Serine protease. Has a substrate preference for the hydrophobic residues Phe and Ala and the basic residue Asp in the P1 position, and for Asp, Leu or Ala in the P1' position. May play a role in the degradation of structural proteins in the extracellular matrix of cells located above sites of lateral root formation and thus facilitate lateral root emergence (By similarity). Expressed specifically at sites of lateral root emergence. Expressed during auxin-induced lateral root formation. Induced between 4 and 8 hours after treatment with auxin and remains high for at least 24 hours. Belongs to the peptidase S8 family.