There is an expanding list of examples by which one mRNA can 
posttranscriptionally influence the expression of others. This can involve RNA 
sponges that sequester regulatory RNAs of mRNAs in the same regulon, but the 
underlying molecular mechanism of such mRNA cross talk remains little 
understood. Here, we report sponge-mediated mRNA cross talk in the 
posttranscriptional network of GcvB, a conserved Hfq-dependent small RNA with 
one of the largest regulons known in bacteria. We show that mRNA decay from the 
gltIJKL locus encoding an amino acid ABC transporter generates a stable fragment 
(SroC) that base-pairs with GcvB. This interaction triggers the degradation of 
GcvB by RNase E, alleviating the GcvB-mediated mRNA repression of other amino 
acid-related transport and metabolic genes. Intriguingly, since the gltIJKL mRNA 
itself is a target of GcvB, the SroC sponge seems to enable both an internal 
feed-forward loop to activate its parental mRNA in cis and activation of many 
trans-encoded mRNAs in the same pathway. Disabling this mRNA cross talk affects 
bacterial growth when peptides are the sole carbon and nitrogen sources.