Plants survive by responding and adapting to various signals from the environment, particularly to changes in light quality and intensity. These changes are sensed by chloroplasts in green tissues, which then communicate the information to the nucleus. According to the information received, gene expression within the nucleus is altered, thereby affecting the plant's growth, metabolism and other physiological processes. The EU-funded ASRNABIDOPHYS (Identification of light signaling components in the regulation of alternative splicing in plants) initiative discovered how light/dark information perceived by chloroplasts alters gene expression in the nucleus. Gene expression is commonly regulated by a mechanism called splicing. Genetic sequences called introns are removed from RNA, leaving behind exons that are combined to form the messenger RNA (mRNA) that is translated into protein. Although introns are removed from defined sections of RNA by molecules called spliceosomes, the intron/exon boundaries can vary to create different-sized exons containing different sequences. This process, called alternative splicing, means that a range of proteins can be produced from the same mRNA. In a previous project, ASRNABIDOPHYS researchers discovered that a light-generated signal from a plant's chloroplasts regulates gene expression by controlling alternative splicing in the nucleus. This light-regulated splicing occurred even in the roots, but only via communication from photosynthetic tissues in the leaves. To uncover which molecules travel from shoots to roots to communicate light/dark information to root nuclei, researchers looked for splicing mutants in the plant Arabidopsis. By identifying mutations that affected light/dark-regulated splicing, they narrowed down candidates for factors influencing alternative splicing. Interestingly, ASRNABIDOPHYS found that the light-regulated signal affects alternative splicing of RNA-processing genes that are themselves required for splicing. This study has helped to unravel evolutionarily conserved strategies and new mechanisms for how plants regulate gene expression through alternative splicing.
Gene expression, plants, chloroplasts, ASRNABIDOPHYS, light signalling, alternative splicing