Functional characterization of a defense-related class-III chitinase promoter from Lupinus albus, active in legume and monocot tissues

Abstract

A class-III chitinase promoter was isolated from Lupinus albus. The region 5′ to the coding sequence of the IF3 gene was amplified by gene walking and sequenced. The proximal 2.0 kb sequence contains a predicted promoter site, including a TATA box, near the ATG start site. To test for minimal sequences needed for promoter activity, the region was restricted into fragments of 1.81, 1.51 and 1.13 kb and cloned into the pDM327 vector, upstream from the bar-gus fusion gene for Biolistic™ transformation. Transformation of lupin embryos, bean callus tissue, maize embryos and Ornithogalum callus demonstrated promoter activity for all fragments. In silico analysis identified putative cis-acting elements in the 1.81 kb fragment that could be important in controlling gene expression. Fungal elicitor activated-, woundinducible- and ethylene responsive elements were present in the 1.51 kb fragment. Myb elements and CAAT boxes that regulate responses to environmental factors and modulate promoter efficiency were identified in the 1.81 kb fragment. The 1.51 and 1.81 kb fragments were inserted upstream of the gus gene into the pBI121 vector for Agrobacterium tumefaciens transformation of tobacco. Quantitative GUS assays indicated that the promoter fragments are functional in planta and inducible by defense-related signals, wounding, as well as chemical elicitation. All important elements essential for Bion inducibility are present on the shorter (1.51 kb) promoter fragment, but both 5′ distal and proximal cis-elements are required for full functionality. The IF3 promoter is, thus, suitable for use in defense gene constructs prepared for the production of anthracnose resistant lupin.