Changes in carbohydrate coordinated partitioning and cell wall remodeling with stress-induced pathogenesis in wheat sheaths

Abstract

Plant cell walls are dynamic structures that undergo specific remodeling events during plant defence responses. Changes in the coordinated partitioning of carbohydrates between the cytosol and the extracellular milieu may direct sheath cell wall remodeling that occurs in a wheat–endophytic interaction with a Fusarium proliferatum ( F.p.) species. Increased levels of apoplastic myoinositol and glucose were apparent in the endophyte-positive F.p. -infected sheaths from asymptomatic greenhouse-grown wheat. The F.p. -infected plants exhibited a resistant-like response under conditions of host stress. Cellular concentrations of galactinol, glucose, fructose, sucrose and melibiose increased in wheat sheaths infected with the F.p. species compared to the non-infected control sheaths. In addition, the symptomatic F.p. -infected plants showed increased accumulation of arabinogalactans, syringyl lignin and ferulate dimers in the sheath epidermal walls in contact with the endophyte. These were distinct from the carbohydrate, lignin and ferulate deposition patterns in the non-infected control sheaths. Further examination of sheath walls in F.p. -infected and control wheat using laser scanning confocal microscopy revealed a distinct spectral emission profile localized to the epidermal walls in F.p. -infected plants that was concomitant with the enhanced deposition of wall-bound ferulates. Increased levels of total ferulate dimers, particularly the 8- O -4 and 5–5 linkages were found in the F.p. -infected compared to control sheaths.