elucidating-13-glucanase-peroxidase-physicochemical-properties-wheat

Elucidating &#946;-1,3-Glucanase and Peroxidase Physicochemical Properties of Wheat Cell Wall Defense Mechanism Against <i> Diuraphis noxia</i> Infestation

Wheat plants infested by Russian wheat aphids (RWA) induce a cascade of defense responses, including the hypersensitive responses (HR) and induction of ...

university of the free state

Elicitors are molecules which can induce the activation of plant defence responses. Elicitor activity of intercellular wash fluid from Russian wheat aphid, Diuraphis noxia (Mordvilko) infested resistant (cv Tugela DN), and susceptible (cv Tugela), wheat (Triticum aestivum L.), was investigated. Known Russian wheat aphid resistance related responses such as peroxidase and beta-1,3-glucanase activities were used as parameters of elicitor activity. The intercellular wash fluid from infested resistant plants contains high elicitor activity while that from infested susceptible plants contains no or very little elicitor activity. After applying C-18 reverse phase and concanavalin A Sepharose chromatography, elicitor active glycoproteins were isolated from the intercellular wash fluid of Russian wheat aphid infested resistant wheat. The elicitor-active glycoproteins separated into three polypeptides during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isolated glycoproteins elicited peroxidase activity to higher levels in resistant than in susceptible cultivars. It was evident that the glycoproteins were probably a general elicitor of plant origin. Information gained from these studies is valuable for the development of plant activators to enhance the defence responses of plants.

Glycoproteins from Russian wheat aphid infested wheat induce defence responses.

Russian wheat aphid (RWA) is one of the most challenging pests for wheat crops globally. In South Africa, RWA has breached the strategy of introducing resistant genes into wheat plants, and so far, five RWA biotypes with different virulence levels have been documented in the field. Our study investigated how the cell wall plays a defensive role in Tugela-Dn1 (susceptible) and-Dn5 (resistant) cultivars infested with South African RWA-biotype 2 (RWASA2). The activities of enzymes related to defense responses were measured. The cell wall's holo-cellulose content, soluble lignin and physicochemical changes were quantified in the infested susceptible and resistant cultivars. Lastly, in vitro RWASA2 saliva-associated CWDEs activity was determined on cell wall-related model substrates. The results show that apoplastic peroxidase and β-1,3-glucanase activities were significantly higher in Tugela-Dn5 relative to the control during the infestation periods. Peroxidase activity is associated with lignin cross-linking of the cell wall, which could deter RWASA2 feeding. The total phenolic and holo-cellulose contents were significantly induced in Tugela-Dn5 at 72 and 120 h post infestation (hpi). These findings were corroborated by the FTIR results, which showed that holocellulose and lignin regions of the resistant and susceptible wheat were affected by infestation at 72 hpi. However, Tugela-Dn5 reinforced cell wall content at 120 hpi. An increased crystallinity index in the resistant cultivar validated the cell wall reinforcement at 120 hpi, while Tugela-Dn1 delayed cell wall reinforcement. This study demonstrates that cell wall reinforcement's modification is part of defense responses against Russian wheat aphid infestation.

Cell-wall structural carbohydrates reinforcements are part of the defence mechanisms of wheat against Russian wheat aphid (Diuraphis noxia) infestation.

Lintle Mohase

Faculty of Natural and Agricultural Sciences,
Department of Plant Science,
Botany,
Plant Biochemistry and Physiology,
Faculty of Natural and Agricultural Sciences, Department of Plant Science, Botany, Plant Biochemistry and Physiology

university of the free state

Elucidating β-1,3-Glucanase and Peroxidase Physicochemical Properties of Wheat Cell Wall Defense Mechanism Against Diuraphis noxia Infestation