Aspects of ß-1,3-glucanase expression in wheat associated with Russian wheat aphid resistance
Wilding, Willem Jacobus Marthinus
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The aim of the study was to learn more about the expression of b-1,3-glucanase during the resistance response of wheat to the RWA (Diuraphis noxia)(Mordvilko). The different resistance genes (Dn1, Dn2 and Dn5) used in the study would shed more light on the possibility that b-1,3-glucanase expression is a universal biochemical resistance mechanism with regard to RWA. Tugela DN (Dn1) and Dn2 plants resulted in a similar expression pattern of b-1,3-glucanases after RWA infestation. The Dn1 and Dn2 cultivars had very high differential b-1,3-glucanase activity induction, which occurred much sooner compared to the infested susceptible plants. Wheat plants with the Dn5 resistance gene induced b-1,3-glucanase activity to a much lower level compared to the other two resistant lines. Northern blot analyses confirmed that the increase in b-1,3-glucanase activity and peptide levels in the Western blot analyses was due to increased transcription of b-1,3-glucanase genes. The induced b-1,3-glucanases were located intercellularly in the vascular bundle and mesophyll cell walls of wheat leaves. Intracellular the b-1,3-glucanases were primarily located in the chloroplast grana with low labelling found in the cytoplasm. Chloroplasts were isolated and fractionated to scrutinize results obtained with the localisation study. b-1,3-glucanase activity and Western blot analysis of chloroplast fractions verified these results with a 35 kDa b-1,3-glucanase residing in the chloroplast membrane bound fraction. These b-1,3-glucanases could play a role in the protection of the chloroplast of infested resistant plants.