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1.
Physiol Plant ; 175(4): e13953, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37318218

RESUMO

The ability to tolerate low freezing temperatures is an important component of winter survival and persistence of red clover. Cold acclimation (CA) allows plants to acquire higher levels of freezing tolerance. However, the biochemical responses to cold and the importance of such changes for the plant to acquire adequate freezing tolerance have not been investigated in red clover of Nordic origin, which has a distinct genetic background. To shed light on this, we selected five freezing tolerant (FT) and five freezing susceptible (FS) accessions and studied the effect of CA on the contents of carbohydrates, amino acids, and phenolic compounds in the crowns. Among those compounds which increased during CA, FT accessions had higher contents of raffinose, pinitol, arginine, serine, alanine, valine, phenylalanine, and one phenolic compound (a pinocembrin hexoside derivative) than FS accessions, suggesting a role for these compounds in the freezing tolerance in the selected accessions. These findings, together with a description of the phenolic profile of red clover crowns, significantly add to the current knowledge of the biochemical changes during CA and their role in freezing tolerance in Nordic red clover.


Assuntos
Trifolium , Congelamento , Trifolium/genética , Temperatura Baixa , Carboidratos , Aclimatação/fisiologia
2.
J Exp Bot ; 73(11): 3807-3822, 2022 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-35298622

RESUMO

De-methyl esterification of homogalacturonan and subsequent cross-linking with Ca2+ is hypothesized to enhance the freezing survival of cold acclimated plants by reducing the porosity of primary cell walls. To test this theory, we collected leaf epidermal peels from non- (23/18 °C) and cold acclimated (2 weeks at 12/4 °C) Japanese bunching onion (Allium fistulosum L.). Cold acclimation enhanced the temperature at which half the cells survived freezing injury by 8 °C (LT50 =-20 °C), and reduced tissue permeability by 70-fold compared with non-acclimated epidermal cells. These effects were associated with greater activity of pectin methylesterase (PME) and a reduction in the methyl esterification of homogalacturonan. Non-acclimated plants treated with 50 mM CaCl2 accumulated higher concentrations of galacturonic acid, Ca2+ in the cell wall, and a lower number of visible cell wall pores compared with that observed in cold acclimated plants. Using cryo-microscopy, we observed that 50 mM CaCl2 treatment did not lower the LT50 of non-acclimated cells, but reduced the lethal intracellular ice nucleation to temperatures observed in cold acclimated epidermal cells. We postulate that the PME-homogalacturonan-mediated reduction in cell wall porosity is integral to intracellular freezing avoidance strategies in cold acclimated herbaceous cells.


Assuntos
Allium , Cálcio , Aclimatação , Cloreto de Cálcio , Parede Celular , Temperatura Baixa , Congelamento , Pectinas , Plantas , Temperatura
3.
Planta ; 250(5): 1567-1590, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31372744

RESUMO

MAIN CONCLUSION: Persistent DNA damage in gamma-exposed Norway spruce, Scots pine and Arabidopsis thaliana, but persistent adverse effects at the organismal and cellular level in the conifers only. Gamma radiation emitted from natural and anthropogenic sources may have strong negative impact on plants, especially at high dose rates. Although previous studies implied different sensitivity among species, information from comparative studies under standardized conditions is scarce. In this study, sensitivity to gamma radiation was compared in young seedlings of the conifers Scots pine and Norway spruce and the herbaceous Arabidopsis thaliana by exposure to 60Co gamma dose rates of 1-540 mGy h-1 for 144 h, as well as 360 h for A. thaliana. Consistent with slightly less prominent shoot apical meristem, in the conifers growth was significantly inhibited with increasing dose rate ≥ 40 mGy h-1. Post-irradiation, the conifers showed dose-rate-dependent inhibition of needle and root development consistent with increasingly disorganized apical meristems with increasing dose rate, visible damage and mortality after exposure to ≥ 40 mGy h-1. Regardless of gamma duration, A. thaliana showed no visible or histological damage or mortality, only delayed lateral root development after ≥ 100 mGy h-1 and slightly, but transiently delayed post-irradiation reproductive development after ≥ 400 mGy h-1. In all species dose-rate-dependent DNA damage occurred following ≥ 1-10 mGy h-1 and was still at a similar level at day 44 post-irradiation. In conclusion, the persistent DNA damage (possible genomic instability) following gamma exposure in all species may suggest that DNA repair is not necessarily mobilized more extensively in A. thaliana than in Norway spruce and Scots pine, and the far higher sensitivity at the organismal and cellular level in the conifers indicates lower tolerance to DNA damage than in A. thaliana.


Assuntos
Arabidopsis/efeitos da radiação , Raios gama/efeitos adversos , Picea/efeitos da radiação , Pinus sylvestris/efeitos da radiação , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Noruega , Picea/genética , Picea/crescimento & desenvolvimento , Pinus sylvestris/genética , Pinus sylvestris/crescimento & desenvolvimento , Plântula/genética , Plântula/efeitos da radiação
4.
Photochem Photobiol Sci ; 18(2): 387-399, 2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30480699

RESUMO

Growth in high relative air humidity (RH, >85%) affects plant morphology and causes diminished response to stomatal closing signals. Many greenhouses are prone to high RH conditions, which may negatively affect production and post-harvest quality. UV radiation induces stomatal closure in several species, and facilitates disease control. We hypothesised that UV exposure may trigger stomatal closure in pea plants (Pisum sativum) grown in high RH, thereby restoring stomatal function. The effects of UV exposure were tested on plants grown in moderate (60%) or high (90%) RH. UV exposure occurred at night, according to a disease control protocol. Lower stomatal conductance rates were found in UV-exposed plants, though UV exposure did not improve the rate of response to closing stimuli or desiccation tolerance. UV-exposed plants showed leaf curling, chlorosis, necrosis, and DNA damage measured by the presence of cyclobutane pyrimidine dimers (CPD), all of which were significantly greater in high RH plants. These plants also had lower total flavonoid content than moderate RH plants, and UV-exposed plants had less than controls. Plants exposed to UV had a higher content of cuticular layer uronic compounds than control plants. However, high RH plants had a higher relative amount of cuticular waxes, but decreased proteins and uronic compounds. Plants grown in high RH had reduced foliar antioxidant power compared to moderate RH. These results indicate that high RH plants were more susceptible to UV-induced damage than moderate RH plants due to reduced flavonoid content and oxidative stress defence.


Assuntos
Ar , Antioxidantes/metabolismo , Dano ao DNA , Flavonoides/metabolismo , Umidade , Pisum sativum/efeitos da radiação , Folhas de Planta/efeitos da radiação , Pisum sativum/genética , Pisum sativum/metabolismo , Folhas de Planta/genética , Folhas de Planta/metabolismo
5.
Photochem Photobiol Sci ; 18(8): 1945-1962, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31305802

RESUMO

Exposure to ambient UV-B radiation may prime protective responses towards various stressors in plants, though information about interactive effects of UV-B and gamma radiation is scarce. Here, we aimed to test whether UV-B exposure could prime acclimatisation mechanisms contributing to tolerance to low-moderate gamma radiation levels in Scots pine seedlings, and concurrently whether simultaneous UV-B and gamma exposure may have an additive adverse effect on seedlings that had previously not encountered either of these stressors. Responses to simultaneous UV-B (0.35 W m-2) and gamma radiation (10.2-125 mGy h-1) for 6 days with or without UV-B pre-exposure (0.35 W m-2, 4 days) were studied across various levels of organisation, as compared to effects of either radiation type. In contrast to UV-B, and regardless of UV-B presence, gamma radiation at ≥42.9 mGy h-1 caused increased formation of reactive oxygen species and reduced shoot length, and reduced root length at 125 mGy h-1. In all experiments there was a gamma dose rate-dependent increase in DNA damage at ≥10.8 mGy h-1, generally with additional UV-B-induced damage. Gamma-induced growth inhibition and gamma- and UV-B-induced DNA damage were still visible 44 days post-irradiation, even at 20.7 mGy h-1, probably due to genomic instability, but this was reversed after 8 months. In conclusion, there was no evidence of a protective effect of UV-B on gamma-induced growth inhibition and DNA damage in Scots pine, and no additive adverse effect of gamma and UV-B radiation on growth in spite of the additional UV-B-induced DNA damage.


Assuntos
Raios gama , Pinus sylvestris/crescimento & desenvolvimento , Pinus sylvestris/efeitos da radiação , Plântula/crescimento & desenvolvimento , Plântula/efeitos da radiação , Raios Ultravioleta
6.
Plant Cell Physiol ; 58(3): 466-477, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-28028164

RESUMO

Thermoperiodism is defined as the ability to discriminate between day temperature (DT) and night temperature (NT). Our aim was to shed light on the mechanistic basis of thermoperiodic floral induction with acceleration under lower DT than NT compared with other DT-NT combinations at the same average daily temperature (ADT), a response exploited in temperate area greenhouses. Arabidopsis thaliana floral pathway mutants and a lhy circadian clock mutant as well as the expression of floral integrators and LHY (LATE ELONGATED HYPOCOTYL) were studied under different DT-NT combinations, all at the same ADT. We show that acceleration of floral induction under lower DT than NT is linked to increased FT expression early during the day and generally increased LFY expression preceding visible flower buds, compared with higher DT than NT or equal DT and NT. Consistent with FLOWERING LOCUS T (FT) action through LEAFY (LFY), time to floral transition in ft-1 and lfy-1 was similar under all treatments, in contrast to the situation for soc1-1, which behaved like the wild type (WT). The lhy-21 mutants did not discriminate between opposite DT-NT combinations, whereas LHY expression in the WT differed in these temperature regimes. This might suggest that LHY plays a role in thermoperiodic control of floral induction. We conclude that thermoperiodic control of floral transition is associated with modulation of the diurnal expression patterns of FT, with timing of temperature alteration being important rather than ADT.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Arabidopsis/fisiologia , Flores/fisiologia , Temperatura , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Fatores de Tempo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
7.
Planta ; 246(3): 553-566, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28577177

RESUMO

MAIN CONCLUSION: Epigenetic memory affects the timing of bud burst phenology and the expression of bud burst-related genes in genetically identical Norway spruce epitypes in a manner usually associated with ecotypes. In Norway spruce, a temperature-dependent epigenetic memory established during embryogenesis affects the timing of bud burst and bud set in a reproducible and predictable manner. We hypothesize that the clinal variation in these phenological traits, which is associated with adaptation to growth under frost-free conditions, has an epigenetic component. In Norway spruce, dehydrins (DHNs) have been associated with extreme frost tolerance. DHN transcript levels decrease gradually prior to flushing, a time when trees are highly sensitive to frost. Furthermore, EARLY BUD BREAK 1 genes (EBB1) and the FT-TFL1-LIKE 2-gene (PaFTL2) were previously suggested to be implied in control of bud phenology. Here we report an analysis of transcript levels of 12 DHNs, 3 EBB1 genes and FTL2 in epitypes of the same genotype generated at different epitype-inducing temperatures, before and during spring bud burst. Earlier flushing of epitypes originating from embryos developed at 18 °C as compared to 28 °C, was associated with differential expression of these genes between epitypes and between buds and last year's needles. The majority of these genes showed significantly different expressions between epitypes in at least one time point. The general trend in DHN expression pattern in buds showed the expected reduction in transcript levels when approaching flushing, whereas, surprisingly, transcript levels peaked later in needles, mainly at the moment of bud burst. Collectively, our results demonstrate that the epigenetic memory of temperature during embryogenesis affects bud burst phenology and expression of the bud burst-related DHN, EBB1 and FTL2 genes in genetically identical Norway spruce epitypes.


Assuntos
Epigênese Genética/fisiologia , Picea/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Epigênese Genética/genética , Genes de Plantas/genética , Genes de Plantas/fisiologia , Picea/genética , Picea/fisiologia , Brotos de Planta/genética , Brotos de Planta/fisiologia , Reação em Cadeia da Polimerase em Tempo Real , Sementes/genética , Sementes/fisiologia , Temperatura , Transcriptoma
8.
Planta ; 243(5): 1237-49, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26895338

RESUMO

MAIN CONCLUSION: A significant number of epigenetic regulators were differentially expressed during embryogenesis at different epitype-inducing conditions. Our results support that methylation of DNA and histones, as well as sRNAs, are pivotal for the establishment of the epigenetic memory. As a forest tree species with long generation times, Norway spruce is remarkably well adapted to local environmental conditions despite having recently, from an evolutionary perspective, recolonized large areas following the last glaciation. In this species, there is an enigmatic epigenetic memory of the temperature conditions during embryogenesis that allows rapid adaptation to changing environment. We used a transcriptomic approach to investigate the molecular mechanisms underlying the formation of the epigenetic memory during somatic embryogenesis in Norway spruce. Nine mRNA libraries were prepared from three epitypes of the same genotype resulting from exposure to epitype-inducing temperatures of 18, 23 and 28 °C. RNA-Seq analysis revealed more than 10,000 differentially expressed genes (DEGs). The epitype-inducing conditions during SE were accompanied by marked transcriptomic changes for multiple gene models related to the epigenetic machinery. Out of 735 putative orthologs of epigenetic regulators, 329 were affected by the epitype-inducing temperatures and differentially expressed. The majority of DEGs among the epigenetic regulators was related to DNA and histone methylation, along with sRNA pathways and a range of putative thermosensing and signaling genes. These genes could be the main epigenetic regulators involved in formation of the epigenetic memory. We suggest considerable expansion of gene families of epigenetic regulators in Norway spruce compared to orthologous gene families in Populus and Arabidopsis. Obtained results provide a solid basis for further genome annotation and studies focusing on the importance of these candidate genes for the epigenetic memory formation.


Assuntos
Epigênese Genética , Regulação da Expressão Gênica de Plantas , Picea/genética , Sementes/genética , Cromatina/genética , Perfilação da Expressão Gênica , Biblioteca Gênica , Histonas/genética , Histonas/metabolismo , MicroRNAs , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , RNA Mensageiro , Reprodutibilidade dos Testes , Análise de Sequência de RNA , Transdução de Sinais/genética , Temperatura , Transcriptoma
9.
Plant Cell Environ ; 36(2): 382-92, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22812416

RESUMO

Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and ß-glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and ß-glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA-glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low ß-glucosidase activity converting ABA-GE to ABA. Continuous lighting (24 h) resulted in low levels of ß-glucosidase activity irrespective of RH, indicating that a dark period is essential to activate ß-glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that ß-glucosidase is a key enzyme regulating the ABA pool in rose plants.


Assuntos
Ácido Abscísico/metabolismo , Ar , Umidade , Luz , Estômatos de Plantas/fisiologia , Estômatos de Plantas/efeitos da radiação , Rosa/fisiologia , Ritmo Circadiano/efeitos da radiação , Escuridão , Dessecação , Fotoperíodo , Transpiração Vegetal/fisiologia , Transpiração Vegetal/efeitos da radiação , Rosa/efeitos da radiação , beta-Glucosidase/metabolismo
10.
Front Plant Sci ; 14: 1196806, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37546277

RESUMO

An epigenetic memory of the temperature sum experienced during embryogenesis is part of the climatic adaptation strategy of the long-lived gymnosperm Norway spruce. This memory has a lasting effect on the timing of bud phenology and frost tolerance in the resulting epitype trees. The epigenetic memory is well characterized phenotypically and at the transcriptome level, but to what extent DNA methylation changes are involved have not previously been determined. To address this, we analyzed somatic epitype embryos of Norway spruce clones produced at contrasting epitype-inducing conditions (18 and 28°C). We screened for differential DNA methylation in 2744 genes related mainly to the epigenetic machinery, circadian clock, and phenology. Of these genes, 68% displayed differential DNA methylation patterns between contrasting epitype embryos in at least one methylation context (CpG, CHG, CHH). Several genes related to the epigenetic machinery (e.g., DNA methyltransferases, ARGONAUTE) and the control of bud phenology (FTL genes) were differentially methylated. This indicates that the epitype-inducing temperature conditions induce an epigenetic memory involving specific DNA methylation changes in Norway spruce.

11.
Sci Total Environ ; 904: 166844, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37689207

RESUMO

The Chernobyl Nuclear Power Plant (ChNPP) accident in 1986 resulted in extremely high levels of acute ionising radiation, that killed or damaged Scots pine (Pinus sylvestris) trees in the surrounding areas. Dead trees were cleared and buried, and new plantations established a few years later. Today, more than three decades later, gamma and beta-radiation near the ChNPP is still elevated compared with ambient levels but have decreased by a factor of 300 and 100, respectively. In the present work, Scots pine-trees growing at High (220 µGy h-1), Medium (11 µGy h-1), and Low (0.2 µGy h-1) total (internal + external) dose rates of chronically elevated ionising radiation in the Chernobyl Exclusion zone were investigated with respect to possible damage to DNA, cells and organelles, as well as potentially increased levels of phenolic and terpenoid antioxidants. Scots pine from the High and Medium radiation sites had elevated levels of DNA damage in shoot tips and needles as shown by the COMET assay, as well as increased numbers of resin ducts and subcellular abnormalities in needles. Needles from the High radiation site showed elevated levels of monoterpenes and condensed tannins compared with those from the other sites. In conclusion, more than three decades after the ChNPP accident substantial DNA damage and (sub)cellular effects, but also mobilisation of stress-protective substances possessing antioxidant activity were observed in Scots pine trees growing at elevated levels of ionising radiation. This demonstrates that the radiation levels in the Red Forest still significantly impact the plant community.


Assuntos
Acidente Nuclear de Chernobyl , Pinus sylvestris , Pinus , Monitoramento de Radiação , Radiação Ionizante , Árvores , Florestas
12.
Plant Cell Environ ; 34(2): 332-46, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21054436

RESUMO

The molecular basis for terminal bud formation in autumn is not well understood in conifers. By combining suppression subtractive hybridization and monitoring of gene expression by qRT-PCR analysis, we aimed to identify genes involved in photoperiodic control of growth cessation and bud set in Norway spruce. Close to 1400 ESTs were generated and their functional distribution differed between short day (SD-12 h photoperiod) and long day (LD-24 h photoperiod) libraries. Many genes with putative roles in protection against stress appeared differentially regulated under SD and LD, and also differed in transcript levels between 6 and 20 SDs. Of these, PaTFL1(TERMINAL FLOWER LIKE 1) showed strongly increased transcript levels at 6 SDs. PaCCCH(CCCH-TYPE ZINC FINGER) and PaCBF2&3(C-REPEAT BINDING FACTOR 2&3) showed a later response at 20 SDs, with increased and decreased transcript levels, respectively. For rhythmically expressed genes such as CBFs, such differences might represent a phase shift in peak expression, but might also suggest a putative role in response to SD. Multivariate analyses revealed strong differences in gene expression between LD, 6 SD and 20 SD. The robustness of the gene expression patterns was verified in 6 families differing in bud-set timing under natural light with gradually decreasing photoperiod.


Assuntos
Regulação da Expressão Gênica de Plantas , Genes de Plantas/genética , Fotoperíodo , Picea/fisiologia , Brotos de Planta/fisiologia , Sequência de Bases , Escuridão , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Biblioteca Gênica , Luz , Anotação de Sequência Molecular , Dados de Sequência Molecular , Picea/genética , Picea/crescimento & desenvolvimento , Brotos de Planta/crescimento & desenvolvimento , Análise de Componente Principal , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência de DNA , Fatores de Tempo
13.
Plant J ; 60(4): 589-601, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19686536

RESUMO

Successful plant survival depends upon the proper integration of information from the environment with endogenous cues to regulate growth and development. We have investigated the interplay between ambient temperature and hormone action during the regulation of hypocotyl elongation, and we have found that gibberellins (GAs) and auxin are quickly and independently recruited by temperature to modulate growth rate, whereas activity of brassinosteroids (BRs) seems to be required later on. Impairment of GA biosynthesis blocked the increased elongation caused at higher temperatures, but hypocotyls of pentuple DELLA knockout mutants still reduced their response to higher temperatures when BR synthesis or auxin polar transport were blocked. The expression of several key genes involved in the biosynthesis of GAs and auxin was regulated by temperature, which indirectly resulted in coherent variations in the levels of accumulation of nuclear GFP-RGA (repressor of GA1) and in the activity of the DR5 reporter. DNA microarray and genetic analyses allowed the identification of the transcription factor PIF4 (phytochrome-interacting factor 4) as a major target in the promotion of growth at higher temperature. These results suggest that temperature regulates hypocotyl growth by individually impinging on several elements of a pre-existing network of signaling pathways involving auxin, BRs, GAs, and PIF4.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Giberelinas/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Temperatura , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , DNA de Plantas/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Hipocótilo/genética , Hipocótilo/crescimento & desenvolvimento , Ácidos Indolacéticos/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Transdução de Sinais , Esteroides/metabolismo
14.
Plant Mol Biol ; 73(1-2): 37-47, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20213333

RESUMO

In woody species cycling between growth and dormancy must be precisely synchronized with the seasonal climatic variations. Cessation of apical growth, resulting from exposure to short photoperiod (SD) and altered light quality, is gating the chain of events resulting in bud dormancy and cold hardiness. The relative importance of these light parameters, sensed by phytochromes and possibly a blue light receptor, varies with latitude. Early in SD, changes in expression of light signaling components dominate. In Populus active shoot elongation is linked to high expression of FLOWERING LOCUS T (FT) resulting from coincidence of high levels of CONSTANS and light at the end of days longer than a critical one. In Picea, PaFT4 expression increases substantially in response to SD. Thus, in contrast to Populus-FT, PaFT4 appears to function in inhibition of shoot elongation or promotion of growth cessation. Accordingly, different FT-genes appear to have opposite effects in photoperiodic control of shoot elongation. Reduction in gibberellin under SD is involved in control of growth cessation and bud formation, but not further dormancy development. Coinciding with formation of a closed bud, abscisic acid activity increases and cell-proliferation genes are down-regulated. When dormancy is established very few changes in gene expression occur. Thus, maintenance of dormancy is not dependent on comprehensive transcriptional regulation. In some species low temperature induces growth cessation and dormancy, in others temperature affects photoperiod requirement. The temperature under SD affects both the rate of growth cessation, bud formation and depth of dormancy. As yet, information on the molecular basis of these responses to temperature is scarce.


Assuntos
Luz , Fotoperíodo , Brotos de Planta/crescimento & desenvolvimento , Relógios Biológicos , Temperatura Baixa , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Giberelinas/metabolismo , Picea/genética , Picea/crescimento & desenvolvimento , Picea/efeitos da radiação , Reguladores de Crescimento de Plantas/metabolismo , Brotos de Planta/genética , Brotos de Planta/efeitos da radiação , Populus/genética , Populus/crescimento & desenvolvimento , Populus/efeitos da radiação , Transdução de Sinais
15.
J Exp Bot ; 61(4): 1015-29, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20022920

RESUMO

Active gibberellin (GA(1)) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA(1) compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la cry(s), this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la cry(s) were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la cry(s) plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.


Assuntos
Giberelinas/metabolismo , Fotossíntese , Pisum sativum/crescimento & desenvolvimento , Pisum sativum/metabolismo , Apraxia Ideomotora , Respiração Celular , Pisum sativum/química , Pisum sativum/genética , Folhas de Planta/química , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Caules de Planta/química , Caules de Planta/genética , Caules de Planta/crescimento & desenvolvimento , Caules de Planta/metabolismo , Transdução de Sinais , Temperatura
16.
Plant Physiol Biochem ; 47(2): 105-15, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19097801

RESUMO

In woody plants of the temperate zone short photoperiod (SD) leads to growth cessation. In angiosperms CONSTANS (CO) or CO-like genes play an important role in the photoperiodic control of flowering, tuberisation and shoot growth. To investigate the role of CO-like genes in photoperiodic control of shoot elongation in gymnosperms, PaCOL1 and PaCOL2 were isolated from Norway spruce. PaCOL1 encodes a 3.9kb gene with a predicted protein of 444 amino acids. PaCOL2 encodes a 1.2kb gene with a predicted protein of 385 amino acids. Both genes consist of two exons and have conserved domains found in other CO-like genes; two zinc finger domains, a CCT and a COOH domain. PaCOL1 and PaCOL2 fall into the group 1c clade of the CO-like genes, and are thus distinct from Arabidopsis CO that belongs to group 1a. Transcript levels of both PaCOL-genes appear to be light regulated, an increasing trend was observed upon transition from darkness to light, and a decreasing trend during darkness. The increasing trend at dawn was observed both in needles and shoot tips, whereas the decreasing trend in darkness was most prominent in shoot tips, and limited to the late part of the dark period in needles. The transcript levels of both genes decreased significantly in both tissues under SD prior to growth cessation and bud formation. This might suggest an involvement in photoperiodic control of shoot elongation or might be a consequence of regulation by light.


Assuntos
Regulação da Expressão Gênica de Plantas , Genes de Plantas , Fotoperíodo , Picea/genética , Proteínas de Plantas/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Escuridão , Genoma de Planta , Luz , Dados de Sequência Molecular , Picea/crescimento & desenvolvimento , Proteínas de Plantas/classificação , Alinhamento de Sequência , Fatores de Transcrição/química
17.
Front Plant Sci ; 8: 1046, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28659966

RESUMO

Adaptation of plants to local conditions that vary substantially within their geographic range is essential for seasonal timing of flowering, a major determinant of plant reproductive success. This study investigates photoperiodic responses in natural populations of Arabidopsis thaliana from high northern latitudes and their significance for local adaptation. Thirty lineages from ten local A. thaliana populations, representing different locations across an altitudinal gradient (2-850 m a.s.l.) in Norway, were grown under uniform controlled conditions, and used to screen for responses to five different photoperiods. We studied relationships between variation in photoperiodic sensitivity of flowering time, altitude, and climatic factors associated with the sites of origin. We found that variation in response to photoperiod is significantly correlated with altitude and climatic variables associated with the sites of origin of the populations. Populations originating from lower altitudes showed stronger photoperiodic sensitivity than populations from higher altitudes. Our results indicate that the altitudinal climatic gradient generates clinal variation in adaptive traits in A. thaliana.

18.
J Plant Physiol ; 211: 63-69, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28161560

RESUMO

Previous studies have shown that plants developed under high relative air humidity (RH>85%) develop malfunctioning stomata and therefor have increased transpiration and reduced desiccation tolerance when transferred to lower RH conditions and darkness. In this study, plants developed at high RH were exposed to daily VPD fluctuations created by changes in temperature and/or RH to evaluate the potential improvements in stomatal functioning. Daily periods with an 11°C temperature increase and consequently a VPD increase (vpd: 0.36-2.37KPa) reduced the stomatal apertures and improved the stomatal functionality and desiccation tolerance of the rosette plant Arabidopsis thaliana. A similar experiment was performed with only a 4°C temperature increase and/or a RH decrease on tomato. The results showed that a daily change in VPD (vpd: 0.36-1.43KPa) also resulted in improved stomatal responsiveness and decreased water usage during growth. In tomato, the most effective treatment to increase the stomatal responsiveness to darkness as a signal for closure was daily changes in RH without a temperature increase.


Assuntos
Ar , Arabidopsis/fisiologia , Escuridão , Dessecação , Umidade , Estômatos de Plantas/fisiologia , Solanum lycopersicum/fisiologia , Pressão de Vapor , Temperatura , Água
19.
Front Plant Sci ; 8: 2109, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29321789

RESUMO

Whereas long days (LDs) sustain shoot elongation, short days (SDs) induce growth cessation and formation of dormant buds in young individuals of a wide range of temperate and boreal tree species. In specific conifers, including Norway spruce, photoperiodic control of bud development is associated with the formation of a plate of thick-walled cells, denoted as the crown, at the base of the bud. Information about cellular characteristics of this crown region is limited. We aimed to test whether the crown region is an important SD-induced barrier ensuring dehydration of the developing winter bud by preventing water influx. Using microscopy and synchrotron techniques, we show here that under LD, cell walls in growing shoot tips had highly methyl-esterified homogalacturonan pectin. During SD-induced bud development, the homogalacturonan in the crown region was de-methyl-esterified, enabling Ca2+ binding and crosslinking, a process known to decrease cell wall water permeability by reducing pectin pore size. In addition, there was abundant callose deposition at plasmodesmata in the crown region, and xylem connections between the bud and the subtending shoot were blocked. Consistent with reduced water transport across the crown region into the bud, uptake of fluorescein in shoot tips was blocked at the base of the bud under SD. Upon transfer from SD to bud-break-inducing LD, these processes were reversed, and aquaporin transcript levels significantly increased in young stem tissue after 4 weeks under LD. These findings indicate that terminal bud development is associated with reduced water transport through decreased cell wall permeability and blocking of plasmodesmata and xylem connections in the crown structure. This provides further understanding of the regulatory mechanism for growth-dormancy cycling in coniferous tree species such as Norway spruce.

20.
Plant Biotechnol (Tokyo) ; 33(4): 297-307, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-31274991

RESUMO

In Arabidopsis, flowering is delayed under red light and induced under far red light and blue light. Studies suggest that the florigen, FLOWERING LOCUS T, is involved in the control of light quality-associated flowering in Arabidopsis. In petunia, similar to Arabidopsis, flowering is delayed under red light and induced under blue light, however its mechanism still remains unknown. Here we isolated a gene which has 75% amino acid sequence similarity with Arabidopsis FT (AtFT), named PehFT. By overexpressing PehFT in Arbidopsis and petunia, we tested its ability to induce flowering. Also, by conducting expression analyses of PehFT under different light quality treatments, we tested its response to light quality. We concluded that PehFT, like AtFT, is a gene which responds to photoperiod and light quality, but unlike AtFT, is not the main gene controlling the light quality-associated flowering.

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