Heat Shock Factors HsfB1 and HsfB2b Are Involved in the Regulation of Pdf1.2 Expression and Pathogen Resistance in Arabidopsis

• DOI: 10.1093/mp/ssn095
• Publication Date: 2009-01-29T02:01:26Z
• Authors: Mukesh Kumar; Wolfgang Busch; Hannah Birke; Birgit Kemmerling; Thorsten Nürnberger; Friedrich Schöffl
• Keywords: 0303 health sciences; Base Sequence; Arabidopsis Proteins; Gene Expression Profiling; Arabidopsis; Electrophoretic Mobility Shift Assay; Plant Science; Genes, Plant; Polymerase Chain Reaction; Defensins; Gene Knockout Techniques; 03 medical and health sciences; Gene Expression Regulation, Plant; Molecular Biology; Heat-Shock Proteins; DNA Primers

In order to assess the functional roles of heat stress-induced class B-heat shock factors in Arabidopsis, we investigated T-DNA knockout mutants of AtHsfB1 and AtHsfB2b. Micorarray analysis of double knockout hsfB1/hsfB2b plants revealed as strong an up-regulation of the basal mRNA-levels of the defensin genes Pdf1.2a/b in mutant plants. The Pdf expression was further enhanced by jasmonic acid treatment or infection with the necrotrophic fungus Alternaria brassicicola. The single mutant hsfB2b and the double mutant hsfB1/B2b were significantly improved in disease resistance after A. brassicicola infection. There was no indication for a direct interaction of Hsf with the promoter of Pdf1.2, which is devoid of perfect HSE consensus Hsf-binding sequences. However, changes in the formation of late HsfA2-dependent HSE binding were detected in hsfB1/B2b plants. This suggests that HsfB1/B2b may interact with class A-Hsf in regulating the shut-off of the heat shock response. The identification of Pdf genes as targets of Hsf-dependent negative regulation is the first evidence for an interconnection of Hsf in the regulation of biotic and abiotic responses.