Figure 8.

Levels of the three BCAA-related 2-hydroxyacids are unchanged in the TaBCAT1 disruption mutant, but exogenous application of ILA severely perturbs Pst infection. A, Levels of the three BCAA-related 2-hydroxyacids (ILA, VA, and LA) were determined in the TaBCAT1 disruption mutant and Kronos wild-type plants in the absence of rust infection. Leaves from three independent plants were assessed in each case. B, Exogenous application of ILA 72 or 24 h prior to Pst infection dramatically reduced disease progression. Oakley plants were pre-treated with ILA at 0.5, 1, and 2 mM or with dH₂0 (0-mM ILA) 72 or 24 h prior to inoculation with Pst isolate 13/14 and infection types recorded 15-day post-infection using the 0–4 scale (McIntosh et al., 1995). Values represent an average from 10 plants per treatment, with the first (L1), second (L2), and third (L3) leaves analyzed. C, Histological studies using a fungus-specific fluorescent dye revealed that where internal fungal structures formed, their extension was only moderately reduced following ILA treatment at 0.5, 1, or 2 mM prior to Pst infection. D–G, Images illustrate the moderate reduction in Pst internal fungal structures when plants were treated with ILA 24 h prior to Pst infection. Scale bar represents 100 µm. S, urediniospore; GT, germ tube; SSV, sub-stomatal vesicle; IH, invasive hyphae. For the box plots, the bars represent median values, boxes signify the upper (Q3) and lower (Q1) quartiles, and whiskers are located at 1.5 the interquartile range