabidopsis seedlings expressing CAB:LUC over 24 hours Electronic version available at http://umu.diva-portal.org/ Printed by: Arkitektkopia, Umeå, Sweden 2010 ii Till min kära mor iii Abstract Since the first signs of life on planet earth, organisms have had to adapt to the daily changes between light and dark, and high and low temperatures. This has led to the evolution of an endogenous time keeper, known as the circadian clock. This biological timing system helps the organism to synchronize developmental and metabolic events to the most favorable time of the day. Such a mechanism is of considerable value to plants, since they in contrast to animals cannot change location when the environment becomes unfavorable. Thus is the ability to predict coming events of central importance in a plants life. This thesis is a study of the molecular machinery behind the clockwork in the small weed plant Arabidopsis thaliana as well as its close relative perennial; the woody species Populus. We have characterized a novel component of the circadian clock, EARLY BIRD (EBI). EBI is involved in transcriptional and translational regulation, via interaction with the known post-translational clock regulator ZEITLUPE (ZTL). In Populus, we describe the role of the circadian clock and its components with respect to entry and exit of dormancy and show that gene expression of the Populus LATE ELONATED HYPOCOTYL (LHY) genes are crucial importance for freezing tolerance and thereby survival at high latitudes. Furthermore, the input to the Populus clock is mediated via the phytochrome A (phyA) photoreceptor. Keywords: Arabidopsis, Populus, Circadian Clock iv Sammanfattning Liv på jorden har alltid behövt anpassa sig till de dagliga växlingarna mellan främst ljus och mörker. Detta har lett till evolutionen av en intern, biologisk klocka, känd som den circadianska klockan, efter latinets ”circa diem”, som betyder ”ungefär en dag”. Denna inre klocka hjälper organismer att styra biologiska processer till den tid på dygnet som är mest gynnsam för deras utveckling och överlevnad. Denna mekanism är av stort värde för växter, eftersom de inte kan söka skydd på mera lämpliga platser om de blir utsatta för olika former av stress. Det gör att förmågan att förutse kommande händelser är av yttersta vikt för växter. Denna avhandling är en studie av det molekylära nätverk som styr denna biologiska klocka i den lilla örtplantan Arabidopsis thaliana (backtrav), och den besläktade träd-arten Populus (hybrid- asp). Vi har karaktäriserat en ny komponent i den circadianska klockan i Arabidopsis, EARLY BIRD (EBI). EBI är involverad i transkriptionell och translationell reglering av klockan, via interaktion med den kända post- translationella klock-regulatorn ZEITLUPE (ZTL). I Populus har vi beskrivit den interna klockan och dess roll i processer som invintring, vinterdvala och återstart av tillväxt. LATE ELONATED HYPOCOTYL (LHY) generna i Populus är avgörande för förvärv av köld-tolerans och således överlevnad på högre latituder. Dessutom har vi visat att signaler till den circadianska klockan i Populus är medierade via fotoreceptorn phytochrome A (phyA). v Abbreviations All abbreviations are explained when they first appear in the text. vi List of Papers This thesis is based on the following publications, which will be referred to in the text by their Roman numerals (I-V). I Mikael Johansson*, Harriet G. McWatters*, László Bakó, Naoki Takata, Péter Gyula, Anthony Hall, David E. Somers, Andrew J. Millar and Maria E. Eriksson. Partners in time: EARLY BIRD reveals novel regulatory function of ZEITLUPE in the Arabidopsis clock Manuscript II Kevin Ashelford*, Maria. E. Eriksson*, Christopher M Allen, Linda D’Amore, Mikael Johansson, Peter Gould , Susanne Kay, Andrew J. Millar, Neil Hall and Anthony Hall. Full genome re-sequencing reveals a novel circadian clock mutation in Arabidopsis Manuscript III Mikael Johansson, Iwanka Kozarewa and Maria E. Eriksson ZEITLUPE promoter activity is modulated in an EARLY BIRD dependent manner in response to abscisic acid Manuscript IV Cristian Ibáñez*, Iwanka Kozarewa*, Mikael Johansson*, Erling Ögren, Antje Rohde, and Maria E. Eriksson. Circadian Clock Components Regulate Entry and Affect Exit of Seasonal Dormancy as Well as Winter Hardiness in Populus Trees Plant Physiology (2010) 153:1823–1833 V Iwanka Kozarewa*, Cristian Ibáñez*, Mikael Johansson, Erling Ögren, David Mozley, Eva Nylander, Makiko Chono, Thomas Moritz and Maria E. Eriksson. Alteration of PHYA expression change circadian rhythms and timing of bud set in Populus. Plant Mol Biol (2010) 73:143–156 *These authors contributed equally to respective manuscript Paper IV is published with the kind permission of the American Society of Plant Biologists. Paper V is published with the kind permission of Springer/Kluwer Academic Publishers. vii Clock linguistics Annual and perennial plants – Annual plants complete their life cycle over one season, while perennial plants lives for three or more seasons. Bud burst – Breaking of buds, growth resumption following, for example, winter dormancy Bud set/formation – The process following cessation of elongation growth when the apical meristem is enclosed by bud scales Circadian, Circannual – A circadian rhythm repeats itself daily, a circannual rhythm repeats yearly. Critical day length – The length of photoperiod/darkness required to trigger a photoperiodic response, for instance dormancy or flowering. Diurnal, nocturnal – Diurnal organisms are active during the day, nocturnal during the night. Dormancy – The inability to initiate growth from meristems under favourable conditions. A state during the winter season in woody species such as Populus, when no visible growth occurs. Entrainment – The process that sets the pace of a circadian rhythm with an external cue. Free-running – A rhythm that is not affected by any zeitgebers and thus runs freely. Growth cessation – Inhibition of internode elongation or cambial growth Input, output – Input is a signal that goes to the clock and then, depending on (for example) time of day, will result in an output, e.g. a physiological response. Long/short day plants – Plants that require a short/longer period of darkness to flower Masked rhythms – rhythms that are hidden by other non-circadian events that happen to have the same pattern. Oscillator – The core clock genes keeping track of time are often collectively referred to as a biological oscillator Period, Phase, Amplitude – Nomenclature to describe a rhythm; see ‘Expression of Clock Genes’. Rhythm - The repetitive pattern of for example gene expression. Zeitgeber – All signals that have the ability to entrain the endogenous clock. viii Table of Contents Abstract…………………………………………………………………iv Sammanfattning………………………………………………………...v Abbreviations…………………………………………………………...vi List of Papers…………………………………………………………..vii Clock Linguistics……………………………………………………..viii Preface.................................................................................
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