sentence: Plants and green algae lack orthologs of the metazoan GW182 / TNRC6 proteins and , in A. thaliana , the known factors required for miRNA-mediated translation inhibition include the microtubule-severing enzyme KATANIN1 , decapping enhancer VARICOSE , GW-containing protein SUO , endoplasmic reticulum ( ER ) membrane protein ALTERED MERISTEM PROGRAM1 , and dsRNA-binding protein DRB2 ( 2 , 4 , 15 , 16 ) .