GO terms associated with unigenes in expression cluster 4. (A) K-means clustering was used to visualize the expression pattern of unigenes in cluster 4. Expression decreased from 0 to 48 h after inoculation. Unigenes were annotated with GO terms corresponding to (B) biological processes, (C) molecular functions, and (D) cellular components. Pie charts represent the distribution of unigenes annotated with each GO term.