Transcriptional activator involved in defense responses against pathogens (PubMed:17601827, PubMed:19700558, PubMed:21726399). Acts as positive regulator of defense responses against the rice blast fungus Magnaporthe oryzae (PubMed:17601827, PubMed:19700558, PubMed:21726399). Acts through W-boxes, which are cis-elements that are enriched in the promoters of several defense-related genes (PubMed:17601827). Plays an important role in the benzothiadiazole-induced disease resistance by mediating salicylic acid (SA) defense signaling pathway, independently of the disease resistance gene NPR1/NH1 (PubMed:17601827, PubMed:21726399). Acts as negative regulator of defense responses against the bacterial blight Xanthomonas oryzae pv oryzae (Xoo) and the bacterial streak Xanthomonas oryzae pv oryzicola (Xoc) (PubMed:19700558). Acts downstream of abscisic acid (ABA) signaling in response to the rice blast fungus (PubMed:20459318). ABA is a negative regulator of defense responses that interacts antagonistically with salicylic acid (SA) signaling pathway (PubMed:20459318). Acts as negative regulator of ABA signaling that suppresses growth of seedlings (PubMed:21725029). Does not seem to be involved in the regulation of salt stress response (PubMed:21725029). Acts as negative regulator of cold stress response (PubMed:21725029). Acts as negative regulator of drought stress response (PubMed:21725029). Expressed in aleurone cells. Induced by abscisic acid (ABA) in aleurone cells (PubMed:15618416). Induced by salicylic acid (SA) and infection with the rice blast fungus Magnaporthe oryzae (PubMed:16528562). Induced by benzothiadiazole (BTH) and salicylic acid (SA) (PubMed:17601827). Induced by cold stress (PubMed:21725029). Down-regulated by drought stress (PubMed:21725029). No visible phenotype under normal growth conditions, but mutant plants are compromised in benzothiadiazole-induced resistance to the rice blast fungus Magnaporthe oryzae (PubMed:17601827). Enhanced resistance to the bacterial blight Xanthomonas oryzae pv oryzae (Xoo) and the bacterial streak Xanthomonas oryzae pv oryzicola (Xoc) (PubMed:19700558). Enhanced resistance to bacterial pathogens is associated with increased accumulation of salicylic acid (SA) and jasmonate (JA) (PubMed:19700558). Plants overexpressing WRKY45 exhibit enhanced resistance to the rice blast fungus Magnaporthe oryzae (PubMed:17601827, PubMed:19700558). Plants overexpressing WRKY45 exhibit increased susceptibility to the bacterial blight Xanthomonas oryzae pv oryzae (Xoo) and the bacterial streak Xanthomonas oryzae pv oryzicola (Xoc) (PubMed:19700558). Belongs to the WRKY group III family. Rice plants contain two different alleles of WRKY45, WRKY45-1 (AC Q5W6D6) and WRKY45-2 (AC B8AWM1), which play similar and opposite roles in defense response, response to abscisic acid (ABA) and response to abiotic stresses.