O'Banion, B.; Carter, M. D.; Sanchez-Gallego, J. A.; Li, H.; Hayes, S. S.; Strysick, M.; Holcomb, J.; Allen, C.

<SPAN style=\"font-weight: 400;\">Bacteria use diverse sensors to integrate environmental stimuli into physiological responses that ensure fitness and survival. </SPAN><SPAN style=\"font-weight: 400;\">Ralstonia pseudosolanacearum</SPAN><SPAN style=\"font-weight: 400;\"> (</SPAN><SPAN style=\"font-weight: 400;\">Rps</SPAN><SPAN style=\"font-weight: 400;\">), a soil-borne plant pathogen that causes bacterial wilt disease, encodes a conserved LOV (light-oxygen-voltage) protein that mediates photoreception across the tree of life. However, </SPAN><SPAN style=\"font-weight: 400;\">Rps</SPAN><SPAN style=\"font-weight: 400;\"> had a minimal LOV-dependent transcriptional response to light in culture. Clues from functional domains, the </SPAN><SPAN style=\"font-weight: 400;\">{Delta}lov </SPAN><SPAN style=\"font-weight: 400;\">genomic neighborhood</SPAN><SPAN style=\"font-weight: 400;\">,</SPAN><SPAN style=\"font-weight: 400;\"> and transcriptional analyses suggest that LOV shapes </SPAN><SPAN style=\"font-weight: 400;\">Rps</SPAN><SPAN style=\"font-weight: 400;\"> biology in response to stress. Loss of LOV did not affect </SPAN><SPAN style=\"font-weight: 400;\">Rps</SPAN><SPAN style=\"font-weight: 400;\"> biofilm or motility </SPAN><SPAN style=\"font-weight: 400;\">in vitro</SPAN><SPAN style=\"font-weight: 400;\">, but influenced expression of genes encoding for these phenotypes</SPAN><SPAN style=\"font-weight: 400;\"> in planta</SPAN><SPAN style=\"font-weight: 400;\">. The </SPAN><SPAN style=\"font-weight: 400;\">{Delta}lov</SPAN><SPAN style=\"font-weight: 400;\"> mutant had</SPAN> <SPAN style=\"font-weight: 400;\">reduced heat tolerance and broad metabolic dysregulation, leading to growth defects on several carbon sources but a growth advantage in </SPAN><SPAN style=\"font-weight: 400;\">ex vivo</SPAN><SPAN style=\"font-weight: 400;\"> tomato xylem sap and in high-iron medium. </SPAN><SPAN style=\"font-weight: 400;\">In vitro</SPAN><SPAN style=\"font-weight: 400;\">, the </SPAN><SPAN style=\"font-weight: 400;\">{Delta}lov</SPAN><SPAN style=\"font-weight: 400;\"> mutant was more tolerant than wild-type of redox stress and the antimicrobial phenolic caffeate, but </SPAN><SPAN style=\"font-weight: 400;\">Rps</SPAN><SPAN style=\"font-weight: 400;\"> required </SPAN><SPAN style=\"font-weight: 400;\">{Delta}lov</SPAN><SPAN style=\"font-weight: 400;\"> for full virulence on tomato. LOV mediated attachment to the root surface, stem colonization, and overall symptom development. Together these findings reveal that LOV, which is highly conserved among plant pathogenic </SPAN><SPAN style=\"font-weight: 400;\">Ralstonia</SPAN><SPAN style=\"font-weight: 400;\">, modulates </SPAN><SPAN style=\"font-weight: 400;\">Rps </SPAN><SPAN style=\"font-weight: 400;\">stress response and virulence independently of light cues, but in a plant-dependent fashion.</SPAN>