Structural Characterization of Oligochitosan Elicitor from Fusarium sambucinum and Its Elicitation of Defensive Responses in Zanthoxylum bungeanum

Abstract

Oligosaccharide elicitors from pathogens have been shown to play major roles in host plant defense responses involving plant–pathogen chemoperception and interaction. In the present study, chitosan and oligochitosan were prepared from pathogen Fusarium sambucinum, and their effects on infection of Zanthoxylum bungeanum stems were investigated. Results showed that oligochitosan inhibited the infection of the pathogen, and that the oligochitosan fraction with a degree of polymerization (DP) between 5 and 6 showed the optimal effect. Oligochitosan DP5 was purified from fraction DP5-6 and was structurally characterized using electrospray ionization mass spectrometry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Oligochitosan DP5 showed significant inhibition against the infection of the pathogenic fungi on host plant stems. An investigation of the mechanism underlying this effect showed that oligochitosan DP5 increased the activities of defensive enzymes and accumulation of phenolics in host Z. bungeanum. These results suggest that oligochitosan from pathogenic fungi can mediate the infection of host plants with a pathogen by acting as an elicitor that triggers the defense system of a plant. This information will be valuable for further exploration of the interactions between the pathogen F. sambucinum and host plant Z. bungeanum.

Molecular Mechanisms of Chitosan Interactions with Fungi and Plants

“…Very low concentrations (picomolar; pM) of chitin oligomers can still trigger PTI [106]. Chitin oligomers with large degrees of acetylation and polymerisation induce main PTI responses (ROS production and alkalinisation) [107,108,109]. Chitosan induces callose deposition in plants [110].…”

Chitin and chitin-related compounds in plant–fungal interactions

“…It was found that chitosan amendment increased plant phenylalanine ammonia lyase activity, which is the crucial enzyme of phenylpropanoid metabolism, and the subsequent increase in phenolic content, polyphenol oxidase, peroxidase, and chitinase is a general response associated with disease resistance (Anand et al 2009; Mejía-Teniente et al 2013). The use of oligo-chitosan with the degree of polymerisation of five significantly enhanced defensive activities of all four enzymes (Li et al 2016). Chitosan was also found to increase the production of glucanohydrolases, specific phytoalexins with antifungal activity and of lignin-like material and reduced macerating enzymes such as polygalacturonases and pectin methylesterase (Ali et al 2014).…”

“…Moreover, chitosan induces proteinase inhibitors (Walker-Simmons and Ryan 1984), phytoalexin biosynthesis (Hadwiger and Beckman 1980) and callose formation (Köhle et al 1985) in dicot species. The plants’ response to chitin, chitosan and the derived oligosaccharides depends on the acetylation degree (Akiyama et al 1995; Cord-Landwehr et al 2016; Li et al 2016) and the degree of polymerisation (Walker-Simmons and Ryan 1984; Li et al 2016). of these compounds.…”

RNA-seq and metabolome revealed counter effect of chitosan against Botrytis cinerea on grape berries

“…Oligosaccharide growth elicitors from various pathogens reported having a critical role in host plant protection mechanism encompassing plant pathogen chemoperception chemoperception and interaction [15].…”