Vsr217 is a small
RNA from Vibrio tasmaniensis LGP32, a pathogen associated with mortality events affecting juvenile oysters. The vsr217 gene is located within the
5' untranslated region (UTR) of malK, encoding the
ATPase component of the
maltose importer, and is conserved within the genus Vibrio. In the presence of
maltose, vsr217 is regulated by MalT, the positive regulator of the
maltose regulon. vsr217 is required in cis for the full expression of malK. In addition, Vsr217 acts in trans to downregulate the expression of fbp encoding
fructose-1,6-bisphosphatase, an
enzyme involved in gluconeogenesis. Thus, in the presence of
maltose, the induction of Vsr217 is expected to promote glycolysis by negatively regulating the expression of a key
enzyme of gluconeogenesis. IMPORTANCE Juvenile pacific oysters have been subject in recent years to summer mortality episodes with deep economic consequences. The pathogen Vibrio tasmaniensis has been associated with such mortality events. For bacterial pathogens, survival within the host requires profound metabolic adaptations according to available resources. All kinds of regulatory elements, including noncoding RNAs, orchestrate this response. Oysters are rich in
glycogen, a precursor of
maltose, and we previously reported that V. tasmaniensis
maltose-regulated genes are strongly induced during oyster
infection. Here, we report the dual mechanism by which a small regulatory
RNA, generated from the
5' untranslated region of a gene belonging to the
maltose regulon, acts both in cis and trans. In cis, it stimulates growth on
maltose, and in trans, it downregulates the expression of a gene associated with gluconeogenesis, thus coordinating
maltose utilization with central
carbon metabolism.