The GH28 family of polygalacturonases. The tree includes GH28 proteins from Arabidopsis (AT), rice, Brachypodium (Bradi), sorghum, poplar, and maize. Tree construction and color-coding (blue for eudicots and red for grasses) are as in Figure 2. For several branches, the percent of bootstrap replicates supporting the branch is indicated. Dotted and solid gray lines mark groups according to the designations of Penning et al. . Small gray arrows indicate proteins corresponding to genes - QRT2, ADPG1 and ADPG2 in group D and At1g48100 in group C - characterized by Ogawa et al. . A gray asterisk marks a clade of grass sequences that does not fall into any of the other groups. For clarity, names are shown only for selected Arabidopsis and Brachypodium genes. For complete branch labels and bootstrap values, see additional file 14.