Browsing by Author "Carvalho, Raquel F."
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- On the physiological significance of alternative splicing events in higher plantsPublication . Carvalho, Raquel F.; Feijão, Carolina V.; Duque, PaulaAlternative splicing, which generates multiple transcripts from the same gene and potentially different protein isoforms, is a key posttranscriptional regulatory mechanism for expanding proteomic diversity and functional complexity in higher eukaryotes. The most recent estimates, based on whole transcriptome sequencing, indicate that about 95 % of human and 60 % of Arabidopsis multi-exon genes undergo alternative splicing, suggesting important roles for this mechanism in biological processes. However, while the misregulation of alternative splicing has been associated with many human diseases, its biological relevance in plant systems is just beginning to unfold. We review here the few plant genes for which the production of multiple splice isoforms has been reported to have a clear in vivo functional impact. These case studies implicate alternative splicing in the control of a wide range of physiological and developmental processes, including photosynthetic and starch metabolism, hormone signaling, seed germination, root growth and flowering, as well as in biotic and abiotic stress responses. Future functional characterization of alternative splicing events and identification of the transcripts targeted by major regulators of this versatile means of modulating gene expression should uncover the breadth of its physiological significance in higher plants.
- The Arabidopsis SR45 Splicing Factor, a Negative Regulator of Sugar Signaling, Modulates SNF1-Related Protein Kinase 1 StabilityPublication . Carvalho, Raquel F.; Szakonyi, Dóra; Simpson, Craig G.; Barbosa, Inês C.R.; Brown, John W.S.; Baena-González, Elena; Duque, PaulaThe ability to sense and respond to sugar signals allows plants to cope with environmental and metabolic changes by adjusting growth and development accordingly. We previously reported that the SR45 splicing factor negatively regulates glucose signaling during early seedling development in Arabidopsis thaliana Here, we show that under glucose-fed conditions, the Arabidopsis sr45-1 loss-of-function mutant contains higher amounts of the energy-sensing SNF1-Related Protein Kinase 1 (SnRK1) despite unaffected SnRK1 transcript levels. In agreement, marker genes for SnRK1 activity are upregulated in sr45-1 plants, and the glucose hypersensitivity of sr45-1 is attenuated by disruption of the SnRK1 gene. Using a high-resolution RT-PCR panel, we found that the sr45-1 mutation broadly targets alternative splicing in vivo, including that of the SR45 pre-mRNA itself. Importantly, the enhanced SnRK1 levels in sr45-1 are suppressed by a proteasome inhibitor, indicating that SR45 promotes targeting of the SnRK1 protein for proteasomal destruction. Finally, we demonstrate that SR45 regulates alternative splicing of the Arabidopsis 5PTase13 gene, which encodes an inositol polyphosphate 5-phosphatase previously shown to interact with and regulate the stability of SnRK1 in vitro, thus providing a mechanistic link between SR45 function and the modulation of degradation of the SnRK1 energy sensor in response to sugars.