Exhibits Kunitz trypsin protease inhibitor activity (PubMed:19825555). Involved in modulating programmed cell death (PCD) in plant-pathogen interactions (PubMed:19825555). Can inhibit both serine proteases and cysteine proteases (PubMed:30042779). May be involved in the modulation of the proteases that participate in the hydrolysis of dietary proteins in the gut of spider mites (PubMed:30042779). Expressed in roots. Down-regulated after root-knot nematode infection (PubMed:16236154). Accumulates locally within 72 hours after P.brassicae butterflies oviposition (PubMed:17142483). Induced late in response to bacterial and fungal elicitors (e.g. Pst DC3000 and Ecc culture filtrates), and upon wounding, salicylic acid (SA) and hydrogen peroxide H(2)O(2) treatments (PubMed:19825555). Induced by infestation with spider mites (PubMed:30042779). Enhanced lesion development after infiltration of leaf tissue with the programmed cell death (PCD)-eliciting fungal toxin fumonisin B1 (FB1) or the avirulent bacterial pathogen P.syringae pv. tomato DC3000 carrying avrB (Pst avrB). Enhanced resistance to the virulent pathogen E.carotovora subsp. carotovora SCC1. Belongs to the protease inhibitor I3 (leguminous Kunitz-type inhibitor) family. Truncated N-terminus.