Effect of light on the physiological characteristics of Ralstonia pseudosolanacearum during the colonization of tomato plants.

TANO, JOSEFINA; RIPA, MARÍA BELÉN; FERREIRA, VIRGINA; PETROCELLI, SILVANA; RODRIGUEZ, MARÍA VICTORIA; ORELLANO, ELENA G.; TONDO, MARÍA LAURA; CARRAU, ANALÍA; SIRI, MARÍA INÉS

Águas de Lindóia

Congreso; 48a. Reunião Anual da SBBq; 2019

Sociedade Brasileira de Bioquímica e Biologia Molecular (SBBq)

Light perception is achieved by photoreceptor proteins, which trigger the signal transduction cascades that regulate light responses. LOV (Light, Oxygen or Voltage) photoreceptors are flavin-binding proteins using flavin mononucleotide (FMN) as chromophore. Ralstonia pseudosolanacearum (Rso) is a phytopathogen responsible for bacterial wilt in different crops of great agronomic importance such as potato and tomato. In the Rso genome there is one gene encoding a putative transmembrane LOV protein: Rsp0254. The aim of this work was to study the role of light and the LOV photoreceptor in the Rso physiology during bacterial wilt disease. The expression of the Rsp0254 gene of Rso GMI1000 strain was analyzed under white light and darkness. In addition, the transcriptional regulation of the lov gene was evaluated in order to determine whether this gene is controlled by the global regulators of the Rso virulence network. For this, a lov::lacZ reporter fusion was generated and introduced into different genetic mutant backgrounds (ΔhrpG, ΔpehR, ΔvsrA) The β-galactosidase activity of the reporter strains was measured under different light conditions. Moreover, physiological parameters involved in the virulence of Rso such as motility, biofilm, oxidative stress, adhesion and exopolysaccharide production were also determined. Finally, the capacity of infection of tomato plants (Solanum lycopersicum var. Minitomato) by Rso grown at different light conditions was studied. The results obtained revealed that the lov gene is expressed in the two light conditions tested and that HrpG regulates its transcriptional expression. Rso exhibited lower adhesion capacity, motility, biofilm formation and EPS production under white light. Tomato plants infected with Rso showed different bacterial wilt symptoms depending on the light treatment. These results demonstrate that the lov gene of Rso GMI1000 is functional and would be involved in the regulation of physiological characteristics required for colonization of the host plant.