Transcription factor. Interacts specifically with the W box (5'-TTGAC[CT]-3'), a frequently occurring elicitor-responsive cis-acting element. Involved in defense responses. Required for resistance to the necrotrophic fungal pathogen B.cinerea (PubMed:17059405, PubMed:21990940). Regulates the antagonistic relationship between defense pathways mediating responses to the bacterial pathogen P. syringae and the necrotrophic pathogen B.cinerea (PubMed:17059405). Required for the phytoalexin camalexin synthesis following infection with B.cinerea. Acts as positive regulator of the camalexin biosynthetic genes PAD3 (CYP71B15) and CYP71A13 by binding to their promoters (PubMed:21498677, PubMed:22392279). Acts downstream of MPK3 and MPK6 in reprogramming the expression of camalexin biosynthetic genes, which drives the metabolic flow to camalexin production (PubMed:21498677). Functions with WRKY25 as positive regulator of salt stress response and abscisic acid (ABA) signaling (PubMed:18839316). Functions with WRKY25 and WRKY26 as positive regulator of plant thermotolerance by partially participating in ethylene-response signal transduction pathway (PubMed:21336597). The DNA-binding activity of WRKY33 is increased by SIB1 and SIB2 (PubMed:21990940). Interacts with MKS1 (PubMed:15990873). Interacts with ATG18A (PubMed:21395886). Interacts with SIB1 and SIB2 (PubMed:21990940). Interacts with VQ1 and VQ10 (PubMed:22535423). Highly expressed in roots, leaves and flowers, and at lower levels in stems, siliques and seeds. By salt stress (PubMed:18839316). Induced by infection with the necrotrophic fungal pathogen B.cinerea (PubMed:17059405, PubMed:21498677, PubMed:21990940). Induced by infection with the bacterial pathogen P.syringae pv. tomato DC3000 (PubMed:17059405). Phosphorylated by MPK4 (PubMed:15990873). Phosphorylated on serine residues by MPK3 and MPK6 following infection with the necrotrophic fungal pathogen B.cinerea (PubMed:21498677). No visible phenotype under normal growth conditions, but mutant plants are extremely susceptible to the necrotrophic fungal pathogen B.cinerea. Belongs to the WRKY group I family. Truncated N-terminus.