Immunolocalization and Histocytopathological Effects of Xanthomonas arboricola pv. pruni on Naturally Infected Leaf and Fruit Tissues of Peach (Prunus persica L. Batsch)

Abstract

Immunofluorescence and cytohistochemical studies have been performed to understand the host-parasite relationships in the pathosystem: peach-Xanthomonas arboricola pv. pruni (Xap). Using a commercial immunodetection kit, Xap cells were specifically identified in tissues from infected leaves and fruits. Sections from infected leaves showed that the pathogen penetrates the mesophyll via stomata and develops in the intercellular spaces where it degrades the cell wall components. This leads to cell collapse and consequently to the formation of necrotic lesions. The same events have been noted in sections from infected fruits. However, the contaminated zones of mesocarp parenchyma exhibited cell dedifferentiation and generated somatic embryo-like structures. Sections from midrib samples collected at different distances from infected lamina revealed the presence of Xap cells in the sieve tubes and xylem suggesting a systemic trafficking of the pathogen. The results are discussed in terms of cytological effects and epidemiology of Xap.

Molecular characterization of peach PR genes and their induction kinetics in response to bacterial infection and signaling molecules

“…Although entry of Xcp through peach leaf stomata has already been demonstrated (Miles et al 1977;Aarrouf et al 2008), the role of the stomata in opposing such entry has not yet been investigated. Two peach cultivars, 'Venture' and 'BabyGold 5', are known for their field resistance and susceptibility, respectively, to bacterial spot disease.…”

“…The stomatal opening at 3 HPI and the spread of Xcp in the intercellular spaces of mesophyll cells is often followed by the degradation of cell wall components (Aarrouf et al 2008). Polysaccharides released from the degradation of cell walls might serve as DAMPs, leading eventually to the induction of defense responses in mesophyll cells.…”

“…Symptoms on leaves include necrotic spots and shot holes that may coalesce, leading to tree defoliation. The bacteria invade peach leaves through the stomata (Miles et al 1977;Aarrouf et al 2008), which historically have been considered as passive barriers for the entry of pathogenic bacteria. Recent studies suggest an active role for stomata in restricting bacterial invasion (Underwood et al 2007).…”

Genómica comparativa de cepas de Xanthomonas arboricola asociada a Prunus spp.: caracterización de los procesos de infección de la mancha bacteriana de frutales de hueso y almendro

“…pruni, los estudios realizados con microscopía electrónica (Plessis, 1984), inmulocalización y la histocitopatología (Aarrouf et al, 2008), han permitido determinar cómo se da el ingreso y la colonización del tejido por parte de la bacteria tanto en ciruelo como en melocotonero.…”

“…De igual manera, se determinó que la bacteria es capaz de dirigirse de manera sistémica hasta el tejido meristemático de los brotes. Posteriormente, en melocotonero (Aarrouf et al, 2008), se demostró que el patógeno es capaz de ingresar al tejido del mesófilo a través de los estomas, colonizando el espacio intercelular, degradando los componentes de la pared celular, colapsando las células y dando lugar a lesiones necróticas. El análisis de secciones de la nervadura central tomadas a diversas distancias desde la lámina infectada, permitió observar la presencia de la bacteria en los tubos cribosos y en el xilema lo que podría sugerir el tráfico sistémico del patógeno.…”