Figure 5.

Exogenous Application of l-Homoserine Leads to H. arabidopsidis Resistance in Arabidopsis.

(A) Infiltration of H. arabidopsidis–infected seedlings with l-homoserine (5 mM) leads to resistance to H. arabidopsidis, whereas treatment with 5 mM of l-Met, l-Thr, l-Ile, or d-homoserine does not reduce the level of H. arabidopsidis sporulation. The average number (with sd, n = 30) of conidiophores/seedling is displayed. The results were confirmed in two additional independent experiments.

(B) A high frequency of papillae formation, visible as translucent encasements surrounding the trypan blue–stained haustoria, is observed in l-homoserine (L-HS)–treated seedlings and not after treatment with the other amino acids or the d-stereo-isomer of homoserine. Bars = 10 μm.