Endopathogenic lifestyle of Pseudomonas savastanoi pv. savastanoi in olive knots.
Bottom Line: The endophytic phase of Pseudomonas savastanoi pv. savastanoi in olive stems and the structural and ultrastructural histogenesis of olive knots have been studied.Hypertrophy of the stem tissue was concomitant with the formation of bacterial aggregates, microcolonies and multilayer biofilms, over the cell surfaces and the interior of plasmolysed cells facing the air-tissue interface of internal opened fissures, and was followed by invasion of the outer layers of the hypertrophied tissue.This is the first real-time monitoring of P. savastanoi disease development and the first illustrated description of the ultrastructure of P. savastanoi-induced knots.
Affiliation: Departamento de Biología Celular, Genética y Fisiología, Universidad de Málaga, Campus de Teatinos s/n, E-29071, Málaga, Spain.Show MeSH
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Mentions: Ultrathin knot sections of olive knots induced by NCPPB 3335‐GFP at 35 dpi were also analysed using high‐resolution transmission electron microscopy. Proliferation of P. savastanoi pv. savastanoi cells inside olive induced clearly visible modifications of the parenchymatous tissue, such as abnormal cell wall thickenings and intercellular spaces showing a degraded middle lamella. Moreover, bacterial cells were detected colonizing the intercellular spaces (Fig. 7A) and were in close contact to the degraded middle lamella (Fig. 7B) and primary cell wall (Fig. 7C), suggesting pathogen‐mediated degradation of these host cell structures. Parenchymatic‐like cells in contact with the pathogen usually showed a fibrillar and electrodense cytoplasm, probably due to the degeneration of cytoplasmatic organelles and plasma membranes (Fig. 7D and E).
Affiliation: Departamento de Biología Celular, Genética y Fisiología, Universidad de Málaga, Campus de Teatinos s/n, E-29071, Málaga, Spain.