The universal nine-amino-acid transactivation domains (9aaTADs) have been identified in numerous transcription activators. Here, we identified the conserved 9aaTAD motif in all nine members of the specificity protein (SP) family. Previously, the Sp1 transcription factor has been defined as a glutamine-rich activator. We showed by amino acid substitutions that the glutamine residues are completely dispensable for 9aaTAD function and are not conserved in the SP family. We described the origin and evolutionary history of 9aaTADs. The 9aaTADs of the ancestral Sp2 gene became inactivated in early chordates. We next discovered that an accumulation of valines in 9aaTADs inactivated their transactivation function and enabled their strict conservation during evolution. Subsequently, in chordates, Sp2 has duplicated and created new paralogs, Sp1, Sp3, and Sp4 (the SP1-4 clade). During chordate evolution, the dormancy of the Sp2 activation domain lasted over 100 million years. The dormant but still intact ancestral Sp2 activation domains allowed diversification of the SP1-4 clade into activators and repressors. By valine substitution in the 9aaTADs, Sp1 and Sp3 regained their original activator function found in ancestral lower metazoan sea sponges. Therefore, the vertebrate SP1-4 clade could include both repressors and activators. Furthermore, we identified secondary 9aaTADs in Sp2 introns present from fish to primates, including humans. In the gibbon genome, introns containing 9aaTADs were used as exons, which turned the Sp2 gene into an activator. Similarly, we identified introns containing 9aaTADs used conditionally as exons in the (SP family-unrelated) transcription factor SREBP1, suggesting that the intron-9aaTAD reservoir is a general phenomenon.
- MeSH
- Transcriptional Activation MeSH
- Gene Duplication MeSH
- Phylogeny MeSH
- Introns * genetics MeSH
- Humans MeSH
- Evolution, Molecular * MeSH
- Gene Expression Regulation * MeSH
- Amino Acid Sequence MeSH
- Sequence Homology MeSH
- Sp2 Transcription Factor * antagonists & inhibitors genetics metabolism MeSH
- Valine genetics metabolism MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
The universal nine-amino-acid transactivation domains (9aaTADs) have been identified in numerous transcription activators. Here, we identified the conserved 9aaTAD motif in all nine members of the specificity protein (SP) family. Previously, the Sp1 transcription factor has been defined as a glutamine-rich activator. We showed by amino acid substitutions that the glutamine residues are completely dispensable for 9aaTAD function and are not conserved in the SP family. We described the origin and evolutionary history of 9aaTADs. The 9aaTADs of the ancestral Sp2 gene became inactivated in early chordates. We next discovered that an accumulation of valines in 9aaTADs inactivated their transactivation function and enabled their strict conservation during evolution. Subsequently, in chordates, Sp2 has duplicated and created new paralogs, Sp1, Sp3, and Sp4 (the SP1-4 clade). During chordate evolution, the dormancy of the Sp2 activation domain lasted over 100 million years. The dormant but still intact ancestral Sp2 activation domains allowed diversification of the SP1-4 clade into activators and repressors. By valine substitution in the 9aaTADs, Sp1 and Sp3 regained their original activator function found in ancestral lower metazoan sea sponges. Therefore, the vertebrate SP1-4 clade could include both repressors and activators. Furthermore, we identified secondary 9aaTADs in Sp2 introns present from fish to primates, including humans. In the gibbon genome, introns containing 9aaTADs were used as exons, which turned the Sp2 gene into an activator. Similarly, we identified introns containing 9aaTADs used conditionally as exons in the (SP family-unrelated) transcription factor SREBP1, suggesting that the intron-9aaTAD reservoir is a general phenomenon.
- MeSH
- Transcriptional Activation MeSH
- Gene Duplication MeSH
- Phylogeny MeSH
- Introns genetics MeSH
- Humans MeSH
- Evolution, Molecular * MeSH
- Gene Expression Regulation * MeSH
- Amino Acid Sequence MeSH
- Sequence Homology MeSH
- Sp2 Transcription Factor antagonists & inhibitors genetics metabolism MeSH
- Valine genetics metabolism MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
In angiosperms, genome size and nucleobase composition (GC content) exhibit pronounced variation with possible adaptive consequences. The hyperdiverse orchid family possessing the unique phenomenon of partial endoreplication (PE) provides a great opportunity to search for interactions of both genomic traits with the evolutionary history of the family. Using flow cytometry, we report values of both genomic traits and the type of endoreplication for 149 orchid species and compare these with a suite of life-history traits and climatic niche data using phylogeny-based statistics. The evolution of genomic traits was further studied using the Brownian motion (BM) and Ornstein-Uhlenbeck (OU) models to access their adaptive potential. Pronounced variation in genome size (341-54 878 Mb), and especially in GC content (23.9-50.5%), was detected among orchids. Diversity in both genomic traits was closely related to the type of endoreplication, plant growth form and climatic conditions. GC content was also associated with the type of dormancy. In all tested scenarios, OU models always outperformed BM models. Unparalleled GC content variation was discovered in orchids, setting new limits for plants. Our study indicates that diversity in both genome size and GC content has adaptive consequences and is tightly linked with evolutionary transitions to PE.
Vegetative dormancy, that is the temporary absence of aboveground growth for ≥ 1 year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.
