(1→3)-α-D-glucooligosaccharides as Elicitors Influencing the Activity of Plant Resistance Pathways in Wheat Tissues

Abstract

Laetiporus sulphureus (Bull.: Fr.) Murrill is an arboreal species of the large-fruited Basidiomycota fungus from the Polyporales, family Laetiporaceae. The cell wall of this fungus is the source of many bioactive polymer compounds, including (1→3)-α-D-glucans. (1→3)-α-D-glucans can be hydrolyzed to shorter compounds, (1→3)-α-D-glucooligosaccharides (GOS), with different degrees of polymerization (DP). The use of GOS obtained from L. sulphureus (1→3)-α-D-glucans, as an elicitor of plant resistance, may be important for biological protection used in sustainable agriculture. In the presented study, GOS influenced the activity of antioxidant enzymes (Catalase−CAT, Ascorbate Peroxidase−APX, Guaiacol Peroxidase−GPX, and Superoxide Dismutase−SOD), lignin and flavonoids producing phenylpropanoids pathways (Phenylalanine Ammonia-Lyase−PAL and Tyrosine Ammonia-Lyase−TAL), and pathogen-related proteins (with Glucanase−GLUC and Chitinase−CHIT activity) in wheat (Triticum aestivum L.) seedling tissues. Other than that, the application of GOS increased the fresh weight of wheat stems and roots by 1.5–2-times, compared to the water control. The GOS at a concentration of 0.05% most strongly increased the activity of APX and GPX, where a 2-fold (up to 6000 U) and a 3-fold (up to 180 U) increase in enzymatic activity in wheat stems was observed, compared to the control. Simultaneously, 0.1% GOS significantly increased the activity of PAL (80 U in stems and 50 U in roots) and TAL (60 U in stems and 50 U in roots), where a 4–5-fold increase in enzymatic activity was observed, both in comparison to the water control and commercial elicitors (chitosan−CHI and laminarin−LAM). No effect of GOS on GLUC activity was observed, but a 1.5–2-fold increase in CHIT activity in plant tissues was noted. The complexity of the influence of GOS on the level of marker enzymes indicates the potential of their application in agriculture. This work is the first report of the successful use of (1→3)-α-D-glucooligosaccharides as an elicitor inducing resistance in the cereal plant (wheat).