Arabidopsis BRCA2 and RAD51 proteins are specifically involved in defense gene transcription during plant immune responses

Abstract

Systemic acquired resistance (SAR) is a plant immune response associated with both transcriptional reprogramming and increased homologous DNA recombination (HR). SNI1 is a negative regulator of SAR and HR, as indicated by the increased basal expression of defense genes and HR in sni1. We found that the sni1 phenotypes are rescued by mutations in BREAST CANCER 2 (BRCA2). In humans, BRCA2 is a mediator of RAD51 in pairing of homologous DNA. Mutations in BRCA2 cause predisposition to breast/ovarian cancers; however, the role of the BRCA2-RAD51 complex in transcriptional regulation remains unclear. In Arabidopsis, both brca2 and rad51 were found to be hypersusceptible not only to genotoxic substances, but also to pathogen infections. A whole-genome microarray analysis showed that downstream of NPR1, BRCA2A is a major regulator of defense-related gene transcription. ChIP demonstrated that RAD51 is specifically recruited to the promoters of defense genes during SAR. This recruitment is dependent on the SAR signal salicylic acid (SA) and on the function of BRCA2. This study provides the molecular evidence showing that the BRCA2-RAD51 complex, known for its function in HR, also plays a direct and specific role in transcription regulation during plant immune responses.suppressor of sni1 3 | tiling array-based cloning | plant fertility | transcription-associated DNA damage | chromatin remodeling

Up-regulation of the interferon-related genes in BRCA2 knockout epithelial cells

“…Our CHIP assay showed that EMSY still binds to the promoter of IFN-stimulated genes in the absence of BRCA2, suggesting that the regulation of IFN-related genes by BRCA2 complex is independent of EMSY's chromatin binding capacity. CHIP result in Arabidopsis demonstrated that another BRCA2 interaction protein, RAD51, was recruited to the promoters of defence genes during plant immune response [8]. However, in our study, when RAD51 was over-expressed, it did not modulate IFN-α induced ISRE activity (in contrast with BRCA2 expression) ( Figure 5b).…”

“…BRCA2 forms a complex with Smad3 and synergizes in regulating the transcription of Smad3-dependent luciferase reporters [7]. In Arabidopsis, BRCA2 is a major regulator of immune gene transcription [8]. In human cells, the expression of two innate immunity genes (UCRP and UBE2L6) were down-regulated after BRCA2 knock down [9].…”

CRT1 is a nuclear-translocated MORC endonuclease that participates in multiple levels of plant immunity

“…For instance, SNI1 (Suppressor of NPR1, Inducible) was proposed to mediate defence gene expression via histone modification 44 . Interestingly, several ssn mutants encode mutated versions of well-established DNA R/R proteins, such as RAD51D (SSN1), SWI/SNF (SSN2) and BRCA2A (SSN3) 30,45,46 . Mutations in any of the three SSN genes results in altered induction of pathogen-responsive genes and increased susceptibility/sensitivity to pathogens and DNAdamaging agents.…”

Perception of volatiles produced by UVC-irradiated plants alters the response to viral infection in naïve neighboring plants

“…7 Since ROS production is associated with the formation of necrotic lesions, it is possible that the increase in HRF in distal tissue is due to ROS signaling or ROS-induced signaling through MeJA, MeSA or other volatile molecules. The link between salicylic acid signaling and homologous recombination is well established, 8 although it is not clear whether it has any direct biological significance. It is possible that the upregulation of PR1 expression in bystander plants is a consequence of shared signaling pathways in response to abiotic and biotic stresses.…”