Figure 4. smORFs have varied functions flies.

a) smORF discovery was stimulated by the identification of the tarsal-less (tal) gene²⁹, which is also known as polished rice (pri)³⁰. The loss of tal/pri which leads to a truncated leg and a loss of the tarsus. Analysis of the tal gene revealed four homologous smORFs (ORF1A, 2A, 3A, and AA). The SEPs generated from these smORFs are as short as 11 amino acids and are conserved throughout evolution. b) Gene conservation led to the discovery of the smORF encoding sarcolamban³². The Sarcolamban regulates calcium flux by binding to the P60A SERCA ion channel. In the flies, loss of sarcolamban (KO) results in cardiac arrhythmia and overexpression (OX) leads to an increased heart rate to show a direct effect for these smORF in fly muscle function.