Alternative splicing (AS) regulator that binds to specific mRNAs and modulates auxin effects on the transcriptome. Displaced from its targets upon binding to AS competitor long non-coding RNA (ASCO-RNA). Relocalizes to cytoplasmic bodies in trichoblast cells containing root hairs or when coexpressed with Medicago ENOD40 RNA. Isoform 1: Expressed in root meristems, lateral root primordia, root vascular tissues and cotyledon vascular tissues. Isoform 2: Expressed in root meristems, lateral root primordia and root vascular tissues. Up-regulated by auxin treatment. No visible phenotype. Nsra and nsrb double mutants are less sensitive to auxin.