Classification based on C-termini of ACC synthases of tomato and Arabidopsis. ACC synthases can be grouped into three distinct types based on the similarity of their C-terminal amino acid sequences. The C-terminal amino acid sequences of ACC synthases were aligned using the CLASTALW program, drawn using MacBoxShade, and grouped into three distinct types. Eight ACC synthases from Arabidopsis (AtACS1, AtACS2, AtACS4, AtACS5, AtACS6, AtACS7, AtACS8, AtACS9, and AtACS11; AtACS3 is thought to be a pseudogene, and AtACS10 and AtACS12 are aminotransferases) and nine from tomato (LE-ACS1A, LE-ACS1B, LE-ACS2, LE-ACS3, LE-ACS4, LE-ACS5, LE-ACS6, LE-ACS7, and LE-ACS8) were aligned. Identical amino acids and conservative changes are indicated by reversed and shaded characters, respectively. The WVF and RLSF motifs and mutation sites for eto2-1 and eto3 are indicated.