Identification of a novel cis‐regulatory element for UV‐B‐induced transcription in Arabidopsis

Summary Ultraviolet‐B light (UV‐B) regulates the expression of genes in a wavelength‐ and fluence rate‐dependent fashion. A signaling pathway consisting of CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) and UV RESISTANCE LOCUS 8 (UVR 8) mediates responsiveness to longer wavelength, low intensity UV‐B light‐activating, for example, HY5 gene expression. By contrast, transcription of another group of genes, including ANAC13 , modulated by shorter wavelength, higher intensity UV‐B is controlled by a yet unknown and largely COP1‐independent signaling cascade. Here we provide evidence by promoter deletion analysis, and characterization of genetic mutants displaying aberrant expression patterns, that two cis‐regulatory elements, designated MRE ANAC13 and UVBox ANAC13 , are required for maximal UV‐B induction of the ANAC13 gene in transgenic plants. These elements are located in the proximal 150‐bp region of the ANAC13 promoter. They show no significant similarity to each other; the putative MRE ANAC13 (‐AACCTT‐) is closely related to MRE CHS (‐AACCTA‐) found in the CHALCONE SYNTHASE ( CHS ) gene, whereas UVBox ANAC13 (with core sequence CAAG) represents a novel cis‐regulatory element. The novel UVBox ANAC13 sequence is significantly enriched in the promoter region of a subset of UV‐B‐induced genes with similar activation properties as ANAC13 . In addition, we demonstrate that expression of a chimeric gene containing only the dimerized 12‐mer containing UVBox ANAC13 fused to a minimal CaMV35S promoter/luciferase reporter is (i) efficiently induced by shorter wavelength, higher intensity UV‐B, but (ii) does not respond either to longer wavelength UV‐B and red light or (iii) to abscisic acid treatment and osmotic, salt, heat and cold stresses.