Relative evolutionary rate for each site across four plant AGOs classes. (A) shows site specific relative evolutionary rates of AGOs across classes I-IV. Position-by-position (maximum likelihood) relative evolutionary rates are estimated under the JTT amino acid substitution model. Mean (relative) evolutionary rates are scaled such that the average evolutionary rate across all sites is 1. X-axis represent the positions of residues (620 residues) of the ‘AGO dataset II’ along the N-terminal, PAZ, MID and PIWI domains in AGO sequence. Y-axis shows the relative evolutionary rate. Sites showing rates <1 are evolving slower than average and those with rates >1 are evolving faster than average. (B) Threaded structures of NaAGO1a, NaAGO5, NaAGO2 and NaAGO4a are modeled as representatives of Classes I-IV respectively, and relative evolutionary rates are mapped on to these structures. Sites with green color represent slow evolving sites (rates <1) and those with red color represent fast evolving sites (rates >1). Different colors in the color bar represent the different rate values.