5 research outputs found
The transcriptional regulator BBX24 impairs DELLA activity to promote shade avoidance in Arabidopsis thaliana
[EN] In response to canopy shade, plant vegetative structures elongate to gain access to light. However, the mechanism that allows a plastic transcriptional response to canopy shade light is not fully elucidated. Here we propose that the activity of PIF4, a key transcription factor in the shade signalling network, is modulated by the interplay between the BBX24 transcriptional regulator and DELLA proteins, which are negative regulators of the gibberellin (GA) signalling pathway. We show that GA-related targets are enriched among genes responsive to BBX24 under shade and that the shade-response defect in bbx24 mutants is rescued by a GA treatment that promotes DELLA degradation. BBX24 physically interacts with DELLA proteins and alleviates DELLA-mediated repression of PIF4 activity. The proposed molecular mechanism provides reversible regulation of the activity of a key transcription factor that may prove especially relevant under fluctuating light conditions.We thank Santiago Mora Garcia for valuable initial discussions and Peter Quail for the PIL1::LUC construct. This work was supported by grants from Agencia Nacional de Promocion Cientifica y Tecnologica, and Universidad de Buenos Aires (to J.F.B), and the Spanish Ministry of Science, BIO2010-15071 (to M.A.B.).Crocco, C.; Locascio ., AAM.; Escudero, CM.; Alabadí Diego, D.; Blazquez Rodriguez, MA.; Botto, J. (2015). The transcriptional regulator BBX24 impairs DELLA activity to promote shade avoidance in Arabidopsis thaliana. Nature Communications. 6:1-10. https://doi.org/10.1038/ncomms7202S1106Valladares, F. & Niinemets, U. Shade tolerance, a key plant feature of complex nature and consequences. Annu. Rev. Ecol. Evol. Syst. 39, 237–257 (2008).Casal, J. J. 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Demographic history and genetic diversity of modern and herbarium collections of Arabidopsis thaliana from the Southern Hemisphere
The model plant, Arabidopsis thaliana, has a native range throughout Eurasia and North Africa and introduced populations have been found on several additional continents. Through the RegMap and 1001 Genomes projects, high resolution genetic data has been obtained for thousands of A. thaliana populations that are mostly distributed throughout the Northern Hemisphere. To gain insight into the genetic variation and demographic history of introduced populations of A. thaliana in the Southern Hemisphere, we collected plants from four ecologically diverse sites at the southernmost end of the species distribution in Patagonia, Argentina. Two of the sites were spaced 5 km apart on the south side of Lake Buenos Aires and two neighboring sites were selected 70 km away on the north side of the lake. Individuals collected exhibited a wide range of phenotypic characteristics. We analyzed the genetic diversity by low-resolution SNP genotyping and whole-genome sequencing. We also performed whole-genome sequencing of the DNA from an herbarium specimen collected from this region in 1967. We found that individuals from all four present-day populations were essentially genetically uniform across 149 SNP markers. Whole-genome sequencing revealed that only a small fraction of the genome was segregating among these strains. Genetic comparisons with the RegMap panel and 1001 Genomes data suggested a likely European origin for these populations. Sequencing data from the herbarium specimen revealed that the presentday populations are essentially the same as they were nearly half a century ago. We conclude that populations of A. thaliana in Patagonia were likely founded by an extremely small number of individuals and that phenotypic plasticity may have contributed to their persistence in the region despite their limited genetic diversity
Faithful modeling of transient expression and its application to elucidating negative feedback regulation
Modeling and analysis of genetic regulatory networks is essential both for better understanding their dynamic behavior and for elucidating and refining open issues. We hereby present a discrete computational model that effectively describes the transient and sequential expression of a network of genes in a representative developmental pathway. Our model system is a transcriptional cascade that includes positive and negative feedback loops directing the initiation and progression through meiosis in budding yeast. The computational model allows qualitative analysis of the transcription of early meiosis-specific genes, specifically, Ime2 and their master activator, Ime1. The simulations demonstrate a robust transcriptional behavior with respect to the initial levels of Ime1 and Ime2. The computational results were verified experimentally by deleting various genes and by changing initial conditions. The model has a strong predictive aspect, and it provides insights into how to distinguish among and reason about alternative hypotheses concerning the mode by which negative regulation through Ime1 and Ime2 is accomplished. Some predictions were validated experimentally, for instance, showing that the decline in the transcription of IME1 depends on Rpd3, which is recruited by Ime1 to its promoter. Finally, this general model promotes the analysis of systems that are devoid of consistent quantitative data, as is often the case, and it can be easily adapted to other developmental pathways