Project description:Seed maturation, dormancy and germination are distinct physiological processes. Transition from maturation to dormancy, and from dormancy into germination are not only critical developmental phases in the plant life cycle but are also important agricultural traits. These developmental processes and their phase transitions are fine determined and coordinately regulated by genetic makeup and environmental cues. SCARECROW-LIKE15 (SCL15) has been demonstrated to be essential for repressing the seed maturation programme in vegetative tissues (Gao et al., Nat Commun, 2015, 6:7243). Here we report that SCL15 is also important for seed dormancy maintenance, germination timing and seed vigor performance based on the effects of SCL15 mutation on plant germination, growth and reproduction when compared with wild type Arabidopsis and over-expression lines 35S:SCL15 and Napin:SCL15. Seed dormancy is enhanced by the mutation of SCL15 in a GA signaling dependent way, indicating that SCL15 plays a negative role for primary dormancy release. Seed germination is positively regulated by SCL15 through interaction with ABA, GA and auxin signaling. SCL15 acts as positive regulator of seed vigor and effect of SCL15 mRNA abundance on seed reserve accumulation and seed development during late embryogenesis may contribute to the seed vigor performance.
Project description:Production of morphologically and physiologically variable seeds is an important strategy that helps plants to survive in unpredictable natural conditions. However, the model plant Arabidopsis thaliana and most agronomically essential crops yield visually homogenous seeds. Using automated phenotype analysis, we observed that in Arabidopsis small seeds tend to have higher primary and secondary dormancy levels when compared to large ones. Transcriptomic analysis revealed distinct gene expression profiles between large and small seeds. Large seeds had higher expression of translation-related genes implicated in germination competence. In contrast, small seeds showed elevated expression of many positive regulators of dormancy, including a key regulator of this process – the DOG1 gene. Differences in DOG1 expression were associated with differential production of its alternative cleavage and polyadenylation isoforms where in small seeds proximal poly(A) site is selected resulting in a short mRNA isoform. Furthermore, single-seed RNA-seq analysis demonstrated that large seeds resemble DOG1 knockout mutant seeds. Finally, on the single seed level, the expression of genes affected by seed size was correlated with the expression of genes positioning seeds on the path towards germination. Our results demonstrate an unexpected link between seed size and dormancy phenotypes in a species producing highly homogenous seed pools, suggesting that the correlation between seed morphology and physiology is more widespread than initially assumed.
Project description:The role of on-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the methylome of ddcc mutant in Arabidopsis dry seed using Illumina sequencing. Meanwhile, vegetative tissue, leaves from 3 week plant with ddcc mutant and from wild type, and dry seed from wild type plant were used as control. Illumina sequencing of bisulfite-converted genomic DNA from dry seed and 3-week-plant leaves of ddcc mutant and wild type.
Project description:The role of non-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the methylome of ddcc mutant in Arabidopsis postmature-green-stage seed and dry seed using Illumina sequencing. Meanwhile, vegetative tissue, leaves from 3 week plant with ddcc mutant and from wild-type, and postmature-green-stage seed and dry seed from wild-type plant were used as control.
Project description:Multiple factors control primary seed dormancy established during seed maturation and secondary seed dormancy established when a non-dormant seed is exposed to adverse conditions during imbibition. A key player in the control of both primary and secondary dormancy in Arabidopsis thaliana is the DOG1 gene, whose expression is extensively regulated at the transcriptional level. Despite its importance, the influence of posttranscriptional RNA processing and mRNA storage of DOG1 on the determination of dormancy depth remains elusive. We show that the UBA2A protein, a member of the hnRNP family, suppresses primary and secondary seed dormancy through the regulation of the DOG1 gene expres-sion at the posttranscriptional level. Surprisingly, single-molecule FISH, chromatin-attached RNA analysis and Pol II ChIP demonstrated that UBA2A do not control DOG1 gene transcription but rather DOG1 mRNA chromatin retention. Our study highlights chromatin retention as an important step in DOG1 gene expression regulation during dormancy establishment and shows that UBA2A like its human homolog hnRNPAB is implicated in RNA transport in the cell.
Project description:Seed dormancy in Arabidopsis is known to be mediated by the interaction of maternal and zygotic genomes during seed maturation. While studies have revealed the extensive influence of maternal processes on dormancy and germination, less is known about the influence of the father. Here we exploit differences in ploidy to explore the role of the paternal genome on progeny seed dormancy. We show that paternal genome acts to reduce seed dormancy regardless of maternal genome dose, resulting in lower dormancy in tetraploid Arabidopsis versus genetically identical diploids. We show that this paternal effect requires synthesis of RNA Polymerase IV-dependent RNAs in the male gametophyte which oppose the dormancy- inducing effects of maternal siRNAs on seed coat and endosperm development. We conclude that the paternal genome has evolved to subvert the dormancy-inducing role of the mother plant in progeny seeds.
Project description:There are four major seed developmental phases in Arabidopsis seed development: morphogenesis, maturation, dormancy and germination. What methylation changes occurring in the different phases, if any, remains unknown. To uncover the possible role of DNA methylation in different parts of the seed, we characterized the methylome of four major seed developmental phases of Arabidopsis using Illumina sequencing: global stage (glob) and linear cotyledon stage (lcot) for morphogenesis phase; mature green stage (mg) and post mature green stage (pmg) for maturation phase; dry seed (dry) for dormancy phase; leaves (leaf) from 4 week plant for vegetative tissues. Illumina sequencing of bisulfite-converted genomic DNA from six seed developmental stages in Arabidopsis: global stage (glob), linear cotyledon stage (lcot), mature green stage (mg), post mature green stage (pmg), dry seed (dry) and leaves (leaf) from 4 week plant.
Project description:There are four major seed developmental phases in Arabidopsis seed development: morphogenesis, maturation, dormancy and germination. What methylation changes occurring in the different phases, if any, remains unknown. To uncover the possible role of DNA methylation in different parts of the seed, we characterized the methylome of four major seed developmental phases of Arabidopsis using Illumina sequencing: global stage (glob) and linear cotyledon stage (lcot) for morphogenesis phase; mature green stage (mg) and post mature green stage (pmg) for maturation phase; dry seed (dry) for dormancy phase; leaves (leaf) from 4 week plant for vegetative tissues.
Project description:The role of on-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the transcriptome of ddcc mutant in Arabidopsis post-mature green seeds using Illumina sequencing. Meanwhile, post-mature green seeds from wild type were used as control.
Project description:Seeds establish dormancy to delay germination until the arrival of a favorable growing season. In this study, we identify a fate switch comprised of the MKK3–MPK7 kinase cascade and the ethylene response factor ERF4 that is responsible for the seed state transition from dormancy to germination. We show that dormancy-breaking factors activate the MKK3–MPK7 module, which affects the expression of some α-EXPANSIN (EXPA) genes to control seed dormancy. Furthermore, we identify a direct downstream substrate of this module, ERF4, which suppresses the expression of these EXPAs by directly binding to the GCC boxes in their exon regions. The activated MKK3–MPK7 module phosphorylates ERF4, leading to its rapid degradation and thereby releasing its inhibitory effect on the expression of these EXPAs. Collectively, our work identifies a signaling chain consisting of protein phosphorylation, degradation, and gene transcription, by which the germination promoters within the embryo sense and are activated by germination signals from ambient conditions.