Role of Extracellular Polysaccharide and Endoglucanase in Root Invasion and Colonization of Tomato Plants by Ralstonia solanacearum

Abstract

Ralstonia solanacearum is a soilborne plant pathogen that normally invades hosts through their roots and then systemically colonizes aerial tissues. Previous research using wounded stem infection found that the major factor in causing wilt symptoms was the high-molecular-mass acidic extracellular polysaccharide (EPS I), but the beta-1,4-endoglucanase (EG) also contributes to virulence. We investigated the importance of EPS I and EG for invasion and colonization of tomato by infesting soil of 4-week-old potted plants with either a wild-type derivative or genetically well-defined mutants lacking EPS I, EG, or EPS I and EG. Bacteria of all strains were recovered from surface-disinfested roots and hypocotyls as soon as 4 h after inoculation; that bacteria were present internally was confirmed using immunofluorescence microscopy. However, the EPS-minus mutants did not colonize stems as rapidly as the wild type and the EG-minus mutant. Inoculations of wounded petioles also showed that, even though the mutants multiplied as well as the wild type in planta, EPS-minus strains did not spread as well throughout the plant stem. We conclude that poor colonization of stems by EPS-minus strains after petiole inoculation or soil infestation is due to reduced bacterial movement within plant stem tissues.

CO2 assimilation, photosynthetic light response curves, and water relations of 'Pêra' sweet orange plants infected with Xylella fastidiosa

“…EPS-defective strains of Erwinia stewartii presented a reduced virulence partly because they spread more slowly than the wild type in the vascular system of maize plants (Braun, 1990). In a similar study, Saile et al (1997) used mutants to show that EPSs production increased the dissemination of Ralstonia solanacearum in tomato stem tissue. In a study with Pseudomonas syringae pv.…”

Priming by Rhizobacterium Protects Tomato Plants from Biotrophic and Necrotrophic Pathogen Infections through Multiple Defense Mechanisms

“…After Rs10703 inoculation, plants were return to the greenhouse. Disease assessment and estimation of pathogen growth in planta were carried out as described (Lin and Martin, 2005;Saile et al, 1997). Five days after inoculation, DC 3000 and speck numbers were estimated for five representative areas (2 × 2 cm 2 ) which showed discrete lesions.…”

Virulence strategies of phytopathogenic bacteria and their role in plant disease pathogenesis

“…The most enzymes in bacteria plant pathogen and fungi are those degrading the pectin substances which are also the widely studied as determinants (Collmer et al, 2002). Among the widely pectic enzymes in phytopathogenic bacteria are two important classes namely the pectate lyases (PL) and polygalacturonases (PG) (Collmer and Keen, 1986;Saile et al, 1997). The plant pathogens that secrete complexes of pectic enzymes such as the pectate lyases (PL) (Boch et al, 2002;Collmer et al, 2002) and polygalacturonases (PG) includes the soft rot Erwinias namely E. carotovora and E. chrysanthemi (Barras et al, 1994;Carpita and McCann, 2000;Collmer et al, 2002).…”