DOG1 expression is predicted by the seed-maturation environment and contributes to geographical variation in germination in Arabidopsis thaliana.
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.
- SourceAvailable from: Yousry A El-KassabySeed Science Research 01/2014; · 1.85 Impact Factor
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ABSTRACT: Organisms develop through multiple life stages that differ in environmental tolerances. The seasonal timing, or phenology, of life-stage transitions determines the environmental conditions to which each life stage is exposed and the length of time required to complete a generation. Both environmental and genetic factors con-tribute to phenological variation, yet predicting their combined effect on life cycles across a geographic range remains a challenge. We linked submodels of the plasticity of individual life stages to create an in-tegrated model that predicts life-cycle phenology in complex envi-ronments. We parameterized the model for Arabidopsis thaliana and simulated life cycles in four locations. We compared multiple "ge-notypes" by varying two parameters associated with natural genetic variation in phenology: seed dormancy and floral repression. The model predicted variation in life cycles across locations that quali-tatively matches observed natural phenology. Seed dormancy had larger effects on life-cycle length than floral repression, and results suggest that a genetic cline in dormancy maintains a life-cycle length of 1 year across the geographic range of this species. By integrating across life stages, this approach demonstrates how genetic variation in one transition can influence subsequent transitions and the geo-graphic distribution of life cycles more generally. Plant life cycles are composed of multiple life stages (e.g., seed, vegetative, reproductive) that differ in environmental sensitivities and tolerances. In seasonal environments, the timing, or phenology, of life-stage transitions (e.g., germi-nation, flowering, seed dispersal) may have importantThe American Naturalist 02/2015; 93513(4). · 4.45 Impact Factor
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ABSTRACT: Variations in levels of seed dormancy among conspecific populations are poorly understood. We aim to determine the variations in the level of dormancy in Rosa multibracteata along an elevational gradient, and to analyze the mechanisms underlying seed dormancy. The study was conducted in an arid valley in the eastern Tibetan Plateau at five elevations: 1700, 1900, 2100, 2300 and 2500 m. Achene traits were measured and physiological levels of dormancy were determined by measuring germination percentages of achenes treated with H2SO4 scarification, warm stratification and cold stratification and combinations of those treatments. Achene size, mass and pericarp thickness increased with increasing elevation, but embryo width decreased with increasing in the arid valley. The level of dormancy generally increased with increasing elevation. The level of dormancy of the rose achenes is intermediate from sites at elevations of 1700, 1900 and 2100 m and deep at elevations of 2300 and 2500 m. Comprehensive analysis suggests that the elevational pattern of level of seed dormancy could be ascribed to intrinsically thicker pericarp and deeper physiological dormancy in the embryo, and extrinsically decreased temperature, increased precipitation and soil moisture at the higher elevations. The great variations of achene traits and levels of seed dormancy across elevations suggest a phenotypic differentiation exists within this rose species. Thus, habitat conditions and achene traits should be considered when selecting roses as materials used to propagate seedlings for ornamental purposes or plant restoration.Ecological Research 07/2014; 29(4):693-700. · 1.51 Impact Factor