LOV-DOMAIN PHOTORECEPTOR ATTENUATES VIRULENCE OF PSEUDOMONAS SYRINGAE IN LIGHT-EXPOSED LEAVES

ROMINA SELLARO; * VICTORIA MORICONI; WOLFGANG GARTNER; JORGE J. CASAL

Ciudad de Córdoba

Congreso; 16th International Congress on Photobiology; 2014

International Union of Photobiology

Light is important for plants as a source of energy and as a source of information perceived by sensory receptors [1]. Here we show that the light environment also affects plants indirectly, via the perception of these signals by their bacterial pathogens. To investigate the function of LOV-domain-regulated two-component system (Pst-Lov) of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), we produced two mutants of Δpst-lov. All the strains showed a similar growth pattern cultures in minimal medium and leaf of Arabidopsis in darkness. However, under white light, the wild-type strain showed a reduce growth than Δpst-lov mutant strains. We investigated the expression of principal and alternative sigma factors gene. Pst-Lov significantly reduced the expression of these genes under white light suggesting that Pst-Lov is a novel master negative regulator of gene expression in Pst DC3000. In contrast to previous observations [2], where photoreceptors enhance virulence, Pst-Lov actually attenuates virulence of Pst DC3000 by reducing invasiveness in leaf tissues. We speculate that on the one hand, the lack of light-Pst-Lov imposed growth restriction could keep the number of cells as high as possible reducing the chances of extinction of the soil population. On the other hand, the attenuated proliferation caused by light perception by Pst-Lov reduces Pst DC3000 damage to the light-exposed host leaf tissue, increasing the time available for dispersal to new hosts.