Tissue invasion and alteration in eggplant infected with Verticillium dahliae: A light and transmission electron microscopy study

Abstract

Light and transmission electron microscopy observations of Verticillium-inoculated eggplants are reported. Results of tests for cellulose and chitin are also presented. Opaque, vessel wall lining matter (VWLM) generally occurred, connected to elements identified as fungal cells, and extending into vessel secondary walls and across pits. VWLM was also confluent with similar matter extensively pervading middle lamellae and causing their alterations. The thickest VWLM was stratified as alternating opaque and more lucent bands, with the opaque ones being similar to the first layer deposited. Many loops were included in or bulged from the VWLM layers. Lace-like structures also occurred in vessel lumina as apparent distensions of the basic, first opaque layer of this VWLM. Large amounts of similar opaque matter occurred in the periphery of paratracheal cells with altered content. This matter contained filamentous-like structures and frequently opaque particles reminiscent of ribosomes. The pitted areas were much altered as an internal shred-like network, unlabelled for cellulose, covered by an outer opaque and compact cellulose-labelled layer, itself overlaid by an unlabelled VWLM. Release of labelled material from these altered areas only occurred at locations of VWLM ruptures. Detachment and alterations of the adjacent vessel wall secondary thickenings were noticeable and accounted for the presence of lucent cellulose-labelled matter in vessel lumina.Un objectif de cette étude a été de caractériser, dans des plants inoculés, les composantes exogènes aux éléments de vaisseaux, dont les enduits sur la paroi vasculaire, et leurs liens avec des altérations cellulaires et la présence de matière opaque dans les lamelles mitoyennes et le périplasme de cellules paratrachéales. Des tests pour localiser certains composés pariétaux ont été utilisés. Les enduits étaient formés de diverses couches, dont une première, mince et opaque et d’aspect membranaire, et d’autres plus épaisses et translucides alternant avec des couches opaques. Plusieurs gonflements circulaires se trouvaient dans ou à la marge de ces strates (VWLM). D’autres réseaux sinueux, apparemment issus de l’espacement des bandes formant la première couche de l’enduit, se trouvaient dans les vaisseaux. La matière périplasmique contenait des structures filamenteuses et de nombreuses particules opaques d’allure ribosomique. La partie interne des champs de ponctuations montrait des bandes opaques éparses, non marquées pour la cellulose, recouverte d’une couche plus compacte, marquée pour ce substrat. Les résidus altérés n’étaient libérés dans les vaisseaux qu’en cas de rupture du VWLM montrant l’absence de marquage pour ces deux substrats. Les épaississements secondaires des parois vasculaires étaient souvent altérés ou détachés de leur base, expliquant la présence de matière translucide marquée pour la cellulose dans les vaisseaux

A Review of Ultrastructural and Ultracytochemical Studies of Infection Processes in Some Plant Wilt Diseases: The Opaque Matter Extensively Involved, Its Links with Pathogen Elements, Insights into Its Nature

“…In these, pit membrane alterations and intercellular spaces may also become distended and degraded in conjunction with material con-nected to the lining, as it occurs regularly in the other hosts studied, where the OM in the distended pit membranes shows connection with the lining~Fig. 3A,C; Ouellette, 1978b;Ouellette & Rioux, 1992, 1993Ouellette et al, 2004d, 2008bOuellette & Chamberland, 2006; Figs. 3B and C1,C2 are enlarged portions thereof and will be referred to hereon!.…”

“…1A; Ouellette, 1978b;Ouellette & Chamberland, 2006!. 1A; Ouellette, 1978b;Ouellette & Chamberland, 2006!.…”

“…1A; Ouellette, 1978b;Ouellette & Chamberland, 2006!. Thicker linings may subsequently form, then occurring generally as alternating layers of opaque and more lucent layers, the layer apposed to vessel walls always being opaque~Ouellette, 1978b; Ouellette & Rioux, 1993;Ouellette et al, 2002Ouellette et al, , 2004bOuellette et al, , 2004e, 2005aOuellette & Chamberland, 2006!. 1B; Ouellette & Rioux, 1992!.…”

“…A noteworthy feature is that alterations of pathogen cells in these plants may identify with the presence of pectin compounds~Chamberland, 1994;Ouellette et al, 2004a!. Other features related to the lining may be mentioned: cellulose-labeled material in vessel lumina, traceable mostly to altered pit membranes or pit fields in protoxylem and metaxylem vessel elements~in elms, eggplant, staghorn sumac!, occurs only when the lining, unlabeled, is ruptured Ouellette et al, 2005a, Ouellette & Chamberland, 2006 in the susceptible carnation plants, numerous small, uniform particles occur in the lining, which can aggregate into paracrystalloids~Ouellette et al, 2004c! In the carnation resistant Novada cultivar, these compounds may be abundant in reacting tissue and be secreted through disorganized paratracheal and vessel walls~Ouellette et al, 2008b-Chap.…”

“…V!. 4B,C,E!, in repeated inoculations of elms, staghorn sumac, and egg-plant~Ouellette, 1978c; Ouellette et al, 2005b;Ouellette & Chamberland, 2006!. 3B-E!.…”