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Proc Natl Acad Sci U S A. 2017 Aug 15;114(33):E7018-E7027. doi: 10.1073/pnas.1706379114. Epub 2017 Jul 31.

SPF45-related splicing factor for phytochrome signaling promotes photomorphogenesis by regulating pre-mRNA splicing in Arabidopsis.

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Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712.
The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712.
Department of Molecular Biology, Max Planck Institute for Developmental Biology, D-72076 Tübingen, Germany.
Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina, C1405BWE Buenos Aires, Argentina.
Plant Gene Expression Center, U.S. Department of Agriculture Agricultural Research Service, Albany, CA 94710.
Department of Plant & Microbial Biology, University of California, Berkeley, CA 94720.
Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712;


Light signals regulate plant growth and development by controlling a plethora of gene expression changes. Posttranscriptional regulation, especially pre-mRNA processing, is a key modulator of gene expression; however, the molecular mechanisms linking pre-mRNA processing and light signaling are not well understood. Here we report a protein related to the human splicing factor 45 (SPF45) named splicing factor for phytochrome signaling (SFPS), which directly interacts with the photoreceptor phytochrome B (phyB). In response to light, SFPS-RFP (red fluorescent protein) colocalizes with phyB-GFP in photobodies. sfps loss-of-function plants are hyposensitive to red, far-red, and blue light, and flower precociously. SFPS colocalizes with U2 small nuclear ribonucleoprotein-associated factors including U2AF65B, U2A', and U2AF35A in nuclear speckles, suggesting SFPS might be involved in the 3' splice site determination. SFPS regulates pre-mRNA splicing of a large number of genes, of which many are involved in regulating light signaling, photosynthesis, and the circadian clock under both dark and light conditions. In vivo RNA immunoprecipitation (RIP) assays revealed that SFPS associates with EARLY FLOWERING 3 (ELF3) mRNA, a critical link between light signaling and the circadian clock. Moreover, PHYTOCHROME INTERACTING FACTORS (PIFs) transcription factor genes act downstream of SFPS, as the quadruple pif mutant pifq suppresses defects of sfps mutants. Taken together, these data strongly suggest SFPS modulates light-regulated developmental processes by controlling pre-mRNA splicing of light signaling and circadian clock genes.


Arabidopsis; photomorphogenesis; phytochrome signaling; pre-mRNA splicing; splicing factor

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