Infection induced oxidative cross-linking of hydroxyproline-rich glycoproteins (HRGPs) is associated with restriction ofColletotrichum sublineolumin sorghum

Abstract

Hydroxyproline-rich glycoproteins (HRGPs) accumulation and oxidative cross-linking is one of the earliest defense responses in plants against pathogen infection. In the present study HRGP accumulation in three sorghum genotypes i.e. SC146 (resistant), SC326 (intermediately resistant) and BTx623 (susceptible) as a response to Colletotrichum sublineolum isolate CP2126 infection is elucidated. HRGPs were monitored by hydroxyproline (Hyp) estimation. In genotypes SC146 and SC326 there was a significantly higher amounts of Hyp at 2 days after inoculation (dai) compared to genotype BTx623, indicating an infection induced accumulation of HRGPs. Western blot analysis of acid-ethanol extracted proteins with polyclonal antibody raised against pearl millet purified HRGPs identified four bands with molecular masses of Â65, 45, 17 and 14 kDa as HRGPs. Insolubilization of the 45 kDa protein in genotypes SC146 and SC326 upon infection with C. sublineolum indicates a role of this protein in cell wall cross-linking, coinciding with heavier accumulation of hydrogen peroxide. In addition, tissue print analysis using polyclonal antibody of pearl millet HRGPs recognized these cross-linked proteins to be HRGPs. These findings indicated that HRGPs in sorghum is a component of defense reaction against C. sublineolum infection.

Role of Protein Glycosylation in Host-Pathogen Interaction

“…HRGPs play a leading role in plant defense, e.g., HRGPs were induced in incompatible plant-pathogen interactions [18,89] and rapidly deposited in the cell wall after pathogen infection [90,91]. Such a defense ability is a result of the intra-and inter-molecular cross-linking in plant cell walls after HRGPs become insolubilized [88,92]. In this process, the interaction between insoluble HRGPs and the polysaccharide reduces the hydration and pectin mobility of the cell wall thus leading to the increase of rigidity and resistance of cell wall against pathogen invasion [92].…”

“…Such a defense ability is a result of the intra-and inter-molecular cross-linking in plant cell walls after HRGPs become insolubilized [88,92]. In this process, the interaction between insoluble HRGPs and the polysaccharide reduces the hydration and pectin mobility of the cell wall thus leading to the increase of rigidity and resistance of cell wall against pathogen invasion [92]. Furthermore, it was found that intra-and inter-molecular cross-linking took place in glycosylated HRGPs under the catalysis of the peroxidase.…”

The Role of Plant Cell Wall Proteins in Response to Salt Stress

“…According to several authors [69–71], extensins undergo peroxidase-mediated oxidative cross link during pathogen infection thus decreasing the permeability of the cell wall. Similar effect was also proposed for at least some AGPs classes [72].…”

Pre-harvest spray of oligochitosan induced the resistance of harvested navel oranges to anthracnose during ambient temperature storage

“…HRGP contents were assessed according to the method of Basavaraju et al (2009) and Shailasree et al (2004) with slight modifications. To prepare the cell wall, the orange rinds (1 g) were homogenized using a pestle and mortar at 4 C in 100 mM phosphate buffer at pH 7.2.…”