Flagging defensive roles of carbohydrate-active enzymes (CAZymes) and carbohydrates during Puccinia triticina-wheat interactions

Abstract

Puccinia triticina (Pt) infects wheat, leading to colonization of leaf tissues, pustule formation on the leaf and eventually yield loss. Fungicides and breeding techniques are used to manage Pt infection in wheat. However, there is a growing need for biochemical studies to identify critical metabolites and proteins that contribute to plant susceptibility or resistance against Pt. The current study investigated defensive role of non-structural, structural carbohydrates, and CAZymes during Pt-wheat interaction at 1, 7, and 14 days post inoculation (dpi). The results revealed that glucose, total reducing sugars and sucrose were significantly decreased by more than 50% in Pt inoculated susceptible Thatcher (IS) plants. Sucrose concentrations decreased by 0.80 and 0.93 fold in IS compared to control sample (CS) at 1 and 7 dpi. Pt inoculated resistant Thatcher + Lr9 (IR) plants and control (CR) did not display differences in soluble carbohydrate concentrations. In addition, exoglucanase, endoglucanase, pectinase and carbohydrate esterase activities were significantly higher at 1 or 7 dpi in IS compared to IR plants. The cellulose-content was 29% in IR samples compared to 15% in CR samples at 14 dpi. Additionally, hemicellulose increased by 2% in IR at 14 dpi. The cell wall reinforcements in resistant plants were supported by Fourier transformation infrared results that revealed that IR holocellulose content was not affected by Pt infection, but IS samples holocellulose decreased at 7 dpi. In conclusion, increased activities of CAZymes, decreased cell wall holocellulose content, and reduced soluble carbohydrates were susceptibility indicators.