( Pluto ( ( was ( ( called planet ) ( x ( before ( it ( was discovered ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Pluto)) (VP (VBD was) (VP (VBN called) (NP (NN planet)) (SBAR (NP (SYM x)) (IN before) (S (NP (PRP it)) (VP (VBD was) (VP (VBN discovered))))))) (. .)))
Pluto was called planet x before it was discovered.
(ROOT (S (NP (NNP Pluto)) (VP (VBZ is) (ADVP (RB now)) (VP (VBN called) (NP (NN dwarf) (NN planet)))) (. .)))