The small ORFeome of Tribolium castaneum reveals deeply conserved small ORFs broadly expressed across tissues

Small open reading frames (small ORFs/smORFs/sORFs) were historically overlooked due to their short length (1) in at least one sample, and 16.5% expressed in five or more libraries. Conserved small ORFs showed broader and more stable expression, while lineage-specific ones displayed restricted expression, mostly in gonads or embryos. Isoformic and small CDSs were the most widely expressed classes. Notably, 29 small ORFs exhibited transcriptional and translational support (Swiss-Prot and/or Ribo-seq), 28 being small CDSs. A total of 390 small ORFs had potential paralogs, supporting gene duplication as a mechanism for small ORF emergence. Altogether, our findings reinforce that small ORFs, contrary to initial assumptions, can be deeply conserved and potentially perform key roles in evolutionary processes.