Figure 3.

A hypothesis of gall formation processes in various host plants. Common candidate genes for stem cell generation and floral organ development were extracted from transcriptome data of developing galls of A. montana, G. obovatum [7], R. javanica [40] and V. riparia [60]. The thickness of arrow indicates the expression level of each gene. The gall formation hypothesis explains the gall formation mechanism that sepal and carpel-based galls are generated by the ectopic over expression of class-A, class-B, and class-E floral homeotic genes on leaves in A. montana and R. javanica, or carpel-based gall is generated by the expression of class-C and E genes in V. riparia. No floral homeotic genes need for generation of pouch-type thin gall of E. japonica.