Widespread translational control contributes to the regulation of Arabidopsis photomorphogenesis

Environmental ‘light’ has a vital role in regulating plant growth and development. Transcriptomic profiling has been widely used to examine how light regulates mRNA levels on a genome‐wide scale, but the global role of translational regulation in the response to light is unknown. Through a transcriptomic comparison of steady‐state and polysome‐bound mRNAs, we reveal a clear impact of translational control on thousands of genes, in addition to transcriptomic changes, during photomorphogenesis. Genes encoding ribosomal protein are preferentially regulated at the translational level, which possibly contributes to the enhanced translation efficiency. We also reveal that mRNAs regulated at the translational level share characteristics of longer half‐lives and shorter cDNA length, and that transcripts with a cis‐element, TAGGGTTT, in their 5′ untranslated region have higher translatability. We report a previously neglected aspect of gene expression regulation during Arabidopsis photomorphogenesis. The identities and molecular signatures associated with mRNAs regulated at the translational level also offer new directions for mechanistic studies of light‐triggered translational enhancement in Arabidopsis. Environmental light regulates and optimizes plant growth and development. Genomic profiling of polysome‐associated mRNA reveals that light stimulates dramatic changes in translational regulation, which contribute more to light‐induced gene expression changes than transcriptional regulation. Synopsis Environmental light regulates and optimizes plant growth and development. Genomic profiling of polysome‐associated mRNA reveals that light stimulates dramatic changes in translational regulation, which contribute more to light‐induced gene expression changes than transcriptional regulation. Translational control has a stronger impact on gene expression regulation than transcriptomic changes during photomorphogenesis in Arabidopsis. Transcriptional and translational regulations have complementary and distinct impacts on biochemical pathways and biological processes. Light‐mediated translational control prefers stable and shorter mRNAs. mRNAs with TAGGGTTT in their 5′ untranslated region have higher translatability.