Structure and function of wall appositions. 1. General histochemistry of papillae in barley coleoptiles attacked by Erysiphe graminis f. sp. hordei

Abstract

Penetration pegs of Erysiphe graminis D.C. f. sp. hordei Em. Marchal are usually not impeded by normal papillae of barley coleoptiles, whereas oversize papillae are impenetrable to appressoria of the pathogen. We investigated the chemical composition of these papillae and the cell walls by classical histochemistry, in part to extend the fragmented knowledge of these structures and in part to find out if there are differences between normal and oversize papillae which would account for their different efficacies in resisting penetration. These papillae were indistinguishable from one another histochemically and contained protein, carbohydrate other than pectin, and a phenolic which was not lignin. We report also a definitive proof of callose in papillae. They do not contain cutin or suberin. The cell wall did not contain callose or cutin–suberin but did contain protein, pectin, and a phenolic (also not lignin). The results imply that different linkages between molecules in oversize papillae, or some other differences not revealed in this study, are responsible for their ability to prevent fungal penetration.

Ultrastructural and histochemical studies on interactions between Vitis vinifera L. and Uncinula necator (Schw.) Burr.

“…A 1'5 % aqueous solution containing 1-5 % concentrated ammonia was boiled for 10 min. Material was treated for 30-60 min with the cooled stain and rinsed (modified after Smart et al, 1986a).…”

An Arabidopsis Callose Synthase, GSL5, Is Required for Wound and Papillary Callose Formation

“…Particular attention has been focused on callose formation in plantmicrobe interactions, during which plant host cells respond to microbial attack by rapidly synthesizing and depositing callose as plugs, drops, or plates in close proximity to the invading pathogen (Ryals et al, 1996;Donofrio and Delaney, 2001). These callosic deposits are commonly referred to as papillae and are thought to contain, in addition to (1 → 3)-␤ -D -glucan, minor amounts of other polysaccharides, phenolic compounds, reactive oxygen intermediates, and proteins (Smart et al, 1986;Bolwell, 1993;Bestwick et al, 1997;ThordalChristensen et al, 1997;Heath, 2002). Although the precise function of callosic papillae during microbial attack has not been demonstrated unequivocally, it has been postulated that the papillae act as a physical barrier to impede microbial penetration (reviewed by Stone and Clarke, 1992).…”

The Multivesicular Body-Localized GTPase ARFA1b/1c Is Important for Callose Deposition and ROR2 Syntaxin-Dependent Preinvasive Basal Defense in Barley

“…A number of other constituents have been described in barley papillae. These include a phenolic conjugate, p-coumaroylhydroxyagmatine (von Rö penack et al, 1998), H 2 O 2 , cell wall cross-linked proteins (Thordal-Christensen et al, 1997), iron (Fe 3+ ) (Liu et al, 2007), and cell wall cross-linked phenolics (Smart et al, 1986). Meanwhile, the b-1,3-glucan polymer, callose, is the most well-studied component of the papilla, and it is often used as a marker for papilla formation.…”

“…Since the structure of the papilla remains intact in the Arabidopsis pmr4 callose-negative mutant, a structural scaffold constituent must exist in addition to callose (Jacobs et al, 2003;Nishimura et al, 2003). However, histochemical analyses of the major cell wall constituents, cellulose and pectin, have been negative in barley (Smart et al, 1986), implying that these are not part of the papilla structure.…”