| 1. |
- Jurca, Manuela, et al.
(författare)
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ZEITLUPE Promotes ABA-Induced Stomatal Closure in Arabidopsis and Populus
- 2022
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Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Plants balance water availability with gas exchange and photosynthesis by controlling stomatal aperture. This control is regulated in part by the circadian clock, but it remains unclear how signalling pathways of daily rhythms are integrated into stress responses. The serine/threonine protein kinase OPEN STOMATA 1 (OST1) contributes to the regulation of stomatal closure via activation of S-type anion channels. OST1 also mediates gene regulation in response to ABA/drought stress. We show that ZEITLUPE (ZTL), a blue light photoreceptor and clock component, also regulates ABA-induced stomatal closure in Arabidopsis thaliana, establishing a link between clock and ABA-signalling pathways. ZTL sustains expression of OST1 and ABA-signalling genes. Stomatal closure in response to ABA is reduced in ztl mutants, which maintain wider stomatal apertures and show higher rates of gas exchange and water loss than wild-type plants. Detached rosette leaf assays revealed a stronger water loss phenotype in ztl-3, ost1-3 double mutants, indicating that ZTL and OST1 contributed synergistically to the control of stomatal aperture. Experimental studies of Populus sp., revealed that ZTL regulated the circadian clock and stomata, indicating ZTL function was similar in these trees and Arabidopsis. PSEUDO-RESPONSE REGULATOR 5 (PRR5), a known target of ZTL, affects ABA-induced responses, including stomatal regulation. Like ZTL, PRR5 interacted physically with OST1 and contributed to the integration of ABA responses with circadian clock signalling. This suggests a novel mechanism whereby the PRR proteins—which are expressed from dawn to dusk—interact with OST1 to mediate ABA-dependent plant responses to reduce water loss in time of stress.
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| 2. |
- Ding, Jihua, et al.
(författare)
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GIGANTEA-like genes control seasonal growth cessation in Populus
- 2018
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 218:4, s. 1491-1503
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Tidskriftsartikel (refereegranskat)abstract
- Survival of trees growing in temperate zones requires cycling between active growth and dormancy. This involves growth cessation in the autumn triggered by a photoperiod shorter than the critical day length. Variations in GIGANTEA (GI)-like genes have been associated with phenology in a range of different tree species, but characterization of the functions of these genes in the process is still lacking. We describe the identification of the Populus orthologs of GI and their critical role in short-day-induced growth cessation. Using ectopic expression and silencing, gene expression analysis, protein interaction and chromatin immunoprecipitation experiments, we show that PttGIs are likely to act in a complex with PttFKF1s (FLAVIN-BINDING, KELCH REPEAT, F-BOX 1) and PttCDFs (CYCLING DOF FACTOR) to control the expression of PttFT2, the key gene regulating short-day-induced growth cessation in Populus. In contrast to Arabidopsis, in which the GI-CONSTANS (CO)-FLOWERING LOCUS T (FT) regulon is a crucial day-length sensor for flowering time, our study suggests that, in Populus, PttCO-independent regulation of PttFT2 by PttGI is more important in the photoperiodic control of growth cessation and bud set.
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| 3. |
- Johansson, Mikael, et al.
(författare)
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Monitoring seasonal bud set, bud burst, and cold hardiness in populus
- 2022
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Ingår i: Plant circadian networks. - New York, NY : Humana Press. - 9781071619117 - 9781071619124 ; , s. 215-226
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Bokkapitel (refereegranskat)abstract
- Using a perennial model plant allows the study of reoccurring seasonal events in a way that is not possible using a fast-growing annual such as A. thaliana (Arabidopsis). In this study, we present a hybrid aspen (Populus tremula × P. tremuloides) as our perennial model plant. These plants can be grown in growth chambers to shorten growth periods and manipulate day length and temperature in ways that would be impossible under natural conditions. In addition, the use of growth chambers allows easy monitoring of height and diameter expansion, accelerating the collection of data from new strategies that allow evaluation of promoters or inhibitors of growth. Here, we describe how to study and quantify responses to seasonal changes (mainly using P. tremula × P. tremuloides) by measuring growth rate and key events under different photoperiodic cycles.
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| 4. |
- Johansson, Mikael, et al.
(författare)
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The perennial clock is an essential timer for seasonal growth events and cold hardiness
- 2022
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Ingår i: Plant circadian networks. - New York, NY : Humana Press. - 9781071619117 - 9781071619124 ; , s. 227-242
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Bokkapitel (refereegranskat)abstract
- Over the last several decades, changes in global temperatures have led to changes in local environments affecting the growth conditions for many species. This is a trend that makes it even more important to understand how plants respond to local variations and seasonal changes in climate. To detect daily and seasonal changes as well as acute stress factors such as cold and drought, plants rely on a circadian clock. This chapter introduces the current knowledge and literature about the setup and function of the circadian clock in various tree and perennial species, with a focus on the Populus genus.
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| 5. |
- Jurca, Manuela, et al.
(författare)
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Biotechnological adaptation of seasonal growth using high yielding Populus gibberellin overproducing trees
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Tree growth is central to terrestrial ecology and the forestry industry. The overproduction by biotechnological means of hormones such as gibberellins (GAs) has been used as a powerful toolto greatly increase tree yield and wood properties. However, for trees in temperate and boreal regions, overexpressing GAs prevents the ability to induce vegetative dormancy, and results in reduced yield and tree loss over time. Since Populus trees are using an internal 24-h (circadian) clock to synchronize their metabolism and growth with local, predictable changes in the external environment, we focused on circadian control of GA metabolism, to showcase the principle of seasonal growth adaptation. To obtain both maintained growth benefits and a seasonally timed growth, we set out to modulate levels of bioactive GAs by using the endogenous Populus tremula× P. tremuloides CycD3 promoter. We show that both high yield and biotechnical seasonal growth adaptation is obtained with this promoter, which is coordinated by the clock protein LATE ELONGATED HYPOCOTYL 2 (PttLHY2). This work paves the way for future precision breeding of trees with local adaptation and increased yield.
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| 6. |
- McWatters, Harriet G
(författare)
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Plant Circadian Rhythms
- 2016
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Ingår i: Encyclopedia of Life Sciences. - Chichester : John Wiley & Sons. ; , s. 1-10
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Bokkapitel (refereegranskat)abstract
- Circadian clocks are found in most eukaryotic organisms. By allowing anticipation of daily and seasonal changes, they enable coordination of metabolism and lifecycle with the natural rhythms of the environment. Plant circadian rhythms are generated by a series of interlocking feedback loops of RNA (ribonucleic acid) and protein expression that respond to environmental cycles of light and temperature. They control essential processes in the plant's development, such as the transition to flowering or growth cessation, and thus influence yield, plant growth and biomass production. Many components of the clock are conserved across a wide variety of plant species and thus research in Arabidopsis translates into an understanding of the clock in agricultural crops or long‐living deciduous tree species such as hybrid aspen.Key ConceptsCircadian clocks are found in both eukaryotes and bacteria.Circadian clocks have a free‐running periodicity of about 24 h but are normally entrained to environmental cycles of light and temperature.Temperature compensation is a key feature of the circadian clock and thus the free‐running period length varies relatively little across the range of ambient temperature.The clock underlies many aspects of plant metabolism and physiology because it can detect and respond to both short‐term (the day:night cycle) and long‐term (the pattern of daylength variation across a year) changes in light and temperature.The circadian clock of plants is made up of a series of interconnected transcription‐translation feedback loops (TTFLs) governing cycles of mRNA and protein expression.Every plant cell contains its own clock. Clocks in different cells may be entrained independently of one another, although there appears to be a hierarchy of clocks within a plant dominated by the apex.Plants with malfunctioning clocks suffer reductions in growth.Many of the key components of the plant clock first described in the model species Arabidopsis thaliana are conserved across a wide range of species including trees such as hybrid aspen.
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| 7. |
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Role of the Circadian Clock in Cold Acclimation and Winter Dormancy in Perennial Plants
- 2015
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- Seasonal variation is a strong cue directing the growth and development of plants. It is particularly important for perennials growing in temperate and boreal regions where woody plants must become dormant to survive freezing winter temperatures. Shortening of the photoperiod induces growth cessation, bud set and a first degree of cold acclimation in most woody plants. The subsequent drop in temperature then produces a greater tolerance to cold and, in deciduous trees, leaf senescence and fall. Trees must time their periods of dormancy accurately with their environment. Circadian clocks underlie this ability, allowing organisms to predict regular, daily changes in their environment as well as longer term seasonal changes. This chapter provides an update on the plant clock in a model annual, thale cress (Arabidopsis thaliana), and further summarizes recent advances about the clock in perennial plants and its involvement in their annual growth cycles, which allows trees to withstand cold and freezing temperatures. Moreover, we outline our views on areas where future work on the circadian clock is necessary to gain insight into the life of a tree.
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| 8. |
- Singh, Rajesh Kumar, et al.
(författare)
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Growing in time : exploring the molecular mechanisms of tree growth
- 2021
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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 41:4, s. 657-678
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Forskningsöversikt (refereegranskat)abstract
- Trees cover vast areas of the Earth's landmasses. They mitigate erosion, capture carbon dioxide, produce oxygen and support biodiversity, and also are a source of food, raw materials and energy for human populations. Understanding the growth cycles of trees is fundamental for many areas of research. Trees, like most other organisms, have evolved a circadian clock to synchronize their growth and development with the daily and seasonal cycles of the environment. These regular changes in light, daylength and temperature are perceived via a range of dedicated receptors and cause resetting of the circadian clock to local time. This allows anticipation of daily and seasonal fluctuations and enables trees to co-ordinate their metabolism and physiology to ensure vital processes occur at the optimal times. In this review, we explore the current state of knowledge concerning the regulation of growth and seasonal dormancy in trees, using information drawn from model systems such as Populus spp.
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| 9. |
- Sjölander, Johan, et al.
(författare)
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Circadian clock components control growth and gibberellin metabolism in Populus trees
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This study investigates the role of the circadian clock in the regulation of gibberellin (GA) metabolism and growth in hybrid aspen (Populus tremula x P. tremuloides (Ptt)). We revealed a conserved function of the clock homolog PttEARLY BIRD1 (PttEBI1), but also implicated its rolein controlling tree growth. GA metabolite profiling and transcriptomic analysis in hybrid aspenlines with modulated expression of PttEBI1 or the core clock homologs PttLATE ELONGATED HYPOCOTYLs (PttLHYs) revealed significant changes in GA metabolism. These alterations werelinked to the differential expression of PttGA2ox8, a gene encoding an enzyme with both GA2-oxidase and GA20-oxidase activities. Our results indicate that modifications to circadian clockcomponents can significantly influence both GA metabolism and tree growth, providing potential strategies for improving tree biomass production.
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