Article

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: 6.49). 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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    • "Another naturally variable locus, FLOWERING LOCUS C (FLC), which was originally implicated in flowering time, has now been shown to influence dormancy as well (Chiang et al., 2009; Zhao, 2015). Both genes have been shown to be under selection via their effects on germination timing in the field in the USA (Chiang et al., 2009, 2011). Quantifying how seed-maturation temperatures and post-dispersal temperatures lead to phenotypic differentiation of these naturally occurring allelic variants will clarify their influence on phenology across the variable environments the species inhabits. "
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    ABSTRACT: The genetic basis of growth and development is often studied in constant laboratory environments; however, the environmental conditions that organisms experience in nature are often much more dynamic. We examined how daily temperature fluctuations, average temperature, day length and vernalization influence the flowering time of 59 genotypes of Arabidopsis thaliana with allelic perturbations known to affect flowering time. For a subset of genotypes, we also assessed treatment effects on morphology and growth. We identified 17 genotypes, many of which have high levels of the floral repressor FLOWERING LOCUS C (FLC), that bolted dramatically earlier in fluctuating - as opposed to constant - warm temperatures (mean = 22°C). This acceleration was not caused by transient VERNALIZATION INSENSITIVE 3-mediated vernalization, differential growth rates or exposure to high temperatures, and was not apparent when the average temperature was cool (mean = 12°C). Further, in constant temperatures, contrary to physiological expectations, these genotypes flowered more rapidly in cool than in warm environments. Fluctuating temperatures often reversed these responses, restoring faster bolting in warm conditions. Independently of bolting time, warm fluctuating temperature profiles also caused morphological changes associated with shade avoidance or 'high-temperature' phenotypes. Our results suggest that previous studies have overestimated the effect of the floral repressor FLC on flowering time by using constant temperature laboratory conditions.
    Full-text · Article · Dec 2015 · New Phytologist
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    • "Another naturally variable locus, FLOWERING LOCUS C (FLC), which was originally implicated in flowering time, has now been shown to influence dormancy as well (Chiang et al., 2009; Zhao, 2015). Both genes have been shown to be under selection via their effects on germination timing in the field in the USA (Chiang et al., 2009, 2011). Quantifying how seed-maturation temperatures and post-dispersal temperatures lead to phenotypic differentiation of these naturally occurring allelic variants will clarify their influence on phenology across the variable environments the species inhabits. "
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    ABSTRACT: Germination timing influences plant fitness, and its sensitivity to temperature may cause it to change as climate shifts. These changes are likely to be complex because temperatures that occur during seed maturation and temperatures that occur post-dispersal interact to define germination timing. We used the model organism Arabidopsis thaliana to determine how flowering time (which defines seed-maturation temperature) and post-dispersal temperature influence germination and the expression of genetic variation for germination. Germination responses to temperature (germination envelopes) changed as seeds aged, or after-ripened, and these germination trajectories depended on seed-maturation temperature and genotype. Different combinations of genotype, seed-maturation temperature, and after-ripening produced similar germination envelopes. Likewise, different genotypes and seed-maturation temperatures combined to produce similar germination trajectories. Differences between genotypes were most likely to be observed at high and low germination temperatures. The germination behavior of some genotypes responds weakly to maternal temperature but others are highly plastic. We hypothesize that weak dormancy induction could synchronize germination of seeds dispersed at different times. By contrast, we hypothesize that strongly responsive genotypes may spread offspring germination over several possible germination windows. Considering germination responses to temperature is important for predicting phenology expression and evolution in future climates.
    Full-text · Article · Oct 2015 · New Phytologist
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    • "Annona macroprophyllata is a species that grows in tropical deciduous forests in which the rainy and dry seasons are distinct; therefore, one adaptation for their survival is the timing of germination with the rainy season, which is possible with a dormancy period. Chiang et al. (2011) and Nakayabashi et al. (2012) noted that the degree of maturity of seeds can be induced by climatic factors, and in spontaneous conditions, plants must respond to changing conditions in time and space. If this is true, erratic germination and, consequently, the dormancy of A. macroprophyllata, constitutes a programmed strategy to adapt to small and large changes in the environment (a fact noted by Snyder, 2006; Donohue et al., 2010; Wang et al., 2012), allowing the survival of the species by controlling the propagation mechanisms in response to the close relationship that the species establish with the environment, using intricate ecological processes. "
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    ABSTRACT: Annona macroprophyllata (papausa or ilama) is an economically important species of fruit that is consumed in large quantities in Central America and is considered to have the finest flavour of all of the custard apples (Annonaceae). This species presents propagation problems including the six-month dormancy of the seeds, which has not been fully explained. Among the factors affecting the germination of Annona seeds are the position inside of the fruit and the presence of a micropylar woody plug. The present work addresses the importance of these factors in the germination and dormancy of this species, using a randomised design with seeds from 169 fruits of the white variety of Annona macroprophyllata. The fruits were divided into three sections (basal, middle, and apical) in which seeds were evaluated for nine months with the following parameters: the size and weight of the seeds and the viability and germination percentage considering the presence or absence of the micropylar plug. The results show no correlation between the breaking of dormancy and either the position of the seeds in the fruit or the micropylar plug, but they do establish the importance of the micropylar plug for germination. The breaking of dormancy requires storage for the length of the dry season in the tropical deciduous forest, the habitat of these plants.
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