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Genetic Control of Annual Growth Rhythm in the Conifer Norway Spruce (Picea Abies L. Karst)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Norway spruce (Picea abies L. Karst) is a conifer belonging to the group gymnosperms and is an ecologically and economically important species in several parts of Europe. It is crucial for trees like Norway spruce to adapt timing of events such as bud set and growth cessation to the local environment in order to maximize the growth period while avoiding frost damage.

This thesis aims at widening the knowledge about genetic control of annual growth rhythm in Norway spruce and particularly the control of bud set. Using spruce transformants ectopically expressing PaFT/TFL1-LIKE 2 (PaFTL2) the prior hypothesis that PaFTL2 induces bud set is confirmed. This is further supported by spatial and temporal expression patterns in seedlings and adult trees. It is further shown that gymnosperms possess at least two FLOWERING LOCUS T/TERMINAL FLOWER 1 (FT/TFL1)-like genes with TFL1-like function, suggesting the ancestor of FT and TFL1 to be more TFL1-like. PaFTL1 appears to have complementary expression patterns to that of PaFTL2 both spatially and temporally indicating they may act together to control growth in Norway spruce.

Since bud set is controlled by photoperiod and circadian clock genes are implicated in this process, putative clock homologs were studied to gain insight into the circadian clock in gymnosperms. Several clock homologs were identified and their expression showed a diurnal pattern but the expression was rapidly damped in constant conditions. Transgenic Arabidopsis expressing putative core clock genes from spruce indicate that at least three genes, PaCCA1, PaGI and PaZTL, appear to have a conserved function between angiosperms and gymnosperms. Taken together these results suggest that gymnosperms have a similar core clock structure as angiosperms even though fundamental differences might exist since the cycling of the clock genes were rapidly damped in free-running conditions.

The studies presented in this thesis support substantial conservation of pathway components controlling photoperiodic responses in angiosperms and gymnosperms and identify PaFTL2 as a component of growth rhythm control. However, important changes in these processes are also evident. The results provide a solid basis for future research on molecular mechanisms controlling an adaptive trait in an important non-model organism.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 49 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1014
Keyword [en]
bud set, circadian clock, Picea abies, growth cessation, phosphatidyl ethanolamine-binding protein (PEBP) genes
National Category
Plant Biotechnology Biochemistry and Molecular Biology
Research subject
Biology with specialization in Evolutionary Functional Genomics
URN: urn:nbn:se:uu:diva-192180ISBN: 978-91-554-8581-8OAI: oai:DiVA.org:uu-192180DiVA: diva2:589209
Public defence
2013-03-01, Lindahlsalen, EBC, Norbyvägen 18B, Uppsala, 10:00 (English)
Available from: 2013-02-08 Created: 2013-01-16 Last updated: 2013-04-02Bibliographically approved
List of papers
1. Evolution of the PEBP Gene Family in Plants: Functional Diversification in Seed Plant Evolution
Open this publication in new window or tab >>Evolution of the PEBP Gene Family in Plants: Functional Diversification in Seed Plant Evolution
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2011 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 156, no 4, 1967-1977 p.Article in journal (Refereed) Published
Abstract [en]

The phosphatidyl ethanolamine-binding protein (PEBP) gene family is present in all eukaryote kingdoms, with three subfamilies identified in angiosperms (FLOWERING LOCUS T [FT], MOTHER OF FT AND TFL1 [MFT], and TERMINAL FLOWER1 [TFL1] like). In angiosperms, PEBP genes have been shown to function both as promoters and suppressors of flowering and to control plant architecture. In this study, we focus on previously uncharacterized PEBP genes from gymnosperms. Extensive database searches suggest that gymnosperms possess only two types of PEBP genes, MFT-like and a group that occupies an intermediate phylogenetic position between the FT-like and TFL1-like (FT/TFL1-like). Overexpression of Picea abies PEBP genes in Arabidopsis (Arabidopsis thaliana) suggests that the FT/TFL1-like genes (PaFTL1 and PaFTL2) code for proteins with a TFL1-like function. However, PaFTL1 and PaFTL2 also show highly divergent expression patterns. While the expression of PaFTL2 is correlated with annual growth rhythm and mainly confined to needles and vegetative and reproductive buds, the expression of PaFTL1 is largely restricted to microsporophylls of male cones. The P. abies MFT-like genes (PaMFT1 and PaMFT2) show a predominant expression during embryo development, a pattern that is also found for many MFT-like genes from angiosperms. P. abies PEBP gene expression is primarily detected in tissues undergoing physiological changes related to growth arrest and dormancy. A first duplication event resulting in two families of plant PEBP genes (MFT-like and FT/TFL1-like) seems to coincide with the evolution of seed plants, in which independent control of bud and seed dormancy was required, and the second duplication resulting in the FT-like and TFL1-like clades probably coincided with the evolution of angiosperms.

National Category
Natural Sciences
urn:nbn:se:uu:diva-157251 (URN)10.1104/pp.111.176206 (DOI)000293568800025 ()
Available from: 2011-08-25 Created: 2011-08-22 Last updated: 2013-06-27Bibliographically approved
2. FLOWERING LOCUS T/TERMINAL FLOWER1-Like Genes Affect Growth Rhythm and Bud Set in Norway Spruce
Open this publication in new window or tab >>FLOWERING LOCUS T/TERMINAL FLOWER1-Like Genes Affect Growth Rhythm and Bud Set in Norway Spruce
2013 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 163, no 2, 792-803 p.Article in journal (Refereed) Published
Abstract [en]

The timing of bud set, as one determinant of the annual growth rhythm, is critical for local adaptation of the conifer Norway spruce (Picea abies). Previous gene expression and population genetic studies have suggested a role for P. abies FLOWERING LOCUS T/TERMINAL FLOWER1-Like2 (PaFTL2) in the control of growth cessation and bud set in Norway spruce as well as in local adaptation resulting in clinal variation for timing of bud set. Using transgenic plants with PaFTL2 driven by an inducible promoter, we found that PaFTL2 indeed induces bud set and most probably also growth cessation. PaFTL2 shows high expression around the procambium and vascular tissue and in the crown region in buds of both seedlings and older trees. Furthermore, PaFTL2 expression is induced in vegetative shoots and all bud types in late summer, when growth cessation occurs. This supports the notion that PaFTL2 is involved in growth cessation. A close paralog to PaFTL2, PaFTL1, is strongly expressed in meristems during the summer, possibly to repress meristem activity and the formation of needle primordia during this period. The temporal and spatial expression of PaFTL1 and PaFTL2 largely complement each other, which suggests that they act in concert to control perennial growth in Norway spruce.

bud set, Picea abies, transformants, FT/TFL1-like genes, growth cessation
National Category
Biochemistry and Molecular Biology
urn:nbn:se:uu:diva-192123 (URN)10.1104/pp.113.224139 (DOI)000325554100031 ()
Available from: 2013-01-16 Created: 2013-01-16 Last updated: 2014-12-19Bibliographically approved
3. No time for spruce: rapid dampening of circadian rhythms in Picea abies (L. Karst)
Open this publication in new window or tab >>No time for spruce: rapid dampening of circadian rhythms in Picea abies (L. Karst)
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2014 (English)In: Plant and Cell Physiology, ISSN 0032-0781, E-ISSN 1471-9053, Vol. 55, no 3, 535-550 p.Article in journal (Refereed) Published
Picea abies, circadian clock, diurnal cycling, phylogeny, gene expression, delayed fluorescence
National Category
Biochemistry and Molecular Biology
urn:nbn:se:uu:diva-192178 (URN)10.1093/pcp/pct199 (DOI)000333096200007 ()
Available from: 2013-01-16 Created: 2013-01-16 Last updated: 2014-05-05Bibliographically approved
4. Conserved function of core clock proteins in the gymnosperm Norway spruce (Picea abies L. Karst)
Open this publication in new window or tab >>Conserved function of core clock proteins in the gymnosperm Norway spruce (Picea abies L. Karst)
2013 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 8, no 3, e60110- p.Article in journal (Refereed) Published
Abstract [en]

From studies of the circadian clock in the plant model species Arabidopsis (Arabidopsis thaliana), a number of important properties and components have emerged. These include the genes CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), GIGANTEA (GI), ZEITLUPE (ZTL) and TIMING OF CAB EXPRESSION 1 (TOC1 also known as PSEUDO-RESPONSE REGULATOR 1 (PRR1)) that via gene expression feedback loops participate in the circadian clock. Here, we present results from ectopic expression of four Norway spruce (Picea abies) putative homologs (PaCCA1, PaGI, PaZTL and PaPRR1) in Arabidopsis, their flowering time, circadian period length, red light response phenotypes and their effect on endogenous clock genes were assessed. For PaCCA1-ox and PaZTL-ox the results were consistent with Arabidopsis lines overexpressing the corresponding Arabidopsis genes. For PaGI consistent results were obtained when expressed in the gi2 mutant, while PaGI and PaPRR1 expressed in wild type did not display the expected phenotypes. These results suggest that protein function of PaCCA1, PaGI and PaZTL are at least partlyconserved compared to Arabidopsis homologs, however further studies are needed to reveal the protein function of PaPRR1. Our data suggest that components of thethree-loop network typical of the circadian clock in angiosperms were present beforethe split of gymnosperms and angiosperms.

circadian clock, Picea abies (Norway spruce), transformants, gymnosperm, ZEITLUPE (ZTL), GIGANTEA (GI), TIMING OF CAB1 (TOC1 or PRR1), CIRCADIAN CLOCK ASSOCIATED 1 (CCA1)
National Category
Biochemistry and Molecular Biology
urn:nbn:se:uu:diva-192151 (URN)10.1371/journal.pone.0060110 (DOI)000317262200084 ()
Available from: 2013-01-16 Created: 2013-01-16 Last updated: 2013-05-22Bibliographically approved

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