DOG1 expression is predicted by the seed-maturation environment and contributes to geographical variation in germination in Arabidopsis thaliana.

Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
Molecular Ecology (Impact Factor: 6.28). 08/2011; 20(16):3336-49. DOI: 10.1111/j.1365-294X.2011.05181.x
Source: PubMed

ABSTRACT Seasonal germination timing of Arabidopsis thaliana strongly influences overall life history expression and is the target of intense natural selection. This seasonal germination timing depends strongly on the interaction between genetics and seasonal environments both before and after seed dispersal. DELAY OF GERMINATION 1 (DOG1) is the first gene that has been identified to be associated with natural variation in primary dormancy in A. thaliana. Here, we report interaccession variation in DOG1 expression and document that DOG1 expression is associated with seed-maturation temperature effects on germination; DOG1 expression increased when seeds were matured at low temperature, and this increased expression was associated with increased dormancy of those seeds. Variation in DOG1 expression suggests a geographical structure such that southern accessions, which are more dormant, tend to initiate DOG1 expression earlier during seed maturation and achieved higher expression levels at the end of silique development than did northern accessions. Although elimination of the synthesis of phytohormone abscisic acid (ABA) results in the elimination of maternal temperature effects on dormancy, DOG1 expression predicted dormancy better than expression of genes involved in ABA metabolism.

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    ABSTRACT: Background and AimsSeed yield and dormancy status are key components of species fitness that are influenced by the maternal environment, in particular temperature. Responses to environmental conditions can differ between ecotypes of the same species. Therefore, to investigate the effect of maternal environment on seed production, this study compared two contrasting Arabidopsis thaliana ecotypes, Cape Verdi Isle (Cvi) and Burren (Bur). Cvi is adapted to a hot dry climate and Bur to a cool damp climate, and they exhibit winter and summer annual phenotypes, respectively.Methods Bur and Cvi plants were grown in reciprocal controlled environments that simulated their native environments. Reproductive development, seed production and subsequent germination behaviour were investigated. Measurements included: pollen viability, the development of floral structure, and germination at 10 and 25 °C in the light to determine dormancy status. Floral development was further investigated by applying gibberellins (GAs) to alter the pistil:stamen ratio.Key ResultsTemperature during seed development determined seed dormancy status. In addition, seed yield was greatly reduced by higher temperature, especially in Bur (>90 %) compared with Cvi (approx. 50 %). The reproductive organs (i.e. stamens) of Bur plants were very sensitive to high temperature during early flowering. Viability of pollen was unaffected, but limited filament extension relative to that of the pistils resulted in failure to pollinate. Thus GA applied to flowers to enhance filament extension largely overcame the effect of high temperature on yield.Conclusions High temperature in the maternal environment reduced dormancy and negatively affected the final seed yield of both ecotypes; however, the extent of these responses differed, demonstrating natural variation. Reduced seed yield in Bur resulted from altered floral development not reduced pollen viability. Future higher temperatures will impact on seed performance, but the consequences may differ significantly between ecotypes of the same species.
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    ABSTRACT: How to cite this article: This article has been published as 'Eduardo Fernández-Pascual and Borja Jiménez-Alfaro Phenotypic plasticity in seed germination relates differentially to overwintering and flowering temperatures. Seed Science Research, Available on CJO 2014 doi:10.1017/ S0960258514000269' Copyright Cambridge University Press 2014 Original: Phenotypic plasticity in seed dormancy may allow plant species to cope with rapid environmental changes, such as climate warming. In controlled experimental settings, plasticity in dormancy has been found to relate to temperature during seed maturation, but this relationship has not been tested in field conditions. Here we analyse for the first time the variation in dormancy during five successive years in wild populations of the study species Centaurium somedanum, to determine how this variation is related to average temperatures during specific seasons of plant activity. We performed laboratory germination experiments to measure: (1) the degree of dormancy at dispersal; and (2) the sensitivity to dormancybreaking factors. We calculated average temperatures during four seasons of plant activity (overwintering, vegetative growth, flowering and seed maturation) for each year, and tested the relationship between these temperatures and patterns of dormancy variation, using Generalized Linear Models. Dormancy varied among sites and years, seeds being more dormant in colder years. For the degree of dormancy at dispersal, we found a positive relationship with flowering temperature and a significant effect of collection site. For the sensitivity to dormancy-breaking factors, we found no significant differences among sites, a positive relationship with flowering temperature and a negative relationship with overwintering temperature. Phenotypic plasticity in dormancy in C. somedanum is thus especially marked in the sensitivity to dormancybreaking factors. Temperatures during overwintering and flowering have differential effects on this plasticity, allowing the plant to detect the gradient of seasonality, a main ecological feature of its distribution. These results highlight the importance of taking into account more than average temperatures when assessing the response of plant phenotypic plasticity to climate change.
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    ABSTRACT: Seed dormancy is an important agronomic trait: low levels can cause premature germination, while too much can inhibit uniform germination. As an approach to controlling the seed dormancy level in crops, we used Triticeae DOG1-like genes as transgenes. DOG1 is an Arabidopsis gene that underlies natural variation in seed dormancy. We previously showed that although their sequence similarities to DOG1 were low, some cereal DOG1-like genes enhanced seed dormancy in Arabidopsis. Here, we introduced two DOG1-like genes, TaDOG1L4 from wheat and HvDOG1L1 from barley, individually into the wheat cultivar Fielder. Their overexpression under the control of a maize ubiquitin promoter enhanced the seed dormancy level while leaving other traits unchanged. TaDOG1L4 was more effective than HvDOG1L1, which accords with the previously revealed difference in the effectiveness of these two genes in Arabidopsis seed dormancy. Knockdown of endogenous TaDOG1L4 in Fielder using double-strand RNA interference decreased the seed dormancy level by several tens of percent. This result indicates that some degree of seed dormancy inherent in wheat is imparted by DOG1-like genes.
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