Ultrastructural and cell wall modifications during infection of Eucalyptus viminalis roots by a pathogenic Fusarium oxysporum strain

Abstract

Fusarium species are soil-borne fungal pathogens that produce a variety of disease symptoms when attacking crop plants. The mode of root colonization of Eucalyptus viminalis seedlings by a pathogenic F. oxyporum strain (Foeu1) at the ultrastructural level and changes in cell wall pectin during host pathogen interactions are described. Root systems of E. viminalis plants were inoculated with F. oxysporum in an in vitro model system. Hyphae of F. oxysporum adhered to the outer epidermal cell walls through fibrillar material, and after penetration they spread into the internal tissues. They developed intercellularly and intracellularly in the root cortex and invaded vascular tissues. Papillae were induced, and the host plasma membrane ruptured in colonized cells, causing rapid host tissue and cell damage. Changes in distribution and occurrence of nonesterified and methyl-esterified pectins were evaluated after root colonization by F. oxysporum using two monoclonal antibodies, JIM 5 and JIM 7, respectively. Nonesterified pectin in control roots was mainly localized in the epidermal cell walls and middle lamellae in parenchymal cortex, whereas methyl-esterified pectin accumulated more in primary cell walls of the cortex and phloem. Decreases in immunodetected nonesterified and methyl-esterified pectins were associated with extensive plant tissue degradation after root colonization by the pathogenic fungus.

Wound-induced pectin methylesterases enhance banana (Musa spp. AAA) susceptibility to Fusarium oxysporum f. sp. cubense

“…Degeneration of HGs recognized by the antibodies JIM5 and JIM7 was the usual response of most plants to the pathogen (Salerno et al ., 2004; Boudjeko et al ., 2006; Curvers et al ., 2010; Digonnet et al ., 2012); however, an increase in the labeling by JIM7 was also reported (Simon et al ., 2005). In the present study, PMEs, pectin DMs, and individual HG levels all showed dynamic changes.…”

Changes in cell wall ultrastructure induced by sudden flooding at 25°C inPisum sativum(Fabaceae) primary roots

“…The degree and pattern of methyl esterification vary among plants, tissues and even within a single cell wall based on the functional requirements for HGs (Rose, 2003; Willats et al, 2006). The quantity and/or distribution patterns of HGs in cell walls have been observed to change during many of the developmental processes mentioned (Stephenson and Hawes, 1994; Roberts et al, 2000), in defense against pathogens (Salerno and Gianinazzi, 2004) and in response to abiotic stress such as Al‐induced root inhibition and hypoxia‐induced cortical aerenchyma formation (Le Van et al, 1994; Gunawardena et al, 2001b). The complex changes in cell wall ultrastructure during warm temperature and flooding‐induced vascular cavity formation have never been characterized.…”

Cell interactions between a nonpathogenic Fusarium oxysporum strain and root tissues of Eucalyptus viminalis

“…Furthermore, the increased accumulation of NE pectin in cell walls across infected roots may be indicative of cell wall strengthing in the tissues. These observations suggest that pectinolytic enzymes may only be weakly active when F. oxysporum strain Fo47 develops in E. viminalis roots, in contrast to those reported for root interactions with a pathogenic F. oxysporum strain that causes tissue disorganization and where pectin degradation appears to occur (Salerno et al 2004). Because both pathogenic and nonpathogenic strains of F. oxysporum can utilize pectin in pure culture (Steinberg et al 1999), differences in tissue degradation between Fusarium strains may be attributable to differential host control over their enzymatic activity, so enzyme repression occurs in one case but not in the other.…”

“…Slight, localized decrease in immunolabeling in the plant cell wall close to the hypha (arrow). Bar 0.5 µm effects on tissue integrity of E. viminalis roots differ greatly from those of a pathogenic F. oxysporum strain (Salerno et al 2004). This diversity does not strictly affect fungal virulence in E. viminalis seedlings because both fungi are able to intensely colonize E. viminalis roots (Salerno et al 2000).…”

“…In a study of interactions between E. viminalis and pathogenic F. oxysporum, the fungus greatly reduced the pectin component of cell walls during colonization of roots and ruptured the host plasma membrane, causing rapid host tissue and cell damage (Salerno et al 2004). The objectives of this study were to (1) investigate interactions between E. viminalis root tissues and nonpathogenic F. oxysporum strain Fo47 at the ultrastructural level and (2) elucidate possible reasons for the lack of disease development by studying distribution patterns of nonesterified (NE) and methyl-esterified (ME) pectin in E. viminalis root tissues in situ during root colonization.…”