Аннотация:Significance Five noncoding small RNAs (sRNAs) called the Qrr1-5 sRNAs act at the heart of the Vibrio harveyi quorum-sensing cascade. The Qrr sRNAs posttranscriptionally regulate 20 mRNA targets. Here, we use a method we call RSort-Seq that is based on unbiased high-throughput screening to define the critical bases in Qrr4 that specify its function. The power of our study comes from using the screening results to pinpoint particular nucleotides for follow-up biological analyses that define function. Using this approach, we discover how Qrr4 differentially regulates two of its targets, luxO and luxR . We also show how this strategy can be used to identify intramolecular suppressor mutations. This approach can be applied to any sRNA and any mRNA target.